Fire | Special Issue : Dynamics of Wind-Fire Interaction: Fundamentals and Applications

Research

22 pages, 15478 KiB

Open AccessArticle

Wind Effect on External Fire Spread through Openings under the Protection of Horizontal Projections or Vertical Spandrels—A Numerical Study

by Yining Tang, Zhaofeng Tian, Xiao Chen, Brigitta Suendermann, Grant Gamble and Zefeng Huang

Fire 2024, 7(3), 66; https://doi.org/10.3390/fire7030066 - 25 Feb 2024

Viewed by 1007

Abstract

A numerical investigation has been conducted to analyse the effect of wind on the vertical spread of fire through a front opening in a building’s external walls. The study utilises a building geometry established from previous experimental work conducted by the National Research [...] Read more.

A numerical investigation has been conducted to analyse the effect of wind on the vertical spread of fire through a front opening in a building’s external walls. The study utilises a building geometry established from previous experimental work conducted by the National Research Council of Canada (NRCC). A horizontal projection or a vertical spandrel is introduced above the opening of the compartment of fire origin. The purpose of the projection or spandrel is to inhibit the vertical spread of the fire, following the relevant requirements in the Australian National Construction Code (NCC). A computational fluid dynamics (CFD) package for fire-driven fluid flow, namely the Fire Dynamics Simulator (FDS), is employed to simulate the fire behaviour. The FDS model is validated against the NRCC’s experimental results, and a good agreement is achieved. Winds from three horizontal directions (front wind is normal to the opening, side wind is parallel to the opening, and back wind is from behind the building) have been investigated, with speeds ranging up to 10 m/s for each wind direction. Front wind speeds below 1 m/s are found to slightly enhance the vertical spread of the fire, while speeds exceeding 1 m/s are inclined to promote horizontal spread. The impact of side wind on the vertical fire spread was also found to vary with wind speed. The increase in the speed of back wind influences flame buoyancy, resulting in an augmented vertical fire spread. Furthermore, the numerical results reveal that a vertical spandrel of 1100 mm height is less effective in preventing vertical fire spread through openings, compared to a 1100 mm deep horizontal projection. The study suggests that the fire safety design in reducing the hazard of vertical fire spread through openings in buildings’ external walls could be further improved if the effect of wind is considered. Full article

(This article belongs to the Special Issue Dynamics of Wind-Fire Interaction: Fundamentals and Applications)

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19 pages, 5351 KiB

Open AccessArticle

Effect of Semi-Transverse Ventilation Velocity on Combustion Characteristics of Pool Fire Sources in a Scaled Tunnel

by Liyue Gong, Yifan Peng, Jun Xu, Wanli Li, Tianyao Jia, Junqiu Ma and Haihang Li

Fire 2024, 7(1), 18; https://doi.org/10.3390/fire7010018 - 04 Jan 2024

Cited by 1 | Viewed by 1297

Abstract

Compared to longitudinal ventilation, there are few studies on fire source development under semi-transverse ventilation. This work studied the influence of semi-transverse ventilation on the combustion characteristics of fire sources in a scaled tunnel. The burning rate and heat transfer feedback during pool [...] Read more.

Compared to longitudinal ventilation, there are few studies on fire source development under semi-transverse ventilation. This work studied the influence of semi-transverse ventilation on the combustion characteristics of fire sources in a scaled tunnel. The burning rate and heat transfer feedback during pool fire combustion were revealed under different longitudinal and transverse ventilation velocities. The results showed that transverse ventilation had little influence on combustion characteristics, and the burning rate was more obviously affected by longitudinal ventilation. The heat convection feedback increased monotonically with the increase of the longitudinal ventilation, which led to the increase of the total heat feedback on the fuel. The heat radiation feedback changed little, and the heat conduction feedback decreased monotonically with the increase of the longitudinal ventilation velocity. By aid of a Fire Dynamics Simulator, it was found that the flame tilted downstream and was in the flow line of the lower cold air flow coming from upstream and the upper hot smoke flow outgoing in the downstream direction. The transverse ventilation of 2 m/s or lower hardly affected the combustion field of the fire source. Therefore, semi-transverse ventilation is preferable to longitudinal ventilation from the point of view of limiting fire expansion. Full article

(This article belongs to the Special Issue Dynamics of Wind-Fire Interaction: Fundamentals and Applications)

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10 pages, 2196 KiB

Open AccessArticle

Empirical Evidence of Reduced Wildfire Ignition Risk in the Presence of Strong Winds

by Assaf Shmuel and Eyal Heifetz

Fire 2023, 6(9), 338; https://doi.org/10.3390/fire6090338 - 29 Aug 2023

Viewed by 1091

Abstract

Anyone who has tried lighting a campfire on a windy day can appreciate how difficult it could be. However, despite real-life experience and despite laboratory experiments which have demonstrated that fire ignition risk dramatically decreases beyond a certain wind threshold, current fire weather [...] Read more.

Anyone who has tried lighting a campfire on a windy day can appreciate how difficult it could be. However, despite real-life experience and despite laboratory experiments which have demonstrated that fire ignition risk dramatically decreases beyond a certain wind threshold, current fire weather indices (FWIs) do not take this effect into account and assume a monotonic relation between wind velocity and ignition risk. In this paper, we perform a global analysis which empirically quantifies the probability of ignition as a function of wind velocity. Using both traditional methods (a logistic regression and a generalized additive model) and machine learning techniques, we find that beyond a threshold of approximately 3–4 m/s, the ignition risk substantially decreases. The effect holds when accounting for additional factors such as temperature and relative humidity. We recommend updating FWIs to account for this issue. Full article

(This article belongs to the Special Issue Dynamics of Wind-Fire Interaction: Fundamentals and Applications)

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12 pages, 4584 KiB

Open AccessArticle

Experimental Investigation on the Impact of Varying Air-Inlet Widths and Fuel Pan Diameters on Fire Whirls’ Combustion Characteristics

by Chao Ding, Lingfeng He, Zijian Yan, Yuyao Li, Shuangyang Ma and Yan Jiao

Fire 2023, 6(8), 309; https://doi.org/10.3390/fire6080309 - 10 Aug 2023

Viewed by 1067

Abstract

A fire whirl, a unique fire behavior, occurs when a vertical vortex of flames skyrockets due to specific surrounding temperatures and thermal gradient conditions during a fire. Compared with conventional fire plumes, fire whirls exhibit a higher air entrainment rate, tangential velocity, and [...] Read more.

A fire whirl, a unique fire behavior, occurs when a vertical vortex of flames skyrockets due to specific surrounding temperatures and thermal gradient conditions during a fire. Compared with conventional fire plumes, fire whirls exhibit a higher air entrainment rate, tangential velocity, and axial velocity, thus presenting greater risks and destructive capabilities. Thus, studying the combustion characteristics of fire whirls becomes necessary. This experiment employed a small-scale, fixed-frame fire whirl generator. We investigated how varying air-inlet widths and fuel pan diameters influence the fire whirl’s combustion characteristics. Experimental images indicated a negative correlation between the fire whirl’s flame height and the air-inlet width, and a positive correlation with the fuel pan diameter. Our findings showed that the burning rate of the fire whirl during the quasi-steady-state combustion phase initially increased and then decreased as the air-inlet width expanded, peaking at a width of 7 cm. The data demonstrated a corresponding power-law relationship between the fire whirl’s dimensionless flame height and excess temperature. Ultimately, our results indicated a positive correlation between the 2/5 power of the fire whirl’s dimensionless heat release rate and the dimensionless flame height. The ratios of maximum to mean flame height and mean to continuous flame height are 1.35 and 1.5, respectively. Significantly, these ratios remain unaffected by the air-inlet width, fuel pan diameter, environmental temperature, and heat release rate. Full article

(This article belongs to the Special Issue Dynamics of Wind-Fire Interaction: Fundamentals and Applications)

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18 pages, 1358 KiB

Open AccessArticle

Comparative Assessment of Wildland Fire Rate of Spread Models: Effects of Wind Velocity

by Dionysios I. Kolaitis, Christos Pallikarakis and Maria A. Founti

Fire 2023, 6(5), 188; https://doi.org/10.3390/fire6050188 - 04 May 2023

Cited by 1 | Viewed by 1226

Abstract

Wildland fire rate of spread prediction models are important tools for the effective coordination of resident evacuation and fire suppression efforts. A comparative assessment of ten empirical and semi-empirical rate of spread prediction models is performed, using a selection of 203 laboratory experiments [...] Read more.

Wildland fire rate of spread prediction models are important tools for the effective coordination of resident evacuation and fire suppression efforts. A comparative assessment of ten empirical and semi-empirical rate of spread prediction models is performed, using a selection of 203 laboratory experiments of surface spreading fires; special emphasis is given to the effects of external wind velocity. Five of the evaluated models have been developed using measurements obtained in laboratory-scale tests; these models are combined with two supplementary sub-models that account for the effects of wind. In addition, a selection of five empirical models that have been developed using large-scale field tests are also assessed. The performance of the ten prediction models is evaluated, both qualitatively and quantitatively, by employing a range of statistical error metrics. The laboratory-developed models are found to exhibit high sensitivity on low fuel load values, when no external wind is present, as well as on low packing ratios and high wind velocity values. The field-developed models exhibit significant discrepancies against the experimental data, due to the use of specific parameters regarding fuel type, scale and wind velocity. Full article

(This article belongs to the Special Issue Dynamics of Wind-Fire Interaction: Fundamentals and Applications)

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12 pages, 6022 KiB

Open AccessArticle

Peatland Fire Weather Conditions in Central Kalimantan, Indonesia

by Aswin Usup and Hiroshi Hayasaka

Fire 2023, 6(5), 182; https://doi.org/10.3390/fire6050182 - 28 Apr 2023

Cited by 7 | Viewed by 1704

Abstract

Peatland fires in Central Kalimantan emit thick smoke and large amounts of greenhouse gases and have an impact on the environment globally, but studies on fire weather have not been carried out due to lack of diurnal weather data. The aim of this [...] Read more.

Peatland fires in Central Kalimantan emit thick smoke and large amounts of greenhouse gases and have an impact on the environment globally, but studies on fire weather have not been carried out due to lack of diurnal weather data. The aim of this study is to identify the fire weather conditions during active fires that is needed to mitigate future occurrences of peat fires in Indonesia. The available diurnal weather data was used to analyze the fire weather conditions. Based on meteorological data on active fires (11 days), there was a significant increase in air temperature due to the sea breeze that started blowing in the morning. The average values for the 11-day period around 15:00 are a maximum air temperature of 36 °C, minimum humidity of 37%, wind speed of 21 km h⁻¹, and a rate of increase of 2.7 °C h⁻¹ from 8:00. The difference in sea and land temperatures causes strong winds to blow and triggers an increase in land temperatures. The results of this report can help predict fire activity at high temperatures in the future based on global warming predictions made by other researchers. The rapid rate of increase in air temperature from the morning will be useful in anticipating fires in Central Indonesia. Full article

(This article belongs to the Special Issue Dynamics of Wind-Fire Interaction: Fundamentals and Applications)

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24 pages, 12478 KiB

Open AccessArticle

Convective Density Current Circulations That Modulated Meso-γ Surface Winds near the Yarnell Hill Fire

by Michael L. Kaplan, S. M. Shajedul Karim, Jackson T. Wiles, Curtis N. James, Yuh-Lang Lin and Justin Riley

Fire 2023, 6(4), 130; https://doi.org/10.3390/fire6040130 - 23 Mar 2023

Viewed by 1801

Abstract

On 30 June 2013, 19 Granite Mountain Hotshots firefighters were killed fighting a wildfire near Yarnell in the mountains of Central Arizona. They succumbed when the wildfire, driven by erratic winds, blocked their escape route and overran their location. A previous study is [...] Read more.

On 30 June 2013, 19 Granite Mountain Hotshots firefighters were killed fighting a wildfire near Yarnell in the mountains of Central Arizona. They succumbed when the wildfire, driven by erratic winds, blocked their escape route and overran their location. A previous study is extended to simulate and analyze the downscale organization of convective circulations that redirected the wildfire, which started from the scale of the Rossby Wave Breaking over North America to a convective gust front that redirected the wildfire, trapping the firefighters. Five stages are found: Stage I, the initial deep prolonged gust front; Stage II, a front-to-rear jet and its ascending motions that organized high-based convection; Stage III, high-based dry microburst-induced downdrafts organized initially by ascending flow in Stage II that transported mass and entropy to the surface; Stage IV; multiple meso-γ-scale high centers and confluence zones formed that encompassed the firefighters’ location, which established a favorable environment leading to Stage V, canyon-scale circulations formed surrounding the fire. The atmosphere thus transitioned from supporting a deep and long-lived convective density current to elevated dry microbursts with mass and wind outflow into a canyon, redirecting the ongoing wildfire. Full article

(This article belongs to the Special Issue Dynamics of Wind-Fire Interaction: Fundamentals and Applications)

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Review

Jump to: Research, Other

17 pages, 1492 KiB

Open AccessReview

Software-Based Simulations of Wildfire Spread and Wind-Fire Interaction

by Maryam Ghodrat, Farshad Shakeriaski, Sayyed Aboozar Fanaee and Albert Simeoni

Fire 2023, 6(1), 12; https://doi.org/10.3390/fire6010012 - 31 Dec 2022

Cited by 5 | Viewed by 4457

Abstract

Wildfires are complex phenomena, both in time and space, in ecosystems. The ability to understand wildfire dynamics and to predict the behaviour of the propagating fire is essential and at the same time a challenging practice. A common approach to investigate and predict [...] Read more.

Wildfires are complex phenomena, both in time and space, in ecosystems. The ability to understand wildfire dynamics and to predict the behaviour of the propagating fire is essential and at the same time a challenging practice. A common approach to investigate and predict such phenomena is making the most of power of numerical models and simulators. Improved and more accurate methods for simulating fire dynamics are indispensable to managing suppression plans and controlled burns, decreasing the fuel load and having a better assessment of wildfire risk mitigation methodologies. This paper is focused on the investigation of existing simulator models applicable in predicting wildfire spread and wind fire interaction. The available software packages are outlined with their broad range of applications in fire dynamic modeling. Significance of each work and associated shortcomings are critically reviewed. Finally, advanced simulations and designs, accurate assumptions, and considerations for improving the numerical simulations, existing knowledge gaps in scientific research and suggestions to achieve more efficient developments in this area are revisited. Full article

(This article belongs to the Special Issue Dynamics of Wind-Fire Interaction: Fundamentals and Applications)

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Other

Jump to: Research, Review

18 pages, 17225 KiB

Open AccessTechnical Note

It’s about Time: A Method for Estimating Wildfire Arrival and Weather Conditions at Field-Sampled Locations

by Angela M. Klock, Sebastian Busby and Jeremy S. Fried

Fire 2023, 6(9), 360; https://doi.org/10.3390/fire6090360 - 16 Sep 2023

Cited by 1 | Viewed by 1303

Abstract

Weather conditions at the time of wildfire front arrival strongly influence fire behavior and effects, yet few methods exist for estimating weather conditions more spatio-temporally resolved than coarse-grain (e.g., 4 km) daily averages. When a fire front advances rapidly and weather conditions are [...] Read more.

Weather conditions at the time of wildfire front arrival strongly influence fire behavior and effects, yet few methods exist for estimating weather conditions more spatio-temporally resolved than coarse-grain (e.g., 4 km) daily averages. When a fire front advances rapidly and weather conditions are heterogeneous over space and time, greater spatio-temporal precision is required to accurately link fire weather to observed fire effects. To identify the influence of fire weather on fire effects observed across a sample of existing forest inventory plots during a wind-driven megafire event in the US Pacific Northwest, we explored and compared three methods for estimating time of fire arrival and the wind speed at that arrival time for each plot location. Two methods were based on widely used, remotely sensed active fire data products with dissimilar spatial and temporal resolutions. The third and preferred method, Modeled-Weather Interpolated Perimeters (MoWIP), is a new approach that leveraged fine-grained (1.3 km, hourly) wind speed and direction from modeled fire weather to guide interpolation of aerial infrared-detected (IR) operational perimeters, subdividing the time intervals defined by sequential IR perimeters into quartile intervals to enhance temporal resolution of predicted fire arrival times. Our description of these fire arrival “time stamp” methods and discussion of their utility and shortcomings should prove useful to fire scientists, ecologists, land managers, and future analyses seeking to link estimated fire weather and observed fire effects. Full article

(This article belongs to the Special Issue Dynamics of Wind-Fire Interaction: Fundamentals and Applications)

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