Pedestrian-Level Wind Environment Assessment of Shenyang’s Residential Areas through Numerical Simulations

Round 1

Reviewer 1 Report

The novelty of this paper is significant enough to publish on “Sustainability”. Thus, my decision is an acceptance

Author Response

Dear editors and reviewers:

Thank you very much for your letter, and the referees’ reports.

Author Response File: Author Response.docx

Reviewer 2 Report

The theme and approach presented in the paper are not innovative (and not even recent) - the need has in fact been known since the time of Vitruvius: … “Streets or public ways ought therefore to be so set out, that when the winds blow hard their violence may be broken against the angles of the different divisions of the city, and thus dissipated” (cfr.de Architectura, Book VI).

Despite this and also thanks to the evolution over time of the tools for simulations (see fluent), the paper - which analyzes a specific case - to be concretely useful should have as main objective to turn to the authorities of the construction departments of Shenyang and only afterwards to turn to designers and urban planners.

With this in mind, the text should be much more concise in the references on the state of the art, eliminate some repetitions, but above all present the results of the simulations in tables (such as in Table 1 The building arrangements for the simulation), or graphic diagrams. In this way the results would be easy and immediate to read.

The results presented in the current discursive way do not allow to have an overall picture of the potential and criticality of each of the 12 kinds of layouts analyzed: which layouts and with which types of buildings are the most critical in winter / summer? What are the most favorable slab-point combinations of buildings? What are the most favorable rows of buildings in each layout? etc.

Finally, among the limitations it should also be included or reported that the implications of designing wind environments for the buildings of Shenyang refer only to the current state of affairs. They do not investigate or propose anything about the implications of other possible locations, shapes and heights of buildings.

Last remark: should be added in paragraph 2.3 and paragraph 3.2 that “more and more high-rise buildings are designed for economic reasons and also to save construction land”.

Author Response

Dear editors and reviewers:

 

Thank you very much for your letter, and the referees’ reports. Based on your comment and request, we have made extensive modification on the original manuscript. A document answering every question from the referees was also summarized and enclosed.

If you have any questions, please contact us without hesitation.

 

Reviewer 2：

The theme and approach presented in the paper are not innovative (and not even recent) - the need has in fact been known since the time of Vitruvius: … “Streets or public ways ought therefore to be so set out, that when the winds blow hard their violence may be broken against the angles of the different divisions of the city, and thus dissipated” (cfr.de Architectura, Book VI).

Despite this and also thanks to the evolution over time of the tools for simulations (see fluent), the paper - which analyzes a specific case - to be concretely具体地 useful should have as main objective to turn to the authorities of the construction departments of Shenyang and only afterwards to turn to designers and urban planners.

With this in mind, the text should be much more concise in the references on the state of the art, eliminate some repetitions, but above all present the results of the simulations in tables (such as in Table 1 The building arrangements for the simulation), or graphic diagrams. In this way the results would be easy and immediate to read.

The results presented in the current discursive way do not allow to have an overall picture of the potential and criticality of each of the 12 kinds of layouts analyzed: which layouts and with which types of buildings are the most critical in winter / summer? What are the most favorable slab-point combinations of buildings? What are the most favorable rows of buildings in each layout? etc.

Finally, among the limitations it should also be included or reported that the implications of designing wind environments for the buildings of Shenyang refer only to the current state of affairs. They do not investigate or propose anything about the implications of other possible locations, shapes and heights of buildings.

Last remark: should be added in paragraph 2.3 and paragraph 3.2 that “more and more high-rise buildings are designed for economic reasons and also to save construction land”.

 

Answers to reviewer 2:

Thank you very much for referees’ reports. I seriously pondered the expression of the results in the article and found that there were indeed questions raised by the reviewer. We eliminated some repetitions and present the results of the simulations in tables.

After analyzed 12 kinds of layouts, we make the summary in Table 5 and mark the recommended layouts, which could be easy to read. The slab buildings(B), point buildings(D), combination of slab and point buildings (A) and (C) are the most favorable layouts in winter. In this paper, we focus more on the whole wind environment of different residential layouts, the wind environment of buildings on the south would be better than that on the north in Shenyang area in winter.

Finally, we proposed the implications of other possible locations. The different shapes and heights of buildings would be investigated in the future study.

We have added in paragraph 2.3 and paragraph 3.2 that “more and more high-rise buildings are designed for economic reasons and also to save construction land”.

 

Original:

 

We illustrated the results of 12 kinds of layouts in a discursive way. After that we eliminated some repetitions and present the results of the simulations in tables.

 

Amendment:

Table 2. The simulation results of slab buildings

 

Table 3. The simulation results of point buildings

 

Table 4. The simulation results of slab-point combination buildings.

 

Among the 12 kinds of layouts, SB(B), PB(D), CB(A), CB(C) can ensure favorable wind environments in the case of strong cold wind in winter in Shenyang area (Table 5.). These layouts may also be suitable for cold areas such as Tieling and Anshan, whose weather conditions are similar to those of Shenyang.

 

Table 5. overall results of the 12 kinds of layouts

 

2.3 Wind environment studies in China

With the acceleration of urbanization in China, more and more high-rise buildings are designed for economic reasons and also to save construction land.

3.2 Methods

Nowadays, the construction departments of Shenyang encourage the construction of high-rise buildings in the city center for economic reasons and also to save construction land.

Author Response File: Author Response.docx

Reviewer 3 Report

The merit of the study is good and needed. However, the hypothetical scenarios are very weak.

In urban and architectural design, the orientation is critical, and the conclusion from such a study should be realistic as possible. Giving a conclusion based on the current situation cannot be generalised as the distribution of the buildings and orientation could change the outcomes.

I suggest that the authors link the study for a specific location with specific urban planning outlines and buildings dimensions based on the city's policies. In this case, the study could be valid, and the city could benefit from this investigation as the wind study is location specific and could not be generalised.

Also, you need to explain for the readers based on what you added point buildings and slab-point terminologies. Maybe reference?

In addition, Does the regulation allow only 60 m high there? What is the current situation?

 

Author Response

Dear editors and reviewers:

 

Thank you very much for your letter, and the referees’ reports. Based on your comment and request, we have made extensive modification on the original manuscript. A document answering every question from the referees was also summarized and enclosed.

If you have any questions, please contact us without hesitation.

Reviewer 3：

The merit of the study is good and needed. However, the hypothetical scenarios are very weak.

In urban and architectural design, the orientation is critical, and the conclusion from such a study should be realistic as possible. Giving a conclusion based on the current situation cannot be generalised as the distribution of the buildings and orientation could change the outcomes.

I suggest that the authors link the study for a specific location with specific urban planning outlines and buildings dimensions based on the city's policies. In this case, the study could be valid, and the city could benefit from this investigation as the wind study is location specific and could not be generalised.

Also, you need to explain for the readers based on what you added point buildings and slab-point terminologies. Maybe reference?

In addition, Does the regulation allow only 60 m high there? What is the current situation?

Answers to reviewer 3:

Thank you very much for referees’ reports. I seriously pondered the expression of the paper and found that there were indeed questions raised by the reviewer. We have added the explanation of Shenyang’s construction policies, and the simulated buildings’ orientation is based on the policies. According to the suggestion, the point buildings, slab buildings and slab-point terminologies are illustrated and explained clearly in the paper. In addition, why we choose 60 meters as the height of simulated buildings was explained in the paper.

Add:

The Design standard for energy efficiency of residential buildings in severe cold and cold zones propose that the buildings orientation should be north-south or close to north-south [39]. In the cold areas of China, the orientation of residential buildings in the whole city is relatively fixed, and most of them are in the north-south orientation, which can also be seen from the survey results (Figure 2). Therefore, we defined the simulated buildings as the north-south orientation. The Uniform Standard for design of civil buildings defined that the height of high-rise residential buildings is between 27 meters and 100 meters [40]. The Code for fire protection design of buildings divide the high-rise buildings into two categories, one is 54 to 100 meters, and the other is 27 to 54 meters [41]. The former requires higher fire protection than the latter, and some building developers will limit the height of the building to 54 meters. Together with parapet and other decoration components, the total height of the building is about 60 meters.

 

Figure 2. Some high-rise residential areas in Shenyang (Data source: Drawn by author).

Slab buildings and point buildings are two common forms of high-rise buildings in China [42]. It can be seen from Figure 2 that there are three kinds of residential areas in Shenyang, the first one is composed by slab buildings, the second is composed by point buildings, and the third is composed by both slab buildings and point buildings. It can be seen from Figure 3 that the length of a slab building is far greater than its width and that a slab building looks like a slab in a general plan. However, for point buildings, the length and width are the same. Also, a point building looks like a square point in a general plan. Each flat in the slab building has a larger building area while the point building is smaller. These two architectural forms are more common in Chinese cities in order to meet the needs of different households. By analyzing and comparing the wind velocity ratio, wind velocity vector map, and wind pressure at the pedestrian level, the relationship between the wind environment and plane layouts could be obtained. In addition, a wind pressure diagram was used to analyze the heat preservation of the building envelopes, providing references and evaluation bases for planning the layouts of the residential areas in Shenyang.

Figure 3. Slab buildings and Point buildings (Data source: Drawn by author)

39.JGJ 26-2018, Design standard for energy efficiency of residential buildings in severe cold and cold zones[s].

40.GB50352-2019, Uniform Standard for design of civil buildings[s].

41.GB50016-2014, Code for fire protection design of buildings[s].

42.H, Chen, Numerical Simulation Analysis of Outdoor Wind Environment of Two Kinds of Buildings[J]. Refrigeration, 2020, 39 (04):30-33.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Good luck

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

This paper investigates how different building layouts may affect the pedestrian-level wind conditions in Shenyang, China, and provides suggestions for residential planning. More work still need to be done to improve the study and the manuscript.

 

1. The Introduction section seems a bit too long to get to the main objective of this study. I suggest that the authors put the extensive literature review in a new section right after the Introduction. For the Introduction section, the authors can summarize the existing studies and discuss the gaps to inform readers why this study should be done.

2. The novelty and contribution of this study are not well stated. As has been mentioned in the lit review, there are a few studies using CFD simulation to investigate the pedestrian-level wind conditions in cold regions of China (e.g., ref [31]). How does this study advance knowledge compared to existing studies? A possible way to think of it: the authors claim that one limitation of existing studies is that they are “not combined with the actual situation”, but more discussions should be included in terms of what “actual situation” means in this context (e.g., existing studies missed some important factors that may affect wind conditions, but you take them into consideration).

3. Figure 1: What is the data source? It should be indicated in the caption.

4. Section 2.2: With the aim of reproducibility, the authors should provide access to the CFD software and GAMBIT pre-processing software (via a link in the footnote or a reference).

5. Section 2.2.1: “according to the size selection method of calculation domain” should talk more about the method or at least add some references here. Same for other methods (e.g., standard κ -ε model) mentioned in the manuscript without any references.

6. Section 2.2.4: The building arrangement in Shenyang is essential to the simulation. However, more discussions should be included about it. For example, what are slab buildings and point buildings (I know there are some diagrams in Table 2, but definitions should be given as well)? How are these two types of buildings combined to form a certain layout (any references)?

7. The manuscript needs to be proofread by the authors. There are many spellings, grammatical, and formatting issues that need to be addressed. I have listed some of them below.

(1) Title: “residential area” to “residential areas”

(2) Line 9, Page 2: “…, on the other hand, …” to “…; on the other hand, …”

(3) Line 4, Page 3: “The published paper containas a vast number of papers…” not clear what this means

(4) Some sentences are too long to read (e.g., Section 2.2.1: “In order to… domain”).  

Author Response

Point 1: The Introduction section seems a bit too long to get to the main objective of this study. I suggest that the authors put the extensive literature review in a new section right after the Introduction. For the Introduction section, the authors can summarize the existing studies and discuss the gaps to inform readers why this study should be done.

 

Response 1: Thank you very much for referees’ reports. I seriously pondered the issue of the Introduction section, and felt that there was a problem with the previous writing method. Therefore, the full text was carefully modified. The revision consists of two parts, which are the Introduction (marked as①) and Literature review (marked as②). After summarizing the previous research on urban wind environments in residential areas, we find that due to the restriction of economic factors, more and more high-rise residential areas have been built in China. At present, there is a lack of simulation and comparison of wind environment in different planning modes of high-rise residential areas in severe cold regions in China. Besides, some of the current wind environment research are mainly at macroscopic view and ignored to adhere to the government standard and codes. This study can provide guidance for the plan of residential areas in Shenyang by simulating different kinds of architecture layouts.  That is why the study of wind environment of residential areas in Shenyang should be done.

 

 

Original: In Chinese mega cities, residential areas are one of the most important activity spaces in urban areas. Outdoor ventilation of residential area is an essential part of urban microclimate studies [1]. At present, the residential areas in many big cities in China are composed of high-rise buildings, which will lead to excessive instantaneous wind speed in some areas. However, High wind speed at pedestrian level can lead to uncomfortable or even dangerous conditions [2-6]. Lawson and Penwarden (1975) has reported the death of two old ladies due to an unfortunate fall caused by high wind velocity at the base of a tall building [7]. Therefore, many government agencies are studying new policies to improve the comfort and safety of wind condition around buildings. A moderate wind environment can not only improve human comfort, but also facilitate the diffusion process of pollutants , contribute to energy conservation and decrease urban heat island [2, 8-11]. Many urban planners have made it is necessary to discuss the pedestrian level wind condition for large urban communities at initial design stage [12-14]. Therefore, it is quite important to evaluate the wind comfort at pedestrian level and obtain an acceptable wind environment from urban planning development perspective.

Scholars from all over the world have considered the shape and space of buildings layout, building orientation, street canyon and many other influencing factors in the wind environment of pedestrian level around the building. A great deal of research has been done, which provides valuable reference for follow-up research. In the initial design stage of Tel Aviv's new business district, Israeli architect Cape Lutois Sac G took sunshine, wind direction, wind speed and other climatic factors into account, and proposed a new design process to reduce the impact of sunshine on building groups, urban roads and business districts [15]. The advantage of the project is that on the one hand, it can provide the business district with a suitable wind environment, on the other hand, it can also meet the residents' requirements in living areas. Tsang et al. used wind tunnel test method to evaluate the wind environment at outdoor pedestrian height of high-rise buildings from three aspects: architectural geometric factors, spacing and podium [16-17]. The research shows that the increase of the height of a single building is conducive to the natural circulation of airflow at pedestrian height, but the increase of width will expand the area of low wind speed zone. When the building width is more than twice the spacing, the increase of building height will affect the natural ventilation and adversely affect the outdoor wind environment. In addition, the podium is unfavorable to the building area which needs natural ventilation. Jonas A et al. analysed the microclimate by studying six different urban topologies, with only the building heights of the individual buildings are changed [18]. The results show that the change of building height will have an obvious impact on the surrounding microclimate, and the temperature change around the building is related to the surrounding air flow and heat diffusion efficiency. T. Stathopoulos indicated that circular and polygon shaped building corner contribute to better wind climate comparing with the square-shaped corner due to reduced downwash [19]. Some other professors concentrated on the wind condition when buildings and the wind direction in different angles, and indicated that the windage resistance of small angles is weak, which will result in higher wind velocity [20-21].

In urban design, different spatial morphology not only affect traffic, but also form different microclimates. Appropriate arrangements of buildings can facilitate comfortable wind environment for pedestrians. M Rohinton Emmanuel focused on climate-sensitive design in tropical areas, and put forward the method of improving urban climate and reducing energy consumption through urban design, and made analysis on how to use architectural layout design to reduce the impact of urban heat island effect, promote the improvement of microclimate around buildings, and make contribution to urban environment, which provided theoretical basis for related research in other different climate regions [22]. Gordon B. Bonan et al. studied the relationship between the density of residential buildings and the wind environment through satellite images on GIS, and concluded that the wind environment in residential areas would be affected by the density of residential buildings and the wind speed in urban areas with high building density would be lower [23-24]. Besides, Kubota et al., Taleghani et al. and Mehdi Shahrestani et al. conducted pedestrian-level wind condition analysis of several typical residential layout modes in Japan, the Netherlands and UK [25-27]. Building arrangements which provided optimal wind environment for each area were proposed in these studies.

With the acceleration of urbanization in China, more and more high-rise buildings are designed for saving construction land. At the same time, urban residents put forward higher requirements for comfortable and safe environment, and the outdoor wind environment in residential areas has gradually attracted the attention of experts. Zhang et al. conducted both CFD simulation and wind tunnel study to explore wind conditions around different building layout, and found that the staggered arrangement facilitate more wind into the site, which can improve natural ventilation in residential area [28]. Some experts in Nanjing and Chongqing pointed out that scattered points layout is helpful for the ventilation due to the less site coverage [29-30]. Shui et al. carried out experiment of the wind condition of 7 residential areas and found that multi-storey residential areas with hybrid-type and the enclosed-type layout are suitable in severe cold regions in China [31]. The published paper containas a vast number of papers on perdestrain level wind environment of residential areas. However, these papers show inconsistent results of different residential layout modes. This is due to these studies were conducted in different thermal zone in China and some of the simulation samples are not combined with the actual situation.

There are three main types of residential area plans in China: determinant layout, enclosing layout and mixed layout. Residential areas generally cover a large area and have a regular layout. According to the planning characteristics of spatial morphology of residential areas in China, the government published some evalution standard and planning restrictions. Design standard for thermal environment of urban residential areas suggests that in I, II, In Ⅲ and Ⅳ building climate zones, residential areas with high building density should be arranged in the upwind direction of the dominant wind direction in winter, in Ⅲ, Ⅳ, Ⅴbuilding climate zones, residential areas with high building density are arranged in the downwind of the dominant wind direction in summer [32]. The assessment standard for green building suggests that in winter, the wind speed and the wind velocity ratio at perdestrain level should lower than 5m/s and 2, and the wind pressure difference between windward side and leeward side of the building is less than 5 Pa, which can reduce the penetration of cold air into the room. In summer, there should be no windless zone in residential quarters, which will affect the heat dissipation of buildings and the dissipation of pollutants. The difference of wind pressure between the inner and outer surfaces of windows should be higher than 0.5 Pa, which will be beneficial to natural ventilation [33]. However, some of the current wind environment research ignored to adhere to the government standard and codes.

In this paper, the layout mode of residential areas which facilitates favorable wind environment in Shenyang is proposed through Computational Fluid Dynamics (CFD) simulation. Firstly, the typical patterns of residential district layout in Shenyang are investigated and summarized, by which the simulation samples are selected. Then, the wind environment of residential district is simulated according to the climatic conditions in Shenyang, and the simulation results are analyzed using Chinese green building evaluation standards. Finally, the architectural layout which is suitable for the climate conditions of Shenyang is put forward. This study will provide more choices for architectural layout in cold regions of China, and will also provide practical suggestions for residential district planning.

Amendment:

• Introduction

In Chinese mega cities, a residential area is one of the most important activity spaces in urban areas. Outdoor ventilation of residential areas is an essential part of urban microclimate studies [1]. At present, the residential areas in many big cities in China are composed of high-rise buildings, which will lead to excessive instantaneous wind speed in some areas. However, High wind speed at pedestrian level can lead to uncomfortable or even dangerous conditions [2-6]. Lawson and Penwarden (1975) has reported the death of two old ladies due to an unfortunate fall caused by high wind velocity at the base of a tall building [7]. Therefore, many government agencies are studying new policies to improve the comfort and safety of wind condition around buildings. A moderate wind environment can not only improve human comfort, but also facilitate the diffusion process of pollutants , contribute to energy conservation and decrease urban heat island [2, 8-14]. Many urban planners have made it is necessary to discuss the pedestrian level wind condition for large urban communities at initial design stage [15-17]. Therefore, it is quite important to evaluate the wind comfort at pedestrian level and obtain an acceptable wind environment from urban planning development perspective.

Shenyang locates in the northeast of China, where the winter is long and severe cold. And it is described as severe cold region in the Code for thermal design of civil building GB 50176-2016 [18]. In winter, strong wind contributes to the the degree of discomfort, espically in severe cold areas. Therefore, it is essential to obtain an adorable wind environment in severe cold regions from the human confort perspective. Liu et al. investigated the prediction model of pedestrian-level wind chill temperature of Chinese high-rise residential areas, and proposed the pedestrain level thermal sensation evaluation of six major cities in Chinese severe cold regions [19]. Jin et al. studied the influence factors of thermal comfort of pedestrain street in severe cold regions of China and suggested that the optimization in winter focuses on blocking the wind [20]. Yang et al. took 31 cities in China as examples to investigate the relationship between urban ventilation and the energy demand from a thermal environment perspective and indicated that good ventilation could reduce the energy demand in the summer and increases the energy demand in the winter [21]. These studies mainly focused on the contribution of urban ventilation on the thermal environment and considered that it is important to control the pedestrain level wind environment of residential areas in severe cold regions in China.

There are three main types of residential plans in China: determinant layout, enclosing layout and mixed layout. Residential areas generally cover a large area and have a regular layout. Shui conducted questionnaire survey of human wind comfort in 7 typical residential areas and suggested that the enclosing layout and the mixed layout are suitable for the multi-storey residential areas in severe cold regions [22]. Although several studies about wind conditions at pedestrain level in cold regions of China have been explored in prior work, the most studies focused on some certain residential areas, the classification of residential areas need to be more comprehensive. It takes time to simulate the wind environment of each residential area in the early stage of design. one good solution is to simplify the current residential layouts into several typical ones for wind environment assessment, which is convenient for architects to choose a suitable layout for in-depth design.

Considering the current trend that more and more high-rise residential areas are built in Shenyang, 12 typical layouts of newly-built high-rise buildings are summarised in this study and the wind environment of each layout is assessed. In this paper, the layout mode of residential areas which facilitates favorable wind environment in Shenyang is proposed through Computational Fluid Dynamics (CFD) simulation. Firstly, the typical patterns of residential district layout in Shenyang are investigated and summarized, by which the simulation samples are selected. Then, the wind environment of residential district is simulated according to the climatic conditions in Shenyang, and the simulation results are analyzed using Chinese green building evaluation standards. Finally, the architectural layout which is suitable for the climate conditions of Shenyang is put forward. This study will provide more choices for architectural layouts in cold regions of China, and will also provide practical suggestions for urban residential planning.

②Literature Review

2.1 Effect of architectural geometric factors

Scholars from all over the world have considered the shape and space of buildings layouts, building orientation, street canyon and many other influencing factors in the wind environment of pedestrian level around the building. A great deal of research have been done, which provides valuable reference for follow-up research. In the initial design stage of Tel Aviv's new business district, Israeli architect Cape Lutois Sac G took sunshine, wind direction, wind speed and other climatic factors into account, and proposed a new design process to reduce the impact of sunshine on building groups, urban roads and business districts [23]. This project can provide the business district with a suitable wind environment, and can also meet the residents' requirements in living areas. Jonas A et al. analysed the microclimate by studying six different urban topologies, with only the building heights of the individual buildings are changed [24]. The results show that the change of building height will have an obvious impact on the surrounding microclimate, and the temperature change around the building is related to the surrounding air flow and heat diffusion efficiency. T. Stathopoulos indicated that circular and polygon shaped building corner contribute to better wind climate comparing with the square-shaped corner due to reduced downwash [25]. Some other professors concentrated on the wind condition when buildings and the wind direction in different angles, and indicated that the windage resistance of small angles is weak, which will result in higher wind velocity [26-27].

2.2 Effect of architectural spatial morphology

In urban design, different spatial morphology not only affect traffic, but also form different microclimates. Appropriate arrangements of buildings can facilitate comfortable wind environment for pedestrians. M Rohinton Emmanuel focused on climate-sensitive design in tropical areas, and put forward the method of improving urban climate and reducing energy consumption through urban design, and made analysis on how to use architectural layout design to reduce the impact of urban heat island effect, promote the improvement of microclimate around buildings, and make contribution to urban environment, which provided theoretical basis for related research in other different climate regions [28]. Gordon B. Bonan et al. studied the relationship between the density of residential buildings and the wind environment through satellite images on GIS, and concluded that the wind environment in residential areas would be affected by the density of residential buildings and the wind speed in urban areas with high building density would be lower [29-30]. Besides, Kubota et al., Taleghani et al. and Mehdi Shahrestani et al. conducted pedestrian-level wind condition analysis of several typical residential layout modes in Japan, the Netherlands and UK [31-33]. Building arrangements which provided optimal wind environment for each area were proposed in these studies.

2.3 Wind environment studies in China

With the acceleration of urbanization in China, more and more high-rise buildings are designed for saving construction land. At the same time, urban residents put forward higher requirements for comfortable and safe environment, and the outdoor wind environment in residential areas has gradually attracted the attention of experts. Zhang et al. conducted both CFD simulation and wind tunnel study to explore wind conditions around different building layout, and found that the staggered arrangement facilitate more wind into the site, which can improve natural ventilation in residential areas [34]. Some experts in Nanjing and Chongqing pointed out that scattered points layout is helpful for the ventilation due to the less site coverage [35-36]. Shui et al. carried out experiment of the wind condition of 7 residential areas and found that multi-storey residential areas with hybrid-type and the enclosed-type layout are suitable in severe cold regions in China [22]. The published paper containas a vast number of papers on perdestrain level wind environment of residential areas. However, more studies were conducted in southern China.

2.4 Codes and standards in China

According to the planning characteristics of spatial morphology of residential areas in China, the government published some evalution standard and planning restrictions. Design standard for thermal environment of urban residential areas suggests that in I, II, In Ⅲ and Ⅳ building climate zones, residential areas with high building density should be arranged in the upwind direction of the dominant wind direction in winter, in Ⅲ, Ⅳ, Ⅴbuilding climate zones, residential areas with high building density are arranged in the downwind of the dominant wind direction in summer [37]. The assessment standard for green building suggests that in winter, the wind speed and the wind velocity ratio at perdestrain level should lower than 5m/s and 2, and the wind pressure difference between windward side and leeward side of the building is less than 5 Pa, which can reduce the penetration of cold air into the room. In summer, there should be no windless zone in residential quarters, which will affect the heat dissipation of buildings and the dissipation of pollutants. The difference of wind pressure between the inner and outer surfaces of windows should be higher than 0.5 Pa, which will be beneficial to natural ventilation [38].

The shortcomings in previous research on urban wind environments in residential areas can be summarized as follows:

• Due to the restriction of economic factors, more and more high-rise residential areas have been built in China. At present, there is a lack of simulation and comparison of wind environment in different planning modes of high-rise residential areas in severe cold regions in China.
• Some of the current wind environment research are mainly at a macroscopic view and ignored to adhere to the government standard and codes.  

This paper summarizes the high-rise residential quarters in Shenyang more comprehensively and simplifies them into a more intuitive model. Through numerical simulation, residential layouts with favourable pedestrian-level wind conditions were obtained for Shenyang's climate condition. The research results can directly guide architectural design from the perspective of urban wind environment.

Point 2: The novelty and contribution of this study are not well stated. As has been mentioned in the lit review, there are a few studies using CFD simulation to investigate the pedestrian-level wind conditions in cold regions of China (e.g., ref [31]). How does this study advance knowledge compared to existing studies? A possible way to think of it: the authors claim that one limitation of existing studies is that they are “not combined with the actual situation”, but more discussions should be included in terms of what “actual situation” means in this context (e.g., existing studies missed some important factors that may affect wind conditions, but you take them into consideration).

Response 2: Thank you very much for referees’ reports. There are a few studies using CFD simulation to investigate the pedestrian-level wind conditions in cold regions of China, however, most of the studies focused on multistorey buildings. The “actual situation” is that government encourage the construction of high rise buildings for saving land, therefore, the wind environment of high rise residential areas should be evaluated. In this study, we propose 12 typical combination forms from the investigation of more than 50 residential areas and put forward the wind environment accessment of them. After that, we analyse the wind environment of them using Assessment standard for green building of China, which  is rarely mentioned in previous studies. We add some explanation of contribution in Literature review section and investigation pictures in 3.2 Methods (Figure 2).

 

Amendment:

The shortcomings in previous research on urban wind environments in residential areas can be summarized as follows:

• Due to the restriction of economic factors, more and more high-rise residential areas have been built in China. At present, there is a lack of simulation and comparison of wind environment in different planning modes of high-rise residential areas in severe cold regions in China.
• Some of the current wind environment research are mainly at a macroscopic view and ignored to adhere to the government standard and codes.  

This paper summarizes the high-rise residential quarters in Shenyang more comprehensively and simplifies them into a more intuitive model. Through numerical simulation, residential layouts with favourable pedestrian-level wind conditions were obtained for Shenyang's climate condition. The research results can directly guide architectural design from the perspective of urban wind environment.

Figure 2: Some high rise residential areas in Shenyang (Data source: Drawn by author)

 

 

 

 

 

Point 3: Figure 1: What is the data source? It should be indicated in the caption.

 

Response 3: Thank you very much for referees’ reports. We have changed Figure 1 with a clear picture and added the reference of it in the caption.

 

Original:

 

Figure 1. Wind rose of Shenyang.

Amendment:

 

Figure 1. Wind rose of Shenyang. (Data source: Architectural Design Data Set of China.［M］.Beijing. 2017)

 

 

 

 

 

Point 4:  Section 2.2: With the aim of reproducibility, the authors should provide access to the CFD software and GAMBIT pre-processing software (via a link in the footnote or a reference).

 

Response 4: Thank you very much for referees’ reports. We have added the references of  the CFD software and GAMBIT pre-processing software in the manuscript. Besides, we have modified the Material and Method section and made it easier to read.

 

Original:

2. Materials and Methods

2.1. Study Area

Shenyang is the capital of Liaoning Province, the economic, cultural, transportation, financial and commercial center of Northeast China, and also an important industrial base and historical and cultural city in China. It is located in the south of Northeast China (42°21’N, 123°28’ E), with a continental monsoon climate in North temperate zone, cold in winter and warm in summer. The cold period is long, spring and autumn are short and windy. The temperature difference in four seasons is obvious in Shenyang. The annual mean temperature and humidity is 8.1℃, and 63% respectively. Figure 1 is the wind rose map of Shenyang, from which we can see that he wind direction is relatively stable all year round, and the maximum wind direction is mainly from south in summer and north in winter.

 

Figure 1. Wind rose of Shenyang.

Due to the special climatic conditions, the buildings in Shenyang have the following characteristics: Traditional dwellings are thick and closed, usually the thickness of the external wall is more than 370mm. The courtyard is open, and the buildings only open windows to the courtyard, so as to effectively prevent the invasion of cold wind in winter. At present, The thickness of modern building block wall and insulation is generally 200mm to 300mm, and 50 mm to 80 mm, respectively. The building shape coefficient is relatively small to reduce the heat dissipation area, and the winter heat preservation requirements are mainly considered in the building design process.

 

2.2. Methods

In this paper, CFD fluent software is used to simulate the building wind environment formed by different architectural layout, which include slab buildings arrangement, point buildings arrangement and slab-point combination buildings arrangement. By analyzing and comparing the wind velocity ratio, wind velocity vector map and wind pressure at pedestrian height, the relationship between the wind environment and the plane layout can be obtained. In addition, the wind pressure diagram is used to analyze the heat preservation of building envelope, which provides reference and evaluation basis for the planning and layout of residential areas in Shenyang. Combining with the actual situation in Shenyang, this study takes winter as the main evaluation season. According to the Architectural Design Data Set of China, the dominant wind direction in winter is north , and the average wind velocity is 3.0m/s.

2.2.1. Selection of calculation model

In order to prevent the treatment of each outflow boundary condition from affecting the actual flow field distribution around the building, and at the same time ensure that the inflow surface is not affected by the building, so that the influence of the building on the flow around in this area is completely eliminated at the boundary, and finally ensure that the inflow and outflow control bodies realize mass conservation, a larger simulation space should be adopted in the calculation domain. In this way, the two-dimensional flow field is selected for simulation, and the buildings are placed in the range of X×Y =360×500(m) according to the size selection method of calculation domain.

2.2.2. Model selection and grid division

The outdoor airflow at the bottom of the atmosphere is generally in the range of low-speed flow, and the air can be assumed as Boussinesq, which is a viscous and incompressible fluid. The standard κ -ε model is selected to simulate the wind environment of buildings. GAMBIT pre-processing software of FLUENT is used for grid division. Line grids and area grids are divided for buildings and peripheral large-scale computational domains, dense grids are arranged near solid areas, and sparse grids are adopted in areas far away from the model, and all grids are triangles.

2.2.3. Reference pressure position setting

A reference pressure position should be set due to incompressible flow. Regardless of the gravity influence, operating pressure is set to the standard atmospheric pressure of 101325Pa.

2.2.4. Selection of boundary conditions

Velocity inlet is selected as the entrance boundary condition, and the velocity value is 3m/s, which is the dominant wind velocity in winter. Outlet boundary condition is selected as outflow, which is suitable for the case where the pressure or velocity on the outlet boundary is unknown.

According to the actual typical buildings layout condition in Shrenyang, slab buildings and point buildings are selected as simulation samples. The two kinds of buildingsare simplified into regular quadrangles before simulation, and the sizes of point buildings and slab buildings are respectively 20m×20m×60m (length×width×height) and 45m×15m×60m. The specific arrangement is shown in Table 1.

Table 2. The building arrangements for simulation

2.2.5. Evaluation standard of wind velocity ratio

In practical application, wind velocity ratio (wind speed amplification) is used as comfort parameter to discuss the comfort of wind environment around buildings. Wind velocity ratio reflects the degree of wind velocity change caused by the existence of buildings. Wind velocity ratio Ri is defined as:

Ri=Vi／Vo

Where Ri is the ratio of wind velocity at the position of i point (dimensionless), Vi is Average wind velocity at pedestrian height at point i in the flow field, Vo is average wind velocity of undisturbed incoming flow at pedestrian height, generally the initial wind velocity.

Wind velocity ratio evaluation is a common evaluation standard of wind comfort. This study will use this index to discuss the outdoor wind environment comfort of Shenyang residential area under different arrangement forms.

 

Amendment:

3. Materials and Methods

3.1. Study Area

Shenyang is the capital of Liaoning Province, the economic, cultural, transportation, financial and commercial center of Northeast China, and also an important industrial base and historical and cultural city in China. It is located in the south of Northeast China (42°21’N, 123°28’ E), with a continental monsoon climate in North temperate zone, cold in winter and warm in summer. The cold period is long, spring and autumn are short and windy. The temperature difference in four seasons is obvious in Shenyang. The annual mean temperature and humidity is 8.1℃, and 63% respectively. Figure 1 is the wind rose map of Shenyang, from which we can see that the wind direction is relatively stable all year round, and the maximum wind direction is mainly from south in summer and north in winter.

Due to the special climatic conditions, the buildings in Shenyang have the following characteristics: Traditional dwellings are thick and closed, usually the thickness of the external wall is more than 370mm. The courtyard is open, and the buildings only open windows to the courtyard, so as to effectively prevent the invasion of cold wind in winter. At present, The thickness of modern building block wall and insulation is generally 200mm to 300mm, and 50 mm to 80 mm, respectively. The building shape coefficient is relatively small to reduce the heat dissipation area, and the winter heat preservation requirements are mainly considered in the building design process.

Figure 1. Wind rose of Shenyang.(Data source: Architectural Design Data Set of China.［M］.Beijing. 2017)

 

3.2. Methods

In this paper, CFD fluent software [44] is used to simulate the building wind environment formed by different architectural layouts. Through the investigation of more than 50 residential areas in Shenyang, it is found that the newly-built residential areas in Shenyang are mainly composed of slab buildings , point buildings amd slab-point combination buildings (Figure 2). 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 2: Some high rise residential areas in Shenyang (Data source: Drawn by author)

 

Slab buildings and point buildings are two common forms of high-rise buildings in Shenyang. It can be seen from the Figure 3 that the slab building is that the length of the building is far greater than the width and looks like a piece of slab in general plan, while the point building is that the length and width of the building are similar in size and it looks like a square point in general plan. By analyzing and comparing the wind velocity ratio, wind velocity vector map and wind pressure at pedestrian height, the relationship between the wind environment and the plane layouts can be obtained. In addition, the wind pressure diagram is used to analyze the heat preservation of building envelope, which provides reference and evaluation basis for the planning and layout of residential areas in Shenyang.

 Figure 3: Slab buildings and Point buildings (Data source: Drawn by author)

Nowdays, the construction departments of Shenyang encourage the construction of high-rise buildings in the city center for saving construction land. However, More and more high-rise buildings may cause complex wind environment, and in winter when the temperature is low, the high wind speed in the residential areas may cause discomfort to pedestrians. In consideration of this situation in Shenyang, this study takes winter as the main evaluation season. According to the Architectural Design Data Set of China [39], the dominant wind direction in winter is north , and the average wind velocity is 3.0m/s.

3.2.1. Computational domain and grids

The size of calculation area will directly affect the accuracy of simulation. If the calculation area is small, the flow field will be distorted. A large calculation area will result in many grids and increase the calculation amount and cost. According to relevant experience at home and abroad, the simulation area is set at 360m×500m, and the calculation height is 5 times of the building height [22, 40-41].  The outdoor airflow at the bottom of the atmosphere is generally in the range of low-speed flow, and the air can be assumed as Boussinesq, which is a viscous and incompressible fluid. Generally, CFD software is equipped with various turbulence models, and k-ε model is the most widely used one for engineering applications. It has low calculation cost, small fluctuation and high precision in numerical calculation [42]. DB11 /938-2012 Standard for Green Building Design (Beijing) suggests that the standard k-ε model can be used when the calculation accuracy is not high and only the flow field at a height of 1. 5 m is concerned [43]. Therefore, the standard k-ε model is selected in this study to simulate the wind environment of buildings. GAMBIT pre-processing software [44] of FLUENT is used for grid division. Line grids and area grids are divided for buildings and peripheral large-scale computational domains, dense grids are arranged near solid areas, and sparse grids are adopted in areas far away from the model, and all grids are triangles. A reference pressure position should be set due to incompressible flow. Regardless of the gravity influence, operating pressure is set to the standard atmospheric pressure of 101325Pa.

3.2.2. Building arrangements for simulation

According to the typical buildings layouts condition in Shenyang, this study summerisd 12 kinds of layouts for numerial simulation . The two kinds of buildings are simplified into regular quadrangles before simulation, and the sizes of point buildings and slab buildings are respectively 20m×20m×60m (length×width×height) and 45m×15m×60m. The specific arrangement is shown in Table 1.

Table 1. The building arrangements for simulation

3.2.3. Evaluation standard of wind velocity ratio

In practical application, wind velocity ratio (wind speed amplification) is used as comfort parameter to discuss the comfort of wind environment around buildings [38]. Wind velocity ratio reflects the degree of wind velocity change caused by the existence of buildings. Wind velocity ratio Ri is defined as:

Ri=Vi／Vo

Where Ri is the ratio of wind velocity at the position of i point (dimensionless), Vi is Average wind velocity at pedestrian height at point i in the flow field, Vo is average wind velocity of undisturbed incoming flow at pedestrian height, generally the initial wind velocity.

Wind velocity ratio evaluation is a common evaluation standard of wind comfort. This study will use this index to discuss the outdoor wind environment comfort of Shenyang residential area under different arrangement forms.

 

Point 5: Section 2.2.1: “according to the size selection method of calculation domain” should talk more about the method or at least add some references here. Same for other methods (e.g., standard κ -ε model) mentioned in the manuscript without any references.

Response 5: Thank you very much for referees’ reports. We have modified the paper according to the review, and added some references.

Amendment:

The size of calculation area will directly affect the accuracy of simulation. If the calculation area is small, the flow field will be distorted. A large calculation area will result in many grids and increase the calculation amount and cost. According to relevant experience at home and abroad, the simulation area is set at 360m×500m, and the calculation height is 5 times of the building height [22, 40-41].  The outdoor airflow at the bottom of the atmosphere is generally in the range of low-speed flow, and the air can be assumed as Boussinesq, which is a viscous and incompressible fluid. Generally, CFD software is equipped with various turbulence models, and k-ε model is the most widely used one for engineering applications. It has low calculation cost, small fluctuation and high precision in numerical calculation [42]. DB11 /938-2012 Standard for Green Building Design (Beijing) suggests that the standard k-ε model can be used when the calculation accuracy is not high and only the flow field at a height of 1. 5 m is concerned [43]. Therefore, the standard k-ε model is selected in this study to simulate the wind environment of buildings.

Point 6: Section 2.2.4: The building arrangement in Shenyang is essential to the simulation. However, more discussions should be included about it. For example, what are slab buildings and point buildings (I know there are some diagrams in Table 2, but definitions should be given as well)? How are these two types of buildings combined to form a certain layout (any references)?

Response 6: Thank you very much for referees’ reports. We have modified the paper according to the review, and added some pictures in Materials and Method section to explain the slab buildings and point buildings. Figure 2 shows that there are some residential areas composed of slab buildings and point buildings. They have different combinations, such as point buildings on the north side and slab buildings on the south side, etc. In this paper, some forms are selected from the investigation for simulation research.

Amendment:

3.2. Methods

In this paper, CFD fluent software is used to simulate the building wind environment formed by different architectural layouts. Through the investigation of more than 50 residential areas in Shenyang, it is found that the newly-built residential areas in Shenyang are mainly composed of slab buildings , point buildings amd slab-point combination buildings (Figure 2). 

 

Figure 2: Some high rise residential areas in Shenyang (Data source: Drawn by author)

 

Slab buildings and point buildings are two common forms of high-rise buildings in Shenyang. It can be seen from the Figure 3 that the slab building is that the length of the building is far greater than the width and looks like a piece of slab in general plan, while the point building is that the length and width of the building are similar in size and it looks like a square point in general plan. By analyzing and comparing the wind velocity ratio, wind velocity vector map and wind pressure at pedestrian height, the relationship between the wind environment and the plane layouts can be obtained. In addition, the wind pressure diagram is used to analyze the heat preservation of building envelope, which provides reference and evaluation basis for the planning and layout of residential areas in Shenyang.

 Figure 3: Slab buildings and Point buildings (Data source: Drawn by author)

 

Point 7: The manuscript needs to be proofread by the authors. There are many spellings, grammatical, and formatting issues that need to be addressed. I have listed some of them below.

(1) Title: “residential area” to “residential areas”

(2) Line 9, Page 2: “…, on the other hand, …” to “…; on the other hand, …”

(3) Line 4, Page 3: “The published paper containas a vast number of papers…” not clear what this means

(4) Some sentences are too long to read (e.g., Section 2.2.1: “In order to… domain”).  

Response 7: Thank you very much for referees’ reports. We have modified the paper according to the review, and corrected the above mistakes.

Author Response File: Author Response.pdf

Reviewer 2 Report

The theme of the paper is irrelevant to Sustainability. It has no contribution to the concept of sustainability. 

Author Response

Point 1: The theme of the paper is irrelevant to Sustainability. It has no contribution to the concept of sustainability. 

Response 1: Thank you very much for referees’ reports. We consider that this paper has contribution to the concept of sustainability. Outdoor ventilation of residential areas is an essential part of urban microclimate studies. A moderate wind environment can not only improve human comfort, but also facilitate the diffusion process of pollutants , contribute to energy conservation and decrease urban heat island [1-7]. In this paper, we carry out neumerial simulation of the wind environment of different kinds of architecture layouts in cold region in China. This study could provide guidance to designers and urban planners about practical suggestions for residential planning.

 

1. Ai Z T, Mak C M. CFD simulation of flow in a long street canyon under a perpendicular wind direction: Evaluation of three computational settings[J]. Building and Environment, 2017, 114:293-306.
2. [1]Yang J ,  Yang Y ,  Sun D , et al. Influence of urban morphological characteristics on thermal environment[J]. Sustainable Cities and Society, 2021.
3. [1] Luo X ,  Yang J ,  Sun W , et al. Suitability of human settlements in mountainous areas from the perspective of ventilation: A case study of the main urban area of Chongqing[J]. Journal of Cleaner Production, 2021:127467.
4. [1] Yang J ,  Wang Y ,  Xiu C , et al. Optimizing local climate zones to mitigate urban heat island effect in human settlements[J]. Journal of Cleaner Production, 2020:123767.
5. Wu Y, Niu J. Numerical study of inter-building dispersion in residential environments: Prediction methods evaluation and infectious risk assessment[J]. Building & Environment, 2017, 115:199-214.
6. Yang X, Zhao L, Bruse M, et al. APPLICATION OF URBAN MICROCLIMATE SIMULATION DATA IN ASSESSING BUILDING ENERGY CONSUMPTION[J]. Acta Energiae Solaris Sinica, 2015, 36(6):1344-1351.
7. Hong B, Lin B, Lin J. Quantification of residential design parameters' effects on the outdoor wind environment using orthogonal experimental design (OED) and numerical simulation[J]. Procedia Engineering, 2017, 205:137-144.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Review of Pedestrian-level wind environment assessment of Shenyang's residential area by numerical simulation by Zhang & Zhang.

The authors use a CFD model to model the effect of various building formations on pedestrian wind fields for the city of Shenyang, China. While it is interesting to see the changes in (horizontal) wind fields caused by the various building morphologies, the paper doesn’t really answer any stringent scientific question: it’s more a commissioned report for the municipality of the city rather than an academic study. Furthermore, the Introduction mentions several causes of wind nuisance that are not addressed in the rest of the study (e.g. heat stress caused by null-winds) and the vertical dimension of wind, crucial in any real urban setup, is completely ignored. The connection to the literature feels poor, no physical background is given in the introduction, which itself does not connect well to the methodology, and results are presented at a very descriptive level, showing the numbers but not bothering to explain the causes behind them or coming up with a general framework.

I recommend to reject this paper: while the subject matter is interesting, it does not feel like an academic study worthy of publication in this journal. With more focus on theory and more thorough analysis, this could perhaps be achieved.

Below are some comments I’ve made during my read-through, perhaps they can be of help to the authors during this process:

 

 

• Intro: why does a concentration of high-rise buildings lead to more instantaneous high level wind speeds? Wind can often not penetrate down into the urban canyon, dependent on the street orientation versus wind direction.
• P2: Podium?
• General: way of citing researcher names is inconsistent and fairly irritating to read combined with the numbered citations. Try to reduce this or at least be consistent in using full names or surnames.
• The level of English is subpar, I recommend having the manuscript checked by a native speaker.
• Introduction is perhaps too long and could be made more condensed. Now the authors show quite a lot of examples of studies focusing on the built environment and its interaction with the wind, but the physical mechanisms are not discussed at all (why do different morphologies cause wind nuisance?). It’s good to show that the topic is relevant and being worked on, but the Introduction should also show some physical background, to lead up to the method used by the authors to research the causes and remedies. There’s no good connection between the Introduction and the method, and a research question is not clearly stated.
• 2.1: perhaps state the temperature differences, if they are that obvious.
• Fig 1: this almost looks like an old figure taken from a different study, given the low quality. Please cite the source if this is the case; if not, please increase image resolution. Additionally, expand the figure caption: there are two lines in the wind rose, which line represents which season?
• 2.2.: Winter is chosen as the evaluation period, but the introduction focuses on heat stress experienced in summer. Why not evaluate both?
• 2.2: too many subheaders, merge some.
• 2.1: perhaps include a schematic overview of the building layouts in the model. Include a reference to the FLUENT model?
• Table 2: there is no table 1, please re-number. Also, related to the previous point: this table nicely shows the building layouts, but it would be good to see them in the model domain.
• What is the vertical extent of the model? Is it high enough for correct boundary layer development and vertical downdrafts into street canyons?
• Figs 2-4: legends are hard to read, increase the sizes of those (and the figures themselves, it’s hard to see the vectors).
• Results: interesting to see the effect of these configurations side by side and how they impact the wind field. However, in a real city there is also a strong vertical component of the wind, especially when it hits a frontal surface and needs to go around it. This isn’t researched at all, even though it seems the most obvious one to me. While I can understand the limits of what can be put in a single paper, this at least bears some thorough discussion: why have you chosen to omit this part of the wind field?
• 4.2: what are “landscape sketches” and how will they help against wind nuisance? Have you tested any of these suggested implementations in the model?

Author Response

Point 1: Intro: why does a concentration of high-rise buildings lead to more instantaneous high level wind speeds? Wind can often not penetrate down into the urban canyon, dependent on the street orientation versus wind direction.

Response 1: Thank you very much for referees’ reports. Because of the urban gradient wind, the higher the building is, the higher the wind speed is. In this paper, “high-rise buildings lead to more instantaneous high level wind speeds” means that excessive wind speed around high-rise buildings will bring discomfort to people. That why the research about wind speed around high rise buildings is important.

Point 2:P2: Podium?

Response 2: Thank you very much for referees’ reports. We seriously pondered the issue of the Introduction section, and felt that there was a problem with the previous writing method. Podium refers to the affiliated building connected with the high-rise buildings. To avoid ambiguity, we deleted this improper reference in literature review section.

Point 3:General: way of citing researcher names is inconsistent and fairly irritating to read combined with the numbered citations. Try to reduce this or at least be consistent in using full names or surnames.

Response 3: Thank you very much for referees’ reports. We seriously pondered the issue of the Introduction section, and felt that there was a problem with the previous writing method. Therefore, the full text was carefully modified.

Point 4:The level of English is subpar, I recommend having the manuscript checked by a native speaker.Introduction is perhaps too long and could be made more condensed. Now the authors show quite a lot of examples of studies focusing on the built environment and its interaction with the wind, but the physical mechanisms are not discussed at all (why do different morphologies cause wind nuisance?). It’s good to show that the topic is relevant and being worked on, but the Introduction should also show some physical background, to lead up to the method used by the authors to research the causes and remedies. There’s no good connection between the Introduction and the method, and a research question is not clearly stated.

 

Response 4:Thank you very much for referees’ reports. I seriously pondered the expression of this section in the article and found that there were indeed questions raised by the reviewer. The revision consists of two parts, which are the Introduction (marked as①) and Literature review (marked as②). 

Original: In Chinese mega cities, residential areas are one of the most important activity spaces in urban areas. Outdoor ventilation of residential area is an essential part of urban microclimate studies [1]. At present, the residential areas in many big cities in China are composed of high-rise buildings, which will lead to excessive instantaneous wind speed in some areas. However, High wind speed at pedestrian level can lead to uncomfortable or even dangerous conditions [2-6]. Lawson and Penwarden (1975) has reported the death of two old ladies due to an unfortunate fall caused by high wind velocity at the base of a tall building [7]. Therefore, many government agencies are studying new policies to improve the comfort and safety of wind condition around buildings. A moderate wind environment can not only improve human comfort, but also facilitate the diffusion process of pollutants , contribute to energy conservation and decrease urban heat island [2, 8-11]. Many urban planners have made it is necessary to discuss the pedestrian level wind condition for large urban communities at initial design stage [12-14]. Therefore, it is quite important to evaluate the wind comfort at pedestrian level and obtain an acceptable wind environment from urban planning development perspective.

Scholars from all over the world have considered the shape and space of buildings layout, building orientation, street canyon and many other influencing factors in the wind environment of pedestrian level around the building. A great deal of research has been done, which provides valuable reference for follow-up research. In the initial design stage of Tel Aviv's new business district, Israeli architect Cape Lutois Sac G took sunshine, wind direction, wind speed and other climatic factors into account, and proposed a new design process to reduce the impact of sunshine on building groups, urban roads and business districts [15]. The advantage of the project is that on the one hand, it can provide the business district with a suitable wind environment, on the other hand, it can also meet the residents' requirements in living areas. Tsang et al. used wind tunnel test method to evaluate the wind environment at outdoor pedestrian height of high-rise buildings from three aspects: architectural geometric factors, spacing and podium [16-17]. The research shows that the increase of the height of a single building is conducive to the natural circulation of airflow at pedestrian height, but the increase of width will expand the area of low wind speed zone. When the building width is more than twice the spacing, the increase of building height will affect the natural ventilation and adversely affect the outdoor wind environment. In addition, the podium is unfavorable to the building area which needs natural ventilation. Jonas A et al. analysed the microclimate by studying six different urban topologies, with only the building heights of the individual buildings are changed [18]. The results show that the change of building height will have an obvious impact on the surrounding microclimate, and the temperature change around the building is related to the surrounding air flow and heat diffusion efficiency. T. Stathopoulos indicated that circular and polygon shaped building corner contribute to better wind climate comparing with the square-shaped corner due to reduced downwash [19]. Some other professors concentrated on the wind condition when buildings and the wind direction in different angles, and indicated that the windage resistance of small angles is weak, which will result in higher wind velocity [20-21].

In urban design, different spatial morphology not only affect traffic, but also form different microclimates. Appropriate arrangements of buildings can facilitate comfortable wind environment for pedestrians. M Rohinton Emmanuel focused on climate-sensitive design in tropical areas, and put forward the method of improving urban climate and reducing energy consumption through urban design, and made analysis on how to use architectural layout design to reduce the impact of urban heat island effect, promote the improvement of microclimate around buildings, and make contribution to urban environment, which provided theoretical basis for related research in other different climate regions [22]. Gordon B. Bonan et al. studied the relationship between the density of residential buildings and the wind environment through satellite images on GIS, and concluded that the wind environment in residential areas would be affected by the density of residential buildings and the wind speed in urban areas with high building density would be lower [23-24]. Besides, Kubota et al., Taleghani et al. and Mehdi Shahrestani et al. conducted pedestrian-level wind condition analysis of several typical residential layout modes in Japan, the Netherlands and UK [25-27]. Building arrangements which provided optimal wind environment for each area were proposed in these studies.

With the acceleration of urbanization in China, more and more high-rise buildings are designed for saving construction land. At the same time, urban residents put forward higher requirements for comfortable and safe environment, and the outdoor wind environment in residential areas has gradually attracted the attention of experts. Zhang et al. conducted both CFD simulation and wind tunnel study to explore wind conditions around different building layout, and found that the staggered arrangement facilitate more wind into the site, which can improve natural ventilation in residential area [28]. Some experts in Nanjing and Chongqing pointed out that scattered points layout is helpful for the ventilation due to the less site coverage [29-30]. Shui et al. carried out experiment of the wind condition of 7 residential areas and found that multi-storey residential areas with hybrid-type and the enclosed-type layout are suitable in severe cold regions in China [31]. The published paper containas a vast number of papers on perdestrain level wind environment of residential areas. However, these papers show inconsistent results of different residential layout modes. This is due to these studies were conducted in different thermal zone in China and some of the simulation samples are not combined with the actual situation.

There are three main types of residential area plans in China: determinant layout, enclosing layout and mixed layout. Residential areas generally cover a large area and have a regular layout. According to the planning characteristics of spatial morphology of residential areas in China, the government published some evalution standard and planning restrictions. Design standard for thermal environment of urban residential areas suggests that in I, II, In Ⅲ and Ⅳ building climate zones, residential areas with high building density should be arranged in the upwind direction of the dominant wind direction in winter, in Ⅲ, Ⅳ, Ⅴbuilding climate zones, residential areas with high building density are arranged in the downwind of the dominant wind direction in summer [32]. The assessment standard for green building suggests that in winter, the wind speed and the wind velocity ratio at perdestrain level should lower than 5m/s and 2, and the wind pressure difference between windward side and leeward side of the building is less than 5 Pa, which can reduce the penetration of cold air into the room. In summer, there should be no windless zone in residential quarters, which will affect the heat dissipation of buildings and the dissipation of pollutants. The difference of wind pressure between the inner and outer surfaces of windows should be higher than 0.5 Pa, which will be beneficial to natural ventilation [33]. However, some of the current wind environment research ignored to adhere to the government standard and codes.

In this paper, the layout mode of residential areas which facilitates favorable wind environment in Shenyang is proposed through Computational Fluid Dynamics (CFD) simulation. Firstly, the typical patterns of residential district layout in Shenyang are investigated and summarized, by which the simulation samples are selected. Then, the wind environment of residential district is simulated according to the climatic conditions in Shenyang, and the simulation results are analyzed using Chinese green building evaluation standards. Finally, the architectural layout which is suitable for the climate conditions of Shenyang is put forward. This study will provide more choices for architectural layout in cold regions of China, and will also provide practical suggestions for residential district planning.

Amendment:

• Introduction

In Chinese mega cities, a residential area is one of the most important activity spaces in urban areas. Outdoor ventilation of residential areas is an essential part of urban microclimate studies [1]. At present, the residential areas in many big cities in China are composed of high-rise buildings, which will lead to excessive instantaneous wind speed in some areas. However, High wind speed at pedestrian level can lead to uncomfortable or even dangerous conditions [2-6]. Lawson and Penwarden (1975) has reported the death of two old ladies due to an unfortunate fall caused by high wind velocity at the base of a tall building [7]. Therefore, many government agencies are studying new policies to improve the comfort and safety of wind condition around buildings. A moderate wind environment can not only improve human comfort, but also facilitate the diffusion process of pollutants , contribute to energy conservation and decrease urban heat island [2, 8-14]. Many urban planners have made it is necessary to discuss the pedestrian level wind condition for large urban communities at initial design stage [15-17]. Therefore, it is quite important to evaluate the wind comfort at pedestrian level and obtain an acceptable wind environment from urban planning development perspective.

Shenyang locates in the northeast of China, where the winter is long and severe cold. And it is described as severe cold region in the Code for thermal design of civil building GB 50176-2016 [18]. In winter, strong wind contributes to the the degree of discomfort, espically in severe cold areas. Therefore, it is essential to obtain an adorable wind environment in severe cold regions from the human confort perspective. Liu et al. investigated the prediction model of pedestrian-level wind chill temperature of Chinese high-rise residential areas, and proposed the pedestrain level thermal sensation evaluation of six major cities in Chinese severe cold regions [19]. Jin et al. studied the influence factors of thermal comfort of pedestrain street in severe cold regions of China and suggested that the optimization in winter focuses on blocking the wind [20]. Yang et al. took 31 cities in China as examples to investigate the relationship between urban ventilation and the energy demand from a thermal environment perspective and indicated that good ventilation could reduce the energy demand in the summer and increases the energy demand in the winter [21]. These studies mainly focused on the contribution of urban ventilation on the thermal environment and considered that it is important to control the pedestrain level wind environment of residential areas in severe cold regions in China.

There are three main types of residential plans in China: determinant layout, enclosing layout and mixed layout. Residential areas generally cover a large area and have a regular layout. Shui conducted questionnaire survey of human wind comfort in 7 typical residential areas and suggested that the enclosing layout and the mixed layout are suitable for the multi-storey residential areas in severe cold regions [22]. Although several studies about wind conditions at pedestrain level in cold regions of China have been explored in prior work, the most studies focused on some certain residential areas, the classification of residential areas need to be more comprehensive. It takes time to simulate the wind environment of each residential area in the early stage of design. one good solution is to simplify the current residential layouts into several typical ones for wind environment assessment, which is convenient for architects to choose a suitable layout for in-depth design.

Considering the current trend that more and more high-rise residential areas are built in Shenyang, 12 typical layouts of newly-built high-rise buildings are summarised in this study and the wind environment of each layout is assessed. In this paper, the layout mode of residential areas which facilitates favorable wind environment in Shenyang is proposed through Computational Fluid Dynamics (CFD) simulation. Firstly, the typical patterns of residential district layout in Shenyang are investigated and summarized, by which the simulation samples are selected. Then, the wind environment of residential district is simulated according to the climatic conditions in Shenyang, and the simulation results are analyzed using Chinese green building evaluation standards. Finally, the architectural layout which is suitable for the climate conditions of Shenyang is put forward. This study will provide more choices for architectural layouts in cold regions of China, and will also provide practical suggestions for urban residential planning.

②Literature Review

2.1 Effect of architectural geometric factors

Scholars from all over the world have considered the shape and space of buildings layouts, building orientation, street canyon and many other influencing factors in the wind environment of pedestrian level around the building. A great deal of research have been done, which provides valuable reference for follow-up research. In the initial design stage of Tel Aviv's new business district, Israeli architect Cape Lutois Sac G took sunshine, wind direction, wind speed and other climatic factors into account, and proposed a new design process to reduce the impact of sunshine on building groups, urban roads and business districts [23]. This project can provide the business district with a suitable wind environment, and can also meet the residents' requirements in living areas. Jonas A et al. analysed the microclimate by studying six different urban topologies, with only the building heights of the individual buildings are changed [24]. The results show that the change of building height will have an obvious impact on the surrounding microclimate, and the temperature change around the building is related to the surrounding air flow and heat diffusion efficiency. T. Stathopoulos indicated that circular and polygon shaped building corner contribute to better wind climate comparing with the square-shaped corner due to reduced downwash [25]. Some other professors concentrated on the wind condition when buildings and the wind direction in different angles, and indicated that the windage resistance of small angles is weak, which will result in higher wind velocity [26-27].

2.2 Effect of architectural spatial morphology

In urban design, different spatial morphology not only affect traffic, but also form different microclimates. Appropriate arrangements of buildings can facilitate comfortable wind environment for pedestrians. M Rohinton Emmanuel focused on climate-sensitive design in tropical areas, and put forward the method of improving urban climate and reducing energy consumption through urban design, and made analysis on how to use architectural layout design to reduce the impact of urban heat island effect, promote the improvement of microclimate around buildings, and make contribution to urban environment, which provided theoretical basis for related research in other different climate regions [28]. Gordon B. Bonan et al. studied the relationship between the density of residential buildings and the wind environment through satellite images on GIS, and concluded that the wind environment in residential areas would be affected by the density of residential buildings and the wind speed in urban areas with high building density would be lower [29-30]. Besides, Kubota et al., Taleghani et al. and Mehdi Shahrestani et al. conducted pedestrian-level wind condition analysis of several typical residential layout modes in Japan, the Netherlands and UK [31-33]. Building arrangements which provided optimal wind environment for each area were proposed in these studies.

2.3 Wind environment studies in China

With the acceleration of urbanization in China, more and more high-rise buildings are designed for saving construction land. At the same time, urban residents put forward higher requirements for comfortable and safe environment, and the outdoor wind environment in residential areas has gradually attracted the attention of experts. Zhang et al. conducted both CFD simulation and wind tunnel study to explore wind conditions around different building layout, and found that the staggered arrangement facilitate more wind into the site, which can improve natural ventilation in residential areas [34]. Some experts in Nanjing and Chongqing pointed out that scattered points layout is helpful for the ventilation due to the less site coverage [35-36]. Shui et al. carried out experiment of the wind condition of 7 residential areas and found that multi-storey residential areas with hybrid-type and the enclosed-type layout are suitable in severe cold regions in China [22]. The published paper containas a vast number of papers on perdestrain level wind environment of residential areas. However, more studies were conducted in southern China.

2.4 Codes and standards in China

According to the planning characteristics of spatial morphology of residential areas in China, the government published some evalution standard and planning restrictions. Design standard for thermal environment of urban residential areas suggests that in I, II, In Ⅲ and Ⅳ building climate zones, residential areas with high building density should be arranged in the upwind direction of the dominant wind direction in winter, in Ⅲ, Ⅳ, Ⅴbuilding climate zones, residential areas with high building density are arranged in the downwind of the dominant wind direction in summer [37]. The assessment standard for green building suggests that in winter, the wind speed and the wind velocity ratio at perdestrain level should lower than 5m/s and 2, and the wind pressure difference between windward side and leeward side of the building is less than 5 Pa, which can reduce the penetration of cold air into the room. In summer, there should be no windless zone in residential quarters, which will affect the heat dissipation of buildings and the dissipation of pollutants. The difference of wind pressure between the inner and outer surfaces of windows should be higher than 0.5 Pa, which will be beneficial to natural ventilation [38].

The shortcomings in previous research on urban wind environments in residential areas can be summarized as follows:

• Due to the restriction of economic factors, more and more high-rise residential areas have been built in China. At present, there is a lack of simulation and comparison of wind environment in different planning modes of high-rise residential areas in severe cold regions in China.
• Some of the current wind environment research are mainly at a macroscopic view and ignored to adhere to the government standard and codes.  

This paper summarizes the high-rise residential quarters in Shenyang more comprehensively and simplifies them into a more intuitive model. Through numerical simulation, residential layouts with favourable pedestrian-level wind conditions were obtained for Shenyang's climate condition. The research results can directly guide architectural design from the perspective of urban wind environment.

Point 5:2.1: perhaps state the temperature differences, if they are that obvious.

Response 5: Thank you very much for referees’ reports. The temperature differences is not that obvious in the study, we will consider this factor in the future research.

Point 6:Fig 1: this almost looks like an old figure taken from a different study, given the low quality. Please cite the source if this is the case; if not, please increase image resolution. Additionally, expand the figure caption: there are two lines in the wind rose, which line represents which season?

Response 6:Thank you very much for referees’ reports. We have changed Figure 1 with a clear picture and added the reference of it in the caption.

 

Original:

 

Figure 1. Wind rose of Shenyang.

Amendment:

 

Figure 1. Wind rose of Shenyang. (Data source: Architectural Design Data Set of China.［M］.Beijing. 2017)

 

Point 7:2.2.: Winter is chosen as the evaluation period, but the introduction focuses on heat stress experienced in summer. Why not evaluate both?

Response 7:Thank you very much for referees’ reports.Shenyang locates in the northeast of China, where the winter is long and severe cold. And it is described as severe cold region in the Code for thermal design of civil building GB 50176-2016 [18]. In winter, strong wind contributes to the the degree of discomfort, espically in severe cold areas. Therefore, it is essential to obtain an adorable wind environment in severe cold regions from the human confort perspective. Liu et al. investigated the prediction model of pedestrian-level wind chill temperature of Chinese high-rise residential areas, and proposed the pedestrain level thermal sensation evaluation of six major cities in Chinese severe cold regions [19]. Jin et al. studied the influence factors of thermal comfort of pedestrain street in severe cold regions of China and suggested that the optimization in winter focuses on blocking the wind [20]. Yang et al. took 31 cities in China as examples to investigate the relationship between urban ventilation and the energy demand from a thermal environment perspective and indicated that good ventilation could reduce the energy demand in the summer and increases the energy demand in the winter [21]. These studies mainly focused on the contribution of urban ventilation on the thermal environment and considered that it is important to control the pedestrain level wind environment of residential areas in severe cold regions in China.

In this study, the winter wind environment of different kinds of residential buildings in Shenyang is simulated and analyzed. However, due to the high requirements for wind protection in winter in northern China, and the outdoor wind environment in summer is not clearly defined in the architectural design requirements, the wind environment of residential buildings has not been explored. We will consider evaluating the summer condition in future research.

Point 8:2.2: too many subheaders, merge some.

Point 9:2.1: perhaps include a schematic overview of the building layouts in the model. Include a reference to the FLUENT model?

Point 10:Table 2: there is no table 1, please re-number. Also, related to the previous point: this table nicely shows the building layouts, but it would be good to see them in the model domain.

Point 11:What is the vertical extent of the model? Is it high enough for correct boundary layer development and vertical downdrafts into street canyons?

Point 12:Figs 2-4: legends are hard to read, increase the sizes of those (and the figures themselves, it’s hard to see the vectors).

Response 8-12 :Thank you very much for referees’ reports. Point 8-12 are in the Materials and Method section. According to the review questions, we modified this section carefully.

Original:

2. Materials and Methods

2.1. Study Area

Shenyang is the capital of Liaoning Province, the economic, cultural, transportation, financial and commercial center of Northeast China, and also an important industrial base and historical and cultural city in China. It is located in the south of Northeast China (42°21’N, 123°28’ E), with a continental monsoon climate in North temperate zone, cold in winter and warm in summer. The cold period is long, spring and autumn are short and windy. The temperature difference in four seasons is obvious in Shenyang. The annual mean temperature and humidity is 8.1℃, and 63% respectively. Figure 1 is the wind rose map of Shenyang, from which we can see that he wind direction is relatively stable all year round, and the maximum wind direction is mainly from south in summer and north in winter.

 

Figure 1. Wind rose of Shenyang.

Due to the special climatic conditions, the buildings in Shenyang have the following characteristics: Traditional dwellings are thick and closed, usually the thickness of the external wall is more than 370mm. The courtyard is open, and the buildings only open windows to the courtyard, so as to effectively prevent the invasion of cold wind in winter. At present, The thickness of modern building block wall and insulation is generally 200mm to 300mm, and 50 mm to 80 mm, respectively. The building shape coefficient is relatively small to reduce the heat dissipation area, and the winter heat preservation requirements are mainly considered in the building design process.

2.2. Methods

In this paper, CFD fluent software is used to simulate the building wind environment formed by different architectural layout, which include slab buildings arrangement, point buildings arrangement and slab-point combination buildings arrangement. By analyzing and comparing the wind velocity ratio, wind velocity vector map and wind pressure at pedestrian height, the relationship between the wind environment and the plane layout can be obtained. In addition, the wind pressure diagram is used to analyze the heat preservation of building envelope, which provides reference and evaluation basis for the planning and layout of residential areas in Shenyang. Combining with the actual situation in Shenyang, this study takes winter as the main evaluation season. According to the Architectural Design Data Set of China, the dominant wind direction in winter is north , and the average wind velocity is 3.0m/s.

2.2.1. Selection of calculation model

In order to prevent the treatment of each outflow boundary condition from affecting the actual flow field distribution around the building, and at the same time ensure that the inflow surface is not affected by the building, so that the influence of the building on the flow around in this area is completely eliminated at the boundary, and finally ensure that the inflow and outflow control bodies realize mass conservation, a larger simulation space should be adopted in the calculation domain. In this way, the two-dimensional flow field is selected for simulation, and the buildings are placed in the range of X×Y =360×500(m) according to the size selection method of calculation domain.

2.2.2. Model selection and grid division

The outdoor airflow at the bottom of the atmosphere is generally in the range of low-speed flow, and the air can be assumed as Boussinesq, which is a viscous and incompressible fluid. The standard κ -ε model is selected to simulate the wind environment of buildings. GAMBIT pre-processing software of FLUENT is used for grid division. Line grids and area grids are divided for buildings and peripheral large-scale computational domains, dense grids are arranged near solid areas, and sparse grids are adopted in areas far away from the model, and all grids are triangles.

2.2.3. Reference pressure position setting

A reference pressure position should be set due to incompressible flow. Regardless of the gravity influence, operating pressure is set to the standard atmospheric pressure of 101325Pa.

2.2.4. Selection of boundary conditions

Velocity inlet is selected as the entrance boundary condition, and the velocity value is 3m/s, which is the dominant wind velocity in winter. Outlet boundary condition is selected as outflow, which is suitable for the case where the pressure or velocity on the outlet boundary is unknown.

According to the actual typical buildings layout condition in Shrenyang, slab buildings and point buildings are selected as simulation samples. The two kinds of buildingsare simplified into regular quadrangles before simulation, and the sizes of point buildings and slab buildings are respectively 20m×20m×60m (length×width×height) and 45m×15m×60m. The specific arrangement is shown in Table 1.

Table 2. The building arrangements for simulation

2.2.5. Evaluation standard of wind velocity ratio

In practical application, wind velocity ratio (wind speed amplification) is used as comfort parameter to discuss the comfort of wind environment around buildings. Wind velocity ratio reflects the degree of wind velocity change caused by the existence of buildings. Wind velocity ratio Ri is defined as:

Ri=Vi／Vo

Where Ri is the ratio of wind velocity at the position of i point (dimensionless), Vi is Average wind velocity at pedestrian height at point i in the flow field, Vo is average wind velocity of undisturbed incoming flow at pedestrian height, generally the initial wind velocity.

Wind velocity ratio evaluation is a common evaluation standard of wind comfort. This study will use this index to discuss the outdoor wind environment comfort of Shenyang residential area under different arrangement forms.

 

Amendment:

3. Materials and Methods

3.1. Study Area

Shenyang is the capital of Liaoning Province, the economic, cultural, transportation, financial and commercial center of Northeast China, and also an important industrial base and historical and cultural city in China. It is located in the south of Northeast China (42°21’N, 123°28’ E), with a continental monsoon climate in North temperate zone, cold in winter and warm in summer. The cold period is long, spring and autumn are short and windy. The temperature difference in four seasons is obvious in Shenyang. The annual mean temperature and humidity is 8.1℃, and 63% respectively. Figure 1 is the wind rose map of Shenyang, from which we can see that the wind direction is relatively stable all year round, and the maximum wind direction is mainly from south in summer and north in winter.

Due to the special climatic conditions, the buildings in Shenyang have the following characteristics: Traditional dwellings are thick and closed, usually the thickness of the external wall is more than 370mm. The courtyard is open, and the buildings only open windows to the courtyard, so as to effectively prevent the invasion of cold wind in winter. At present, The thickness of modern building block wall and insulation is generally 200mm to 300mm, and 50 mm to 80 mm, respectively. The building shape coefficient is relatively small to reduce the heat dissipation area, and the winter heat preservation requirements are mainly considered in the building design process.

Figure 1. Wind rose of Shenyang.(Data source: Architectural Design Data Set of China.［M］.Beijing. 2017)

 

3.2. Methods

In this paper, CFD fluent software [44] is used to simulate the building wind environment formed by different architectural layouts. Through the investigation of more than 50 residential areas in Shenyang, it is found that the newly-built residential areas in Shenyang are mainly composed of slab buildings , point buildings amd slab-point combination buildings (Figure 2). 

 

Figure 2: Some high rise residential areas in Shenyang (Data source: Drawn by author)

 

Slab buildings and point buildings are two common forms of high-rise buildings in Shenyang. It can be seen from the Figure 3 that the slab building is that the length of the building is far greater than the width and looks like a piece of slab in general plan, while the point building is that the length and width of the building are similar in size and it looks like a square point in general plan. By analyzing and comparing the wind velocity ratio, wind velocity vector map and wind pressure at pedestrian height, the relationship between the wind environment and the plane layouts can be obtained. In addition, the wind pressure diagram is used to analyze the heat preservation of building envelope, which provides reference and evaluation basis for the planning and layout of residential areas in Shenyang.

 Figure 3: Slab buildings and Point buildings (Data source: Drawn by author)

Nowdays, the construction departments of Shenyang encourage the construction of high-rise buildings in the city center for saving construction land. However, More and more high-rise buildings may cause complex wind environment, and in winter when the temperature is low, the high wind speed in the residential areas may cause discomfort to pedestrians. In consideration of this situation in Shenyang, this study takes winter as the main evaluation season. According to the Architectural Design Data Set of China [39], the dominant wind direction in winter is north , and the average wind velocity is 3.0m/s.

3.2.1. Computational domain and grids

The size of calculation area will directly affect the accuracy of simulation. If the calculation area is small, the flow field will be distorted. A large calculation area will result in many grids and increase the calculation amount and cost. According to relevant experience at home and abroad, the simulation area is set at 360m×500m, and the calculation height is 5 times of the building height [22, 40-41].  The outdoor airflow at the bottom of the atmosphere is generally in the range of low-speed flow, and the air can be assumed as Boussinesq, which is a viscous and incompressible fluid. Generally, CFD software is equipped with various turbulence models, and k-ε model is the most widely used one for engineering applications. It has low calculation cost, small fluctuation and high precision in numerical calculation [42]. DB11 /938-2012 Standard for Green Building Design (Beijing) suggests that the standard k-ε model can be used when the calculation accuracy is not high and only the flow field at a height of 1. 5 m is concerned [43]. Therefore, the standard k-ε model is selected in this study to simulate the wind environment of buildings. GAMBIT pre-processing software [44] of FLUENT is used for grid division. Line grids and area grids are divided for buildings and peripheral large-scale computational domains, dense grids are arranged near solid areas, and sparse grids are adopted in areas far away from the model, and all grids are triangles. A reference pressure position should be set due to incompressible flow. Regardless of the gravity influence, operating pressure is set to the standard atmospheric pressure of 101325Pa.

3.2.2. Building arrangements for simulation

According to the typical buildings layouts condition in Shenyang, this study summerisd 12 kinds of layouts for numerial simulation . The two kinds of buildings are simplified into regular quadrangles before simulation, and the sizes of point buildings and slab buildings are respectively 20m×20m×60m (length×width×height) and 45m×15m×60m. The specific arrangement is shown in Table 1.

Table 1. The building arrangements for simulation

3.2.3. Evaluation standard of wind velocity ratio

In practical application, wind velocity ratio (wind speed amplification) is used as comfort parameter to discuss the comfort of wind environment around buildings [38]. Wind velocity ratio reflects the degree of wind velocity change caused by the existence of buildings. Wind velocity ratio Ri is defined as:

Ri=Vi／Vo

Where Ri is the ratio of wind velocity at the position of i point (dimensionless), Vi is Average wind velocity at pedestrian height at point i in the flow field, Vo is average wind velocity of undisturbed incoming flow at pedestrian height, generally the initial wind velocity.

Wind velocity ratio evaluation is a common evaluation standard of wind comfort. This study will use this index to discuss the outdoor wind environment comfort of Shenyang residential area under different arrangement forms.

 

Point 13:Results: interesting to see the effect of these configurations side by side and how they impact the wind field. However, in a real city there is also a strong vertical component of the wind, especially when it hits a frontal surface and needs to go around it. This isn’t researched at all, even though it seems the most obvious one to me. While I can understand the limits of what can be put in a single paper, this at least bears some thorough discussion: why have you chosen to omit this part of the wind field?

Response 13:Thank you very much for referees’ reports.The main purpose of this paper is to simulate the wind environment around the buildings, and select the layouts  with better wind environment in winter, so as to reduce the discomfort caused by wind speed. We will consider the vertical component of the wind in future research.

Point 14:4.2: what are “landscape sketches” and how will they help against wind nuisance? Have you tested any of these suggested implementations in the model?

Response 14: Thank you very much for referees’ reports. I seriously pondered the expression of this word in the article and found that there were indeed questions raised by the reviewer.We modified this word with “landscape design”. The landscape design in the central area could reduce the adverse effects brought by channel wind. This paper focus on the wind environment of different architecture layouts. We will test the wind environment of residential areas with different landscape design in future work.

Author Response File: Author Response.pdf

Reviewer 4 Report

1. Abstract: it is good.
2. Background:
   • The background is too long due to the literature review contents and lacks concise. Thus, it is so boring to read. It is better to separate into 2 sections: introduction and literate review. Moreover, there is a need to divide the literature review section into subsections regarding research topic, numerical simulation, etc.
   • Please explain why authors apply numerical simulation for this topic, as well as emphasize the importance to research the wind environment assessment of Shenyang's residential area.
   • Please state research questions.
3. Materials and Methods
   • In table 2, the building arrangements are in Shenyang or proposed by authors for simulation? Please explain in manuscript.
4. Conclusion: Conclusion needs to be improved by providing key recommendations for future work.
5. References: some references are too old. Please replace the new ones.
6. There is some typing mistakes (e.g. Shrenyang, space between words, etc.). Please check carefully.

Author Response

Point 1: Abstract: it is good.

Point 2: Background: The background is too long due to the literature review contents and lacks concise. Thus, it is so boring to read. It is better to separate into 2 sections: introduction and literate review. Moreover, there is a need to divide the literature review section into subsections regarding research topic, numerical simulation, etc.

Please explain why authors apply numerical simulation for this topic, as well as emphasize the importance to research the wind environment assessment of Shenyang's residential area. Please state research questions.

Response 1: Thank you very much for referees’ reports. I seriously pondered the issue of the Introduction section, and felt that there was a problem with the previous writing method. Therefore, the full text was carefully modified. The revision consists of two parts, which are the Introduction (marked as①) and Literature review (marked as②). 

After summarizing the previous research on urban wind environments in residential areas, we find that due to the restriction of economic factors, more and more high-rise residential areas have been built in China. At present, there is a lack of simulation and comparison of wind environment in different planning modes of high-rise residential areas in severe cold regions in China. Besides, some of the current wind environment research are mainly at macroscopic view and ignored to adhere to the government standard and codes. This study can provide guidance for the plan of residential areas in Shenyang by simulating different kinds of architecture layouts. That is why the study of wind environment of residential areas in Shenyang should be done. The research questions are stated in Literature review section.

 

Original: In Chinese mega cities, residential areas are one of the most important activity spaces in urban areas. Outdoor ventilation of residential area is an essential part of urban microclimate studies [1]. At present, the residential areas in many big cities in China are composed of high-rise buildings, which will lead to excessive instantaneous wind speed in some areas. However, High wind speed at pedestrian level can lead to uncomfortable or even dangerous conditions [2-6]. Lawson and Penwarden (1975) has reported the death of two old ladies due to an unfortunate fall caused by high wind velocity at the base of a tall building [7]. Therefore, many government agencies are studying new policies to improve the comfort and safety of wind condition around buildings. A moderate wind environment can not only improve human comfort, but also facilitate the diffusion process of pollutants , contribute to energy conservation and decrease urban heat island [2, 8-11]. Many urban planners have made it is necessary to discuss the pedestrian level wind condition for large urban communities at initial design stage [12-14]. Therefore, it is quite important to evaluate the wind comfort at pedestrian level and obtain an acceptable wind environment from urban planning development perspective.

Scholars from all over the world have considered the shape and space of buildings layout, building orientation, street canyon and many other influencing factors in the wind environment of pedestrian level around the building. A great deal of research has been done, which provides valuable reference for follow-up research. In the initial design stage of Tel Aviv's new business district, Israeli architect Cape Lutois Sac G took sunshine, wind direction, wind speed and other climatic factors into account, and proposed a new design process to reduce the impact of sunshine on building groups, urban roads and business districts [15]. The advantage of the project is that on the one hand, it can provide the business district with a suitable wind environment, on the other hand, it can also meet the residents' requirements in living areas. Tsang et al. used wind tunnel test method to evaluate the wind environment at outdoor pedestrian height of high-rise buildings from three aspects: architectural geometric factors, spacing and podium [16-17]. The research shows that the increase of the height of a single building is conducive to the natural circulation of airflow at pedestrian height, but the increase of width will expand the area of low wind speed zone. When the building width is more than twice the spacing, the increase of building height will affect the natural ventilation and adversely affect the outdoor wind environment. In addition, the podium is unfavorable to the building area which needs natural ventilation. Jonas A et al. analysed the microclimate by studying six different urban topologies, with only the building heights of the individual buildings are changed [18]. The results show that the change of building height will have an obvious impact on the surrounding microclimate, and the temperature change around the building is related to the surrounding air flow and heat diffusion efficiency. T. Stathopoulos indicated that circular and polygon shaped building corner contribute to better wind climate comparing with the square-shaped corner due to reduced downwash [19]. Some other professors concentrated on the wind condition when buildings and the wind direction in different angles, and indicated that the windage resistance of small angles is weak, which will result in higher wind velocity [20-21].

In urban design, different spatial morphology not only affect traffic, but also form different microclimates. Appropriate arrangements of buildings can facilitate comfortable wind environment for pedestrians. M Rohinton Emmanuel focused on climate-sensitive design in tropical areas, and put forward the method of improving urban climate and reducing energy consumption through urban design, and made analysis on how to use architectural layout design to reduce the impact of urban heat island effect, promote the improvement of microclimate around buildings, and make contribution to urban environment, which provided theoretical basis for related research in other different climate regions [22]. Gordon B. Bonan et al. studied the relationship between the density of residential buildings and the wind environment through satellite images on GIS, and concluded that the wind environment in residential areas would be affected by the density of residential buildings and the wind speed in urban areas with high building density would be lower [23-24]. Besides, Kubota et al., Taleghani et al. and Mehdi Shahrestani et al. conducted pedestrian-level wind condition analysis of several typical residential layout modes in Japan, the Netherlands and UK [25-27]. Building arrangements which provided optimal wind environment for each area were proposed in these studies.

With the acceleration of urbanization in China, more and more high-rise buildings are designed for saving construction land. At the same time, urban residents put forward higher requirements for comfortable and safe environment, and the outdoor wind environment in residential areas has gradually attracted the attention of experts. Zhang et al. conducted both CFD simulation and wind tunnel study to explore wind conditions around different building layout, and found that the staggered arrangement facilitate more wind into the site, which can improve natural ventilation in residential area [28]. Some experts in Nanjing and Chongqing pointed out that scattered points layout is helpful for the ventilation due to the less site coverage [29-30]. Shui et al. carried out experiment of the wind condition of 7 residential areas and found that multi-storey residential areas with hybrid-type and the enclosed-type layout are suitable in severe cold regions in China [31]. The published paper containas a vast number of papers on perdestrain level wind environment of residential areas. However, these papers show inconsistent results of different residential layout modes. This is due to these studies were conducted in different thermal zone in China and some of the simulation samples are not combined with the actual situation.

There are three main types of residential area plans in China: determinant layout, enclosing layout and mixed layout. Residential areas generally cover a large area and have a regular layout. According to the planning characteristics of spatial morphology of residential areas in China, the government published some evalution standard and planning restrictions. Design standard for thermal environment of urban residential areas suggests that in I, II, In Ⅲ and Ⅳ building climate zones, residential areas with high building density should be arranged in the upwind direction of the dominant wind direction in winter, in Ⅲ, Ⅳ, Ⅴbuilding climate zones, residential areas with high building density are arranged in the downwind of the dominant wind direction in summer [32]. The assessment standard for green building suggests that in winter, the wind speed and the wind velocity ratio at perdestrain level should lower than 5m/s and 2, and the wind pressure difference between windward side and leeward side of the building is less than 5 Pa, which can reduce the penetration of cold air into the room. In summer, there should be no windless zone in residential quarters, which will affect the heat dissipation of buildings and the dissipation of pollutants. The difference of wind pressure between the inner and outer surfaces of windows should be higher than 0.5 Pa, which will be beneficial to natural ventilation [33]. However, some of the current wind environment research ignored to adhere to the government standard and codes.

In this paper, the layout mode of residential areas which facilitates favorable wind environment in Shenyang is proposed through Computational Fluid Dynamics (CFD) simulation. Firstly, the typical patterns of residential district layout in Shenyang are investigated and summarized, by which the simulation samples are selected. Then, the wind environment of residential district is simulated according to the climatic conditions in Shenyang, and the simulation results are analyzed using Chinese green building evaluation standards. Finally, the architectural layout which is suitable for the climate conditions of Shenyang is put forward. This study will provide more choices for architectural layout in cold regions of China, and will also provide practical suggestions for residential district planning.

Amendment:

• Introduction

In Chinese mega cities, a residential area is one of the most important activity spaces in urban areas. Outdoor ventilation of residential areas is an essential part of urban microclimate studies [1]. At present, the residential areas in many big cities in China are composed of high-rise buildings, which will lead to excessive instantaneous wind speed in some areas. However, High wind speed at pedestrian level can lead to uncomfortable or even dangerous conditions [2-6]. Lawson and Penwarden (1975) has reported the death of two old ladies due to an unfortunate fall caused by high wind velocity at the base of a tall building [7]. Therefore, many government agencies are studying new policies to improve the comfort and safety of wind condition around buildings. A moderate wind environment can not only improve human comfort, but also facilitate the diffusion process of pollutants , contribute to energy conservation and decrease urban heat island [2, 8-14]. Many urban planners have made it is necessary to discuss the pedestrian level wind condition for large urban communities at initial design stage [15-17]. Therefore, it is quite important to evaluate the wind comfort at pedestrian level and obtain an acceptable wind environment from urban planning development perspective.

Shenyang locates in the northeast of China, where the winter is long and severe cold. And it is described as severe cold region in the Code for thermal design of civil building GB 50176-2016 [18]. In winter, strong wind contributes to the the degree of discomfort, espically in severe cold areas. Therefore, it is essential to obtain an adorable wind environment in severe cold regions from the human confort perspective. Liu et al. investigated the prediction model of pedestrian-level wind chill temperature of Chinese high-rise residential areas, and proposed the pedestrain level thermal sensation evaluation of six major cities in Chinese severe cold regions [19]. Jin et al. studied the influence factors of thermal comfort of pedestrain street in severe cold regions of China and suggested that the optimization in winter focuses on blocking the wind [20]. Yang et al. took 31 cities in China as examples to investigate the relationship between urban ventilation and the energy demand from a thermal environment perspective and indicated that good ventilation could reduce the energy demand in the summer and increases the energy demand in the winter [21]. These studies mainly focused on the contribution of urban ventilation on the thermal environment and considered that it is important to control the pedestrain level wind environment of residential areas in severe cold regions in China.

There are three main types of residential plans in China: determinant layout, enclosing layout and mixed layout. Residential areas generally cover a large area and have a regular layout. Shui conducted questionnaire survey of human wind comfort in 7 typical residential areas and suggested that the enclosing layout and the mixed layout are suitable for the multi-storey residential areas in severe cold regions [22]. Although several studies about wind conditions at pedestrain level in cold regions of China have been explored in prior work, the most studies focused on some certain residential areas, the classification of residential areas need to be more comprehensive. It takes time to simulate the wind environment of each residential area in the early stage of design. one good solution is to simplify the current residential layouts into several typical ones for wind environment assessment, which is convenient for architects to choose a suitable layout for in-depth design.

Considering the current trend that more and more high-rise residential areas are built in Shenyang, 12 typical layouts of newly-built high-rise buildings are summarised in this study and the wind environment of each layout is assessed. In this paper, the layout mode of residential areas which facilitates favorable wind environment in Shenyang is proposed through Computational Fluid Dynamics (CFD) simulation. Firstly, the typical patterns of residential district layout in Shenyang are investigated and summarized, by which the simulation samples are selected. Then, the wind environment of residential district is simulated according to the climatic conditions in Shenyang, and the simulation results are analyzed using Chinese green building evaluation standards. Finally, the architectural layout which is suitable for the climate conditions of Shenyang is put forward. This study will provide more choices for architectural layouts in cold regions of China, and will also provide practical suggestions for urban residential planning.

②Literature Review

2.1 Effect of architectural geometric factors

Scholars from all over the world have considered the shape and space of buildings layouts, building orientation, street canyon and many other influencing factors in the wind environment of pedestrian level around the building. A great deal of research have been done, which provides valuable reference for follow-up research. In the initial design stage of Tel Aviv's new business district, Israeli architect Cape Lutois Sac G took sunshine, wind direction, wind speed and other climatic factors into account, and proposed a new design process to reduce the impact of sunshine on building groups, urban roads and business districts [23]. This project can provide the business district with a suitable wind environment, and can also meet the residents' requirements in living areas. Jonas A et al. analysed the microclimate by studying six different urban topologies, with only the building heights of the individual buildings are changed [24]. The results show that the change of building height will have an obvious impact on the surrounding microclimate, and the temperature change around the building is related to the surrounding air flow and heat diffusion efficiency. T. Stathopoulos indicated that circular and polygon shaped building corner contribute to better wind climate comparing with the square-shaped corner due to reduced downwash [25]. Some other professors concentrated on the wind condition when buildings and the wind direction in different angles, and indicated that the windage resistance of small angles is weak, which will result in higher wind velocity [26-27].

2.2 Effect of architectural spatial morphology

In urban design, different spatial morphology not only affect traffic, but also form different microclimates. Appropriate arrangements of buildings can facilitate comfortable wind environment for pedestrians. M Rohinton Emmanuel focused on climate-sensitive design in tropical areas, and put forward the method of improving urban climate and reducing energy consumption through urban design, and made analysis on how to use architectural layout design to reduce the impact of urban heat island effect, promote the improvement of microclimate around buildings, and make contribution to urban environment, which provided theoretical basis for related research in other different climate regions [28]. Gordon B. Bonan et al. studied the relationship between the density of residential buildings and the wind environment through satellite images on GIS, and concluded that the wind environment in residential areas would be affected by the density of residential buildings and the wind speed in urban areas with high building density would be lower [29-30]. Besides, Kubota et al., Taleghani et al. and Mehdi Shahrestani et al. conducted pedestrian-level wind condition analysis of several typical residential layout modes in Japan, the Netherlands and UK [31-33]. Building arrangements which provided optimal wind environment for each area were proposed in these studies.

2.3 Wind environment studies in China

With the acceleration of urbanization in China, more and more high-rise buildings are designed for saving construction land. At the same time, urban residents put forward higher requirements for comfortable and safe environment, and the outdoor wind environment in residential areas has gradually attracted the attention of experts. Zhang et al. conducted both CFD simulation and wind tunnel study to explore wind conditions around different building layout, and found that the staggered arrangement facilitate more wind into the site, which can improve natural ventilation in residential areas [34]. Some experts in Nanjing and Chongqing pointed out that scattered points layout is helpful for the ventilation due to the less site coverage [35-36]. Shui et al. carried out experiment of the wind condition of 7 residential areas and found that multi-storey residential areas with hybrid-type and the enclosed-type layout are suitable in severe cold regions in China [22]. The published paper containas a vast number of papers on perdestrain level wind environment of residential areas. However, more studies were conducted in southern China.

2.4 Codes and standards in China

According to the planning characteristics of spatial morphology of residential areas in China, the government published some evalution standard and planning restrictions. Design standard for thermal environment of urban residential areas suggests that in I, II, In Ⅲ and Ⅳ building climate zones, residential areas with high building density should be arranged in the upwind direction of the dominant wind direction in winter, in Ⅲ, Ⅳ, Ⅴbuilding climate zones, residential areas with high building density are arranged in the downwind of the dominant wind direction in summer [37]. The assessment standard for green building suggests that in winter, the wind speed and the wind velocity ratio at perdestrain level should lower than 5m/s and 2, and the wind pressure difference between windward side and leeward side of the building is less than 5 Pa, which can reduce the penetration of cold air into the room. In summer, there should be no windless zone in residential quarters, which will affect the heat dissipation of buildings and the dissipation of pollutants. The difference of wind pressure between the inner and outer surfaces of windows should be higher than 0.5 Pa, which will be beneficial to natural ventilation [38].

The shortcomings in previous research on urban wind environments in residential areas can be summarized as follows:

• Due to the restriction of economic factors, more and more high-rise residential areas have been built in China. At present, there is a lack of simulation and comparison of wind environment in different planning modes of high-rise residential areas in severe cold regions in China.
• Some of the current wind environment research are mainly at a macroscopic view and ignored to adhere to the government standard and codes.  

This paper summarizes the high-rise residential quarters in Shenyang more comprehensively and simplifies them into a more intuitive model. Through numerical simulation, residential layouts with favourable pedestrian-level wind conditions were obtained for Shenyang's climate condition. The research results can directly guide architectural design from the perspective of urban wind environment.

 

 

Point 3: Materials and Methods

In table 2, the building arrangements are in Shenyang or proposed by authors for simulation? Please explain in manuscript.

Response 2: Thank you very much for referees’ reports. We propose 12 typical combination forms from the investigation of more than 50 residential areas and put forward the wind environment accessment of them.

Amendment:

3.2. Methods

In this paper, CFD fluent software [44] is used to simulate the building wind environment formed by different architectural layouts. Through the investigation of more than 50 residential areas in Shenyang, it is found that the newly-built residential areas in Shenyang are mainly composed of slab buildings , point buildings amd slab-point combination buildings (Figure 2). 

 

 

 

 

 

 

Figure 2: Some high rise residential areas in Shenyang (Data source: Drawn by author)

 

Slab buildings and point buildings are two common forms of high-rise buildings in Shenyang. It can be seen from the Figure 3 that the slab building is that the length of the building is far greater than the width and looks like a piece of slab in general plan, while the point building is that the length and width of the building are similar in size and it looks like a square point in general plan. By analyzing and comparing the wind velocity ratio, wind velocity vector map and wind pressure at pedestrian height, the relationship between the wind environment and the plane layouts can be obtained. In addition, the wind pressure diagram is used to analyze the heat preservation of building envelope, which provides reference and evaluation basis for the planning and layout of residential areas in Shenyang.

 Figure 3: Slab buildings and Point buildings (Data source: Drawn by author)

Nowdays, the construction departments of Shenyang encourage the construction of high-rise buildings in the city center for saving construction land. However, More and more high-rise buildings may cause complex wind environment, and in winter when the temperature is low, the high wind speed in the residential areas may cause discomfort to pedestrians. In consideration of this situation in Shenyang, this study takes winter as the main evaluation season. According to the Architectural Design Data Set of China [39], the dominant wind direction in winter is north , and the average wind velocity is 3.0m/s.

3.2.1. Computational domain and grids

The size of calculation area will directly affect the accuracy of simulation. If the calculation area is small, the flow field will be distorted. A large calculation area will result in many grids and increase the calculation amount and cost. According to relevant experience at home and abroad, the simulation area is set at 360m×500m, and the calculation height is 5 times of the building height [22, 40-41].  The outdoor airflow at the bottom of the atmosphere is generally in the range of low-speed flow, and the air can be assumed as Boussinesq, which is a viscous and incompressible fluid. Generally, CFD software is equipped with various turbulence models, and k-ε model is the most widely used one for engineering applications. It has low calculation cost, small fluctuation and high precision in numerical calculation [42]. DB11 /938-2012 Standard for Green Building Design (Beijing) suggests that the standard k-ε model can be used when the calculation accuracy is not high and only the flow field at a height of 1. 5 m is concerned [43]. Therefore, the standard k-ε model is selected in this study to simulate the wind environment of buildings. GAMBIT pre-processing software [44] of FLUENT is used for grid division. Line grids and area grids are divided for buildings and peripheral large-scale computational domains, dense grids are arranged near solid areas, and sparse grids are adopted in areas far away from the model, and all grids are triangles. A reference pressure position should be set due to incompressible flow. Regardless of the gravity influence, operating pressure is set to the standard atmospheric pressure of 101325Pa.

3.2.2. Building arrangements for simulation

According to the typical buildings layouts condition in Shenyang, this study summerisd 12 kinds of layouts for numerial simulation. The two kinds of buildings are simplified into regular quadrangles before simulation, and the sizes of point buildings and slab buildings are respectively 20m×20m×60m (length×width×height) and 45m×15m×60m. The specific arrangement is shown in Table 1.

Table 1. The building arrangements for simulation

3.2.3. Evaluation standard of wind velocity ratio

 

Point 4:Conclusion: Conclusion needs to be improved by providing key recommendations for future work.

Response 4: Thank you very much for referees’ reports. This study investigated the wind environment of resifential areas of different architecture arrangement based on CFD fluent software. Under the combination of different buildings, the wind environment in the site is quite different. This study recommended three kinds of arrangement and combination forms suitable for residential buildings in Shenyang area, all of which can ensure a favorable wind environment in the case of strong cold wind in winter. However, due to the high requirements for wind protection in winter in northern China, and the outdoor wind environment in summer is not clearly defined in the architectural design requirements, the wind environment of residential buildings has not been explored. Besides, This study focus on the wind velocity conditions at pedestrain level was limited to buildings with fixed and identical dimensions, further research is needed to expand the validity of the present study.

Point 5:References: some references are too old. Please replace the new ones.

Response 4: Thank you very much for referees’ reports. We have replaced some new references in this manuscript.

Original:

References

1. Ma T , Chen T. Classification and pedestrian-level wind environment assessment among Tianjin's residential area based on numerical simulation - ScienceDirect[J]. Urban Climate, 34.
2. Moonen P, Defraeye T,Dorer V, et al. Urban Physics: Effect of the micro-climate on comfort, health and energy demand[J]. Frontiers of Architectural Research, 2012, 1(003):197-228.
3. Niu J, Liu J, Lee T C, et al. A new method to assess spatial variations of outdoor thermal comfort: Onsite monitoring results and implications for precinct planning[J]. Building & Environment, 2015, 91:263-270.
4. Stathopoulos Pedestrian level winds and outdoor human comfort[J]. Journal of Wind Engineering & Industrial Aerodynamics, 2006, 94(11):769-780.
5. BBlocken, TStathopoulos, Beeck J. Pedestrian-level wind conditions around buildings:Review of wind-tunnel and CFD techniques and their accuracy for wind comfort assessment[J]. Building Energy Efficiency, 2016.
6. Iqbal Q, Chan A L S. Pedestrian level wind environment assessment around group of high-rise cross-shaped buildings: Effect of building shape, separation and orientation[J]. Building & Environment, 2016, 101(may):45-63.
7. Lawson T V, Penwar De N A D. The effects of wind on people in the vicinity of buildings. 1975.
8. Ai Z T, Mak C M. CFD simulation of flow in a long street canyon under a perpendicular wind direction: Evaluation of three computational settings[J]. Building and Environment, 2017, 114:293-306.
9. Wu Y, Niu J. Numerical study of inter-building dispersion in residential environments: Prediction methods evaluation and infectious risk assessment[J]. Building & Environment, 2017, 115:199-214.
10. Yang X, Zhao L, Bruse M, et al. APPLICATION OF URBAN MICROCLIMATE SIMULATION DATA IN ASSESSING BUILDING ENERGY CONSUMPTION[J]. Acta Energiae Solaris Sinica, 2015, 36(6):1344-1351.
11. Hong B, Lin B, Lin J. Quantification of residential design parameters' effects on the outdoor wind environment using orthogonal experimental design (OED) and numerical simulation[J]. Procedia Engineering, 2017, 205:137-144.
12. Zhang X, Tse K T, Weerasuriya A U, et al. Evaluation of pedestrian wind comfort near 'lift-up' buildings with different aspect ratios and central core modifications[J]. Building & Environment, 2017, 124:245-257.
13. Wu H, Kriksic F. Designing for pedestrian comfort in response to local climate[J]. Journal of Wind Engineering and Industrial Aerodynamics, 2012, s 104–106(3):397-407.
14. An K, Fung J, Yim S. Sensitivity of inflow boundary conditions on downstream wind and turbulence profiles through building obstacles using a CFD approach[J]. Journal of Wind Engineering & Industrial Aerodynamics, 2013, 115(4):137-149.
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16. A C W T, B K C S K A, A P A H. Wind tunnel study of pedestrian level wind environment around tall buildings: Effects of building dimensions, separation and podium[J]. Building and Environment, 2012, 49(3):167-181.
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19. Stathopoulos T. Wind environmental conditions around tall buildings with chamfered corners[J]. Journal of Wind Engineering & Industrial Aerodynamics, 1985, 21(1):71-87.
20. Ng E, Chao Y, Liang C, et al. Improving the wind environment in high-density cities by understanding urban morphology and surface roughness: A study in Hong Kong[J]. Landscape & Urban Planning, 2011, 101(1):59-74.
21. Bo H, Lin B. Numerical studies of the outdoor wind environment and thermal comfort at pedestrian level in housing blocks with different building layout patterns and trees arrangement[J]. Renewable Energy, 2015, 73(jan.):18-27.
22. Emmanuel, Rohinton M . An Urban Approach To Climate Sensitive Design[M]. 2005.
23. Bonan G B. The microclimates of a suburban Colorado (USA) landscape and implications for planning and design[J]. Landscape and Urban Planning, 2000.
24. Kantzioura A, Kosmopoulos P, Zoras S . Urban surface temperature and microclimate measurements in Thessaloniki[J]. Energy and Buildings, 2012, 44(Jan.):63-72.
25. Kubota T, Miura M, Tominaga Y, et al. Wind tunnel tests on the relationship between building density and pedestrian-level wind velocity: Development of guidelines for realizing acceptable wind environment in residential neighborhoods[J]. Building & Environment, 2008, 43(10):1699-1708.
26. Taleghani M, Kleerekoper L, Tenpierik M, et al. Outdoor thermal comfort within five different urban forms in the Netherlands[J]. Building & Environment, 2015, 83(jan.):65-78.
27. Shahrestani M, Yao R, Luo Z, et al. A field study of urban microclimates in London[J]. Renewable Energy, 2015, 73(jan.):3-9.
28. Zhang A, Gao C, Ling Z. Numerical simulation of the wind field around different building arrangements[J]. Journal of Wind Engineering & Industrial Aerodynamics, 2005, 93(12):891-904.
29. Li, M.W., 2016. The Study on Effect of Architecture Space Form on Wind Environment in Nanjing Residential District. MSC thesis. Southeast University, China.
30. Xi, R., 2017. Study on Residential Area Layout Based on Reasonable Silent Area. MSC thesis. Chongqing University, China.
31. Shui T, Liu J, Yuan Q, et al. Assessment of pedestrian-level wind conditions in severe cold regions of China[J]. Building & Environment, 2018, 135:53-67.
32. JGJ 286-2013,Design standard for thermal environment of urban residential areas[s].
33. GB/T 50378-2019,Assessment standard for green building[s].

 

Amendment:

References

34. Ma T , Chen T. Classification and pedestrian-level wind environment assessment among Tianjin's residential area based on numerical simulation - ScienceDirect[J]. Urban Climate, 34.
35. Moonen P, Defraeye T,Dorer V, et al. Urban Physics: Effect of the micro-climate on comfort, health and energy demand[J]. Frontiers of Architectural Research, 2012, 1(003):197-228.
36. Niu J, Liu J, Lee T C, et al. A new method to assess spatial variations of outdoor thermal comfort: Onsite monitoring results and implications for precinct planning[J]. Building & Environment, 2015, 91:263-270.
37. Stathopoulos Pedestrian level winds and outdoor human comfort[J]. Journal of Wind Engineering & Industrial Aerodynamics, 2006, 94(11):769-780.
38. BBlocken, TStathopoulos, Beeck J. Pedestrian-level wind conditions around buildings:Review of wind-tunnel and CFD techniques and their accuracy for wind comfort assessment[J]. Building Energy Efficiency, 2016.
39. Iqbal Q, Chan A L S. Pedestrian level wind environment assessment around group of high-rise cross-shaped buildings: Effect of building shape, separation and orientation[J]. Building & Environment, 2016, 101(may):45-63.
40. Lawson T V, Penwar De N A D. The effects of wind on people in the vicinity of buildings. 1975.
41. Ai Z T, Mak C M. CFD simulation of flow in a long street canyon under a perpendicular wind direction: Evaluation of three computational settings[J]. Building and Environment, 2017, 114:293-306.
42. Yang J ,  Yang Y ,  Sun D , et al. Influence of urban morphological characteristics on thermal environment[J]. Sustainable Cities and Society, 2021.
43. Luo X ,  Yang J ,  Sun W , et al. Suitability of human settlements in mountainous areas from the perspective of ventilation: A case study of the main urban area of Chongqing[J]. Journal of Cleaner Production, 2021:127467.
44. Yang J ,  Wang Y ,  Xiu C , et al. Optimizing local climate zones to mitigate urban heat island effect in human settlements[J]. Journal of Cleaner Production, 2020:123767.
45. Wu Y, Niu J. Numerical study of inter-building dispersion in residential environments: Prediction methods evaluation and infectious risk assessment[J]. Building & Environment, 2017, 115:199-214.
46. Yang X, Zhao L, Bruse M, et al. APPLICATION OF URBAN MICROCLIMATE SIMULATION DATA IN ASSESSING BUILDING ENERGY CONSUMPTION[J]. Acta Energiae Solaris Sinica, 2015, 36(6):1344-1351.
47. Hong B, Lin B, Lin J. Quantification of residential design parameters' effects on the outdoor wind environment using orthogonal experimental design (OED) and numerical simulation[J]. Procedia Engineering, 2017, 205:137-144.
48. Zhang X, Tse K T, Weerasuriya A U, et al. Evaluation of pedestrian wind comfort near 'lift-up' buildings with different aspect ratios and central core modifications[J]. Building & Environment, 2017, 124:245-257.
49. Wu H, Kriksic F. Designing for pedestrian comfort in response to local climate[J]. Journal of Wind Engineering and Industrial Aerodynamics, 2012, s 104–106(3):397-407.
50. An K, Fung J, Yim S. Sensitivity of inflow boundary conditions on downstream wind and turbulence profiles through building obstacles using a CFD approach[J]. Journal of Wind Engineering & Industrial Aerodynamics, 2013, 115(4):137-149.
51. GB 50176-2016, Code for thermal design of civil building[s].
52. Liu Z , Zhao X , Y Jin, et al. Prediction of Outdoor Human Thermal Sensation at the Pedestrian Level in High-rise Residential Areas in Severe Cold Regions of China[J]. Energy Procedia, 2019, 157:51-58.
53. Jin H ,  Liu S ,  Kang J . The Thermal Comfort of Urban Pedestrian Street in the Severe Cold Area of Northeast China[C]// Sustainability in Energy and Buildings 2017. 2017.
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55. Shui T , Liu J , Yuan Q , et al. Assessment of pedestrian-level wind conditions in severe cold regions of China[J]. Building & Environment, 2018, 135:53-67.
56. Capeluto I G, Yezioro A, Shaviv E . Climatic aspects in urban design—a case study[J]. Building & Environment, 2003, 38(6):827-835.
57. Allegrini J, Carmeliet J. Coupled CFD and building energy simulations for studying the impacts of building height topology and buoyancy on local urban microclimates[J]. Urban Climate, 2017, 21.
58. Stathopoulos T. Wind environmental conditions around tall buildings with chamfered corners[J]. Journal of Wind Engineering & Industrial Aerodynamics, 1985, 21(1):71-87.
59. Ng E, Chao Y, Liang C, et al. Improving the wind environment in high-density cities by understanding urban morphology and surface roughness: A study in Hong Kong[J]. Landscape & Urban Planning, 2011, 101(1):59-74.
60. Bo H, Lin B. Numerical studies of the outdoor wind environment and thermal comfort at pedestrian level in housing blocks with different building layout patterns and trees arrangement[J]. Renewable Energy, 2015, 73(jan.):18-27.
61. Emmanuel, Rohinton M . An Urban Approach To Climate Sensitive Design[M]. 2005.
62. Bonan G B. The microclimates of a suburban Colorado (USA) landscape and implications for planning and design[J]. Landscape and Urban Planning, 2000.
63. Kantzioura A, Kosmopoulos P, Zoras S . Urban surface temperature and microclimate measurements in Thessaloniki[J]. Energy and Buildings, 2012, 44(Jan.):63-72.
64. Kubota T, Miura M, Tominaga Y, et al. Wind tunnel tests on the relationship between building density and pedestrian-level wind velocity: Development of guidelines for realizing acceptable wind environment in residential neighborhoods[J]. Building & Environment, 2008, 43(10):1699-1708.
65. Taleghani M, Kleerekoper L, Tenpierik M, et al. Outdoor thermal comfort within five different urban forms in the Netherlands[J]. Building & Environment, 2015, 83(jan.):65-78.
66. Shahrestani M, Yao R, Luo Z, et al. A field study of urban microclimates in London[J]. Renewable Energy, 2015, 73(jan.):3-9.
67. Zhang A, Gao C, Ling Z. Numerical simulation of the wind field around different building arrangements[J]. Journal of Wind Engineering & Industrial Aerodynamics, 2005, 93(12):891-904.
68. Li, M.W., 2016. The Study on Effect of Architecture Space Form on Wind Environment in Nanjing Residential District. MSC thesis. Southeast University, China.
69. Xi, R., 2017. Study on Residential Area Layout Based on Reasonable Silent Area. MSC thesis. Chongqing University, China.
70. JGJ 286-2013,Design standard for thermal environment of urban residential areas[s].
71. GB/T 50378-2019,Assessment standard for green building[s].
72. Architectural Design Data Set of China.［M］.Beijing. 2017.
73. Franke, A. Hellsten, H. Schlünzen, et al., The COST 732 Best Practice Guidelinefor CFD simulation of flows in the urban environment: a summary, Int. J. Environ.Pollut. 44 (2011) 419–427, http://dx.doi.org/10.1504/ijep.2011.038443.
74. Tominaga, A. Mochida, R. Yoshie, et al., AIJ guidelines for practical applicationsof CFD to pedestrian wind environment around buildings, J. Wind Eng. Ind. Aerod.96 (2008) 1749–1761, http://dx.doi.org/10.1016/j.jweia.2008.02.058. 
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76. DB11 /938-2012 Standard for Green Building Design (Beijing)[s].
77. Mittal H , Sharma A , Gairola A . A review on the study of urban wind at the pedestrian level around buildings[J]. Journal of Building Engineering, 2018:S2352710217307581.

 

 

Point 6:There is some typing mistakes (e.g. Shrenyang, space between words, etc.). Please check carefully.

Response 7: Thank you very much for referees’ reports. We have modified the paper according to the review, and corrected the above mistakes.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The revision addressed most of my comments and suggestions. However, the authors should check the grammatical issues carefully and make sure that the grammar and expressions are of a high standard for publication.

Author Response

Thank you very much for giving us an opportunity to revise our manuscript. We have tried our best to revise our manuscript according to the comments. The language of this manuscript has been edited by a native English speaker. Attached please find the revised version, which we would like to submit for your kind consideration.

Author Response File: Author Response.docx

Reviewer 3 Report

I still don't think the paper has had the substantial changes in methodology and setup that are required for this to become worthy of publication. Seem y previous review for the issues, that can't simply be fixed by some restructuring and rewriting. I applaud the effort of the authors, but resubmission after a thorough reconsideration of the study at hand would seem the wiser choice.

Author Response

Thank you very much for your comments. We will try our best to revise the manuscript.

Author Response File: Author Response.docx