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Article

Surface Roughness Characteristics and Their Influence on Wind Erosion and Sand Movement

by
Jie Zhou
1,
Beibei Han
2,* and
Haifeng Wang
1
1
Key Laboratory of Ecological Safety and Sustainable Development in Arid Regions, National Engineering Technology Research Center for Desert-Oasis Ecological Construction, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
2
College of Resources and Environment, Xinjiang Agricultural University, Urumqi 830052, China
*
Author to whom correspondence should be addressed.
Atmosphere 2025, 16(4), 443; https://doi.org/10.3390/atmos16040443
Submission received: 27 February 2025 / Revised: 4 April 2025 / Accepted: 8 April 2025 / Published: 10 April 2025
(This article belongs to the Section Meteorology)
Browse Figures
Versions Notes

Abstract

:
Wind erosion significantly threatens sustainable development in desert regions, causing severe soil degradation. Investigating the influence of roughness elements on wind–sand interactions is vital for devising effective wind erosion control strategies. This study examined the effects of smooth and porous surface roughness elements on wind–sand activity and the wind erosion rate of a sand bed surface. Wind tunnel experiments were conducted with 10% coverage of these elements on the sand bed surface under varying wind speeds. Results showed that porous-surfaced roughness elements were less responsive to wind speed than smooth-surfaced spherical elements, significantly slowing wind erosion and enhancing sand bed stability. The porous-surfaced elements significantly reduced wind erosion rates by 21.8% at low wind speeds (8 m/s) and 18.23% at high wind speeds (14 m/s), compared to smooth-surfaced elements. The porous-surfaced spherical roughness elements effectively reduced the secondary lifting of sand particles by increasing the specific surface area, thereby improving the bed surface’s wind erosion resistance. These findings provide critical insights for optimizing sand control materials and developing more effective wind erosion mitigation strategies, offering a valuable reference for combating desertification.

1. Introduction

Wind erosion, a fundamental process in surface geomorphology evolution, significantly affects the ecological environment and agricultural production in arid and semi-arid regions. Wind erosion leads to a decline in soil fertility and triggers natural disasters, such as sand and dust storms, which cause significant human and socio-economic losses. Hence, researching preventative measures and control strategies for soil wind erosion is crucial for safeguarding the ecological environment and promoting sustainable development [1,2]. Two essential conditions must be met for soil wind erosion [2]: the presence of wind-erodible particles on the surface and adequate wind speed to mobilize these particles. Therefore, enhancing the structure of the soil surface and reducing near-surface wind speeds are key strategies for mitigating soil wind erosion.
Currently, extensive research has been undertaken by scholars regarding soil wind erosion [3,4]. The prevalent preventive and control measures encompass biological approaches (e.g., afforestation, microbial sand fixation, etc.), chemical methods (e.g., application of sand fixatives, etc.), and physical techniques (e.g., gravel mulching, establishment of grasslands, etc.). Although the implementation of physical [5,6,7,8], chemical [9,10], and biological sand fixation [11,12,13] measures has yielded notable results in curbing soil wind erosion, challenges persist, including complexities in construction, prohibitive costs, and the potential environmental pollution associated with chemical sand fixation [9]. Furthermore, mobile desert regions are characterized by a scarcity of natural sand control materials, and the expense involved in transporting sand control materials from external sources remains substantial. Meanwhile, biological sand control materials remain primarily confined to foundational theoretical research, with large-scale applications for sand control still in their infancy. As such, natural and biomass sand control materials continue to serve as the primary resources for sand mitigation efforts.
Researchers are actively evaluating gravel’s efficacy as a surface cover to inhibit wind–sand movement. Applying gravel on the bed surface can diminish the interaction between the wind–sand flow and application, thereby safeguarding the underlying fine-grained materials and consequently curtailing surface wind erosion and the dispersal of sand and dust [7,14]. This approach can achieve significant effectiveness in preventing and controlling wind erosion. The method of gravel covering emerges as a potent sand control strategy in the arid regions of northwest China [15,16]. The aerodynamic roughness of a landscape plays a crucial role in modulating the distribution of atmospheric turbulent momentum between rough elements and the substrate, as well as in the initiation and jump flux of sand particles and the resultant release of dust [17]. Previous research has indicated that the drag coefficient of gravel significantly impacts the suppression of wind and sand activities over the Gobi surface and that this coefficient tends to increase with both grain size and the extent of gravel coverage [18].
Prior studies have elucidated the optimal degree of coverage for gravel in wind erosion prevention methodologies, alongside the influence of rough elements’ geometric features on the bed’s aerodynamic properties (e.g., roughness, wind speed contours), viewed through the lens of wind and sand physics. However, investigations integrating the surface characteristics of roughness elements into sand prevention experiments remain scant [14,19,20]. In conclusion, variations in the geometric scales of roughness elements can further modulate wind–sand dynamics on the underlying bed by altering the aerodynamic roughness and the gravel drag coefficient [17,21,22]. While previous research has mainly focused on the impacts of factors such as scale and coverage of roughness elements on bed wind–sand activity [14,15,23,24,25], less attention has been devoted to understanding how the surface characteristics of these elements influence wind–sand interactions at the substrate.
This study aims to investigate the mechanisms by which the surface structural characteristics of roughness elements influence wind–sand activities on the overlay surface. By providing a theoretical basis for optimizing sand control materials, this research seeks to reduce construction complexity, costs, and environmental pollution risks. Additionally, the findings will offer scientific guidance for sand prevention and control in mobile desert areas, contributing to improved ecological environments and sustainable development. The results of this study will introduce innovative strategies for mitigating soil wind erosion, with significant implications for ecological restoration, environmental protection, and agricultural sustainability in arid and semi-arid regions.

2. Materials and Methods

2.1. Experimental Design

The wind tunnel used for the experiments was located at the Mosuowan Desert Research Station, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences (Figure 1). The wind tunnel was an indoor direct-current blowing wind tunnel, with an experimental section of 1.3 m × 1.0 m and a 16 m length, and the experimental wind speed of 5~20 ms−1 was continuously adjustable [26]. The net wind was selected for the experiment. Four groups of free wind speeds (8 ms−1, 10 ms−1, 12 ms−1, and 14 ms−1) were chosen to collect sand transported by wind–sand flows using a sand table (20 cm high, consisting of 1 cm × 1 cm sand inlets), with collection times of 10, 5, 3, and 2 min, respectively.
The experimental sand samples were collected from the surface of the shifting dunes of the Taklimakan Desert in the center of the Tarim Basin, Xinjiang Uygur Autonomous Region, China (39°05′99″ N, 83°64′04″ E), and fine and very fine sands dominated the mechanical composition. Particle size distribution (Figure 2) was analyzed by a laser particle size analyzer (Malveren MS-2000, Brighton, UK). The mineral composition of the sand was dominated by quartz, which accounted for 32.89%.
Two experimental models were selected: spherical rough elements with smooth surfaces and porous surfaces on the sand bed. The models were made in the laboratory and by hand using Quaternary red clay (See Figure 3). An equal mass of clay was weighed to shape it, and the shape was porous spherical, with 2 mm diameter steel needle drilling holes and a drilling depth of about 3 mm. Each rough element drilled 40 holes, with the drilling shape being approximately a cone. Finally, the model was placed in a dry and ventilated place to dry naturally. After drying, the mass (m), height (h), and diameter (d) of the model were weighed.
The vertical projection of particles method was used to calculate the coverage (Gd) of roughness elements in the sand bed. This method involved calculating Gd = Sb/C × 100%, where Sb is the vertical projection of the rough elements on the sand surface and C is the area of the sand table. In this experiment, the coverage of roughness elements was set to 10% to ensure weak interaction between models.
The experimental sand table used was rectangular and measured 4 cm in length, 35 cm in width, and 5 cm in depth. It was filled with experimental sand and scraped flat. Roughness elements were then randomly placed on the sand surface to maintain a uniform distribution. The number of smooth-surfaced spherical and porous-surfaced spherical roughness elements placed on each sand table under 10% coverage was 176, respectively.
A hole was cut in the bottom plate in the center of the test section to place the sand table in the wind tunnel. This ensured that the top edge of the sand table was flush with the bottom plate. Two stepped sand collectors were placed 50 cm downwind of the sand table (Figure 4).

2.2. Wind Erosion Rate

Wind speed was measured by a hot-wire anemometer in the front of the experimental section at a distance of 40 cm from the side wall (See Figure 4), and the experimental wind speeds were selected as 8, 10, 12, and 14 ms−1, with blowing erosion times of 10, 5, 3, and 2 min, respectively. The blowing erosion material deposited in the diffusion section of the wind tunnel was collected, and the wind erosion volume (Wd; kg) was determined by weighing with a 1/100 electronic balance. The wind erosion rate (Rd; kg cm−2 min−1) was defined as the amount of wind erosion per unit area per unit time. It was calculated according to the following equation:
Rd = Wd/(S × T),
where T is the blowing time (min), and S is the sand table area (cm2).

2.3. Sand Flux Profile

The sand flux profile was used to measure the amount of sand transported in a specified layer of airflow. It was calculated as the amount of transported sand per unit width perpendicular to the blow direction and per unit time:
qz = q0 exp(−kz),
where qz is the mass transport of sand at vertical height z (cm), q0 is the creep mass (g cm−2 s−1) transport of the sand at the surface (z = 0), and k is the decay factor.

2.4. Specific Surface Area

Specific surface area was the surface area per unit mass of a porous solid in cm2 g−1, calculated as the ratio of the surface area of a model to its mass [27]. For a porous spherical rough element, its specific surface area S was calculated as:
S = Sf/m,
where S is the specific surface area of porous-surfaced spherical roughness elements, Sf is the surface area of the porous-surfaced spherical roughness element, and m is the mass of the porous-surfaced spherical roughness elements.
The porous-surfaced spherical roughness elements area Sf consisted of a smooth spherical surface area S1 and the surface areas with 40 removed holes S2, with a diameter of d2 (2 mm) and a conical inner surface area S3:
Sf = S1 − S2 + S3
The smooth-surfaced spherical roughness elements surface area S1 was as follows, where d1 (1 cm) is the spherical roughness element diameter:
S1 = 4π(d1/2)2
S2 is the surface area of 40 holes with a diameter of d2 (2 mm), which was calculated as follows:
S2 = π(d1/2)2 × 40
The porous-surfaced spherical roughness element had a surface drilled to a depth of 3 mm (R) and a diameter of d2 (2 mm), the inner surface of which was approximately conical, and the conical inner surface can be viewed as a sector surface. The inner surface area of such a conical was:
S3 = LR/2 × 40
The arc length L of the sector was the circumference of a circle of the diameter d2 (3 mm), which was calculated as follows:
L = 2π(d2/2)

3. Results and Discussion

3.1. Effect of Smooth-Surfaced Spherical and Porous-Surfaced Spherical Roughness Elements on Bed Wind Erosion Rates

Table 1 shows the measured wind erosion amount and the wind erosion rate calculated according to Equation (1) for the smooth-surfaced spherical and porous-surfaced spherical roughness elements of the sand bed surface at 10% coverage under different wind conditions. From Table 1, it can be seen that wind speed was a direct factor affecting the amount and rate of wind erosion on the sand bed surface. Wind erosion occurred for both smooth-surfaced spherical and porous-surfaced spherical roughness elements under 10% coverage. However, wind erosion on smooth-surfaced spherical roughness elements increased as the wind speed increased. In contrast, porous-surfaced spherical roughness elements showed greater resistance to wind erosion, resulting in a much smaller increase in the erosion rate. This result indicates that having a porous surface structure can effectively slow down the wind erosion process and improve the stability of the sand bed.
The wind erosion rate of the porous-surfaced spherical roughness elements was lower than that of the smooth-surfaced spherical roughness elements under each wind speed condition (8, 10, 12, and 14 ms−1), which were 78.32%, 68.59%, 70.125%, and 81.87% of the smooth-surfaced spherical roughness elements, respectively. At the same time, the wind erosion amount of the porous-surfaced spherical roughness elements was relatively small under each wind condition, which were 80.03%, 77.53%, 72.55%, and 80.20% of the smooth-surfaced spherical roughness elements, respectively. This indicates that the surface porous structure can effectively slow down the wind erosion effect and reduce the amount and rate of wind erosion, which provides an essential reference for wind and sand stabilization. In addition, the pore structure can also help retain some sand particles and reduce the sand particles’ flying, which further reduces the wind erosion effect.
As can be seen in Figure 5, the wind erosion rate increased with increasing wind speed for both smooth-surfaced spherical and porous-surfaced spherical rough element-covered beds. The slope of the wind erosion rate versus the wind speed curve reflected the effect of the roughness element-covered surface on the wind erosion rate. The slope of the wind erosion rate curve of the smooth-surfaced spherical roughness element covering the bed significantly changed with the wind speed increase, and the slope value reached 0.9991. At the same time, the slope value of the porous-surfaced spherical roughness element also reached 0.9296, which indicated that the wind speed was a direct factor affecting the change in the wind erosion rate of the bed, and the wind erosion rate of the bed covered by the smooth-surfaced spherical roughness elements on the surface had a more significant response to the change in the wind speed. The steeper slope for smooth-surfaced roughness elements indicated a more pronounced impact on wind erosion, whereas the gentler slope for porous-surfaced roughness elements suggested a mitigating effect. The widening disparity of the slope indicated that porous surfaces can significantly reduce the migration of aeolian sand, especially under intense wind conditions.
This trend reflected the significance of the roughness element’s surface characteristics in controlling wind erosion, highlighting the potential of porous surfaces in wind erosion protection. Further analysis revealed that the difference in erosion rates between smooth- and porous-surfaced roughness elements became more pronounced at higher wind speeds. This suggests that porous surfaces are particularly effective in high-wind environments, where wind erosion is most severe.

3.2. Vertical Profile of Horizontal Mass Flux Between Smooth-Surfaced Spherical and Porous-Surfaced Spherical Roughness Elements at Varying Wind Speeds

As shown in Figure 6, the sand transport rates of the smooth-surfaced and porous-surfaced spherical roughness elements-covered sand bed surfaces were different, and both decreased with an exponential law and increased with the increase in wind speed. The sand transport rates of smooth-surfaced and porous-surfaced spherical roughness elements at a 1 cm height under wind speeds of 8, 10, 12, and 14 ms−1 were 1.856, 4.171, 5.818, and 6.696 g cm−2 min−1 and 1.069, 2.261, 3.591, and 5.25 g cm−2 min−1, respectively. It can be concluded that the transport rate of smooth-surfaced spherical roughness elements is greater than that of porous-surfaced spherical roughness elements.
The sand transport rates of smooth-surfaced and porous-surfaced spherical roughness elements were 0.021, 0.043, 0.076, and 0.122 g cm−2 min−1 and 0.008, 0.039, 0.063, and 0.215 g cm−2 min−1 at a height of 8 cm at wind speeds of 8, 10, 12, and 14 ms−1, respectively, which suggests that the porous spherical surface characteristics can, to some extent, more effectively inhibit the movement of sand particles and reduce wind–sand erosion. As for the smooth spherical roughness elements, despite less sand activity at lower wind speeds (8 and 10 ms−1), the sand transport rate increased significantly with increasing wind speeds (12 and 14 ms−1). This suggests that smooth-surfaced spherical elements may not be effective enough to suppress sand activity at high wind speeds, possibly because smooth surfaces do not efficiently disperse wind energy, resulting in sand grains being carried away more easily by the wind.
Many field and wind tunnel studies have also found an exponential relationship between sand transport fluxes and height variation [13,14,15,23,25]. As shown in Table 2, regression analysis showed that the decay curves of sand transport fluxes at the sand bed surface with smooth-surfaced spherical and porous-surfaced spherical roughness elements that were mulched can be expressed by an exponential equation (Equation (2)). Our study’s correlation coefficient, R2 ⫺ 0.94, was consistent with previous studies.
Sand transport increased with increasing wind speed. For example, in the bed covered with smooth-surfaced spherical roughness elements, the sand transport flux under 8 ms−1 was 2.826 g cm−2 s−1, and it reached 12.314 g cm−2 s−1 under 14 ms−1, which is almost about 4 times that under 8 ms−1. In the bed covered with porous-surfaced spherical roughness elements, the sand transport flux at 8 ms−1 was 4.204 g cm−2 s−1, and it reached 27.081 g cm−2 s−1 at 14 ms−1, which is almost 7 times higher than that at 8 ms−1. This shows that the wind speed is an essential factor affecting the sand transport flux on the bed. However, at the same wind speed, the sand transport fluxes were also significantly different, due to the differences in surface characteristics of smooth- and porous-surfaced spherical roughness elements. At a wind speed of 14 ms−1, the sand transport fluxes of the bed covered by smooth-surfaced spherical roughness elements were more than twice that of the porous-surfaced spherical roughness elements (smooth-surfaced spherical: 27.081 g cm−2 s−1, porous-surfaced spherical: 12.314 g cm−2 s−1). The pore structure of rough meta-surfaces influenced the airflow, thereby modifying the wind dynamics. Pores on a surface reduced the direct impact of the wind, limiting the potential for sand particles to be transported.

3.3. Effect of Spherical Roughness Elements’ Specific Surface Area on Sand Transport

As shown in Table 3, the specific surface area of the porous-surfaced spherical roughness elements increased from 3.14 cm2 to 9.42 cm2 (Equation (4)), and the specific surface area increased from 1.36 cm2 g−1 to 4.02 cm2 g−1 (Equation (3)), compared to the smooth-surfaced spherical roughness elements. The influence of the specific surface area on gaseous flow through a bed of coarse grains showed that fluid flow and surface interaction depended on the specific surface area [28]. This increased specific surface area significantly enhanced the opportunity for sand contact with the rough elements, which, in turn, enhanced the adsorption and reaction efficiency of the fluid and optimized the overall stability of the sand-covered bed surface. This optimization not only improved the filtration effect of the sand particles on the roughness element-covered bed but also reduced the fluid resistance and improved the overall sand fixation capacity.
As shown in Figure 6, the porous-surfaced spherical roughness elements showed stronger wind erosion resistance at higher wind speeds, and their structural properties helped form a stable sand bed protective layer, further slowing down the initiation and transport processes of sand particles and enhancing the durability of the bed. Smooth-surface roughness elements had weaker wind erosion resistance under the same wind speed conditions, and sand particles were easy to be initiated and transported faster, resulting in poorer bed stability and difficulty in forming a durable protective layer. By increasing the specific surface area, the porous spherical roughness effectively reduced the secondary lifting effect of sand particles, improved the wind erosion resistance of the bed surface, prolonged the stability period of the protective layer of the sand bed, and provided a more reliable solution for desertification control.
At the same time, the reduction of wind erosion can also extend the service life of the bed roughness element. The experimental results provide a new design idea and optimization direction for the wind and sand control project, which helps to improve the project efficiency and reduce the maintenance cost. In the future, further optimization of the porous structure parameters (porosity and distribution) of the roughness elements can further increase their specific surface area, which can further enhance the performance of fluid adsorption and wind erosion resistance and provide more optimal technical support for desertification control. The next step is to focus on the specific effects of the porous structure parameters on the fluid dynamics and to quantify the relationship between porosity and distribution on the resistance to wind–sand flow in order to achieve a more accurate design of wind and sand control.

4. Discussion

Wind tunnel simulation studies demonstrate that the shape of gravel significantly influences the bed surface characteristics and wind–sand dynamics processes. Specifically, the vertical wind speed profiles over angular gravel beds and smooth pebble beds both follow a logarithmic distribution. However, the rate of wind speed attenuation over angular gravel beds is significantly higher than over smooth cobble beds. Additionally, the dynamic roughness of angular gravel beds increases with wind speed, whereas the opposite trend is observed for cobble beds [19,22]. Fan et al. [20] pointed out that under the same coverage, the wind erosion rate of quicksand bed surfaces is affected by the geometry of roughness elements. The protection benefit of fine and high-shape roughness elements is better than that of coarse and short roughness elements. This is mainly because the drag coefficient of the bed covered by fine and high-shape roughness elements is more significant than that of wide and short shapes. It can be concluded that the optimization of the geometry of the roughness element is an effective method of mitigating wind erosion, thereby enhancing the stability of quicksand bed surfaces. It has been demonstrated that fine, tall elements disrupt airflow more efficiently, reducing erosion rates, compared to their coarse, short counterparts. This finding underscores the importance of selecting appropriate roughness elements for effectively implementing erosion control strategies. Further research suggests that these roughness elements’ spatial distribution and arrangement are crucial in maximizing erosion protection. Therefore, placing these roughness elements in place is a paramount defense, aiming to ensure optimal coverage and thus minimize gaps, which could otherwise allow wind erosion. The uniform distribution of elements enhances overall resistance, while varied arrangements adapt to local wind patterns, further bolstering defense mechanisms.
The surface has a smaller spacing, and the peaks and valleys comprise microscopic geometric features known as surface roughness. The smaller the surface roughness, the smoother the surface. Cao et al. [29] showed that when the inlet and outlet pressures are constant, the surface roughness has little effect on the pressure of the flow field. Still, the impact on the velocity field is significant, and the surface roughness reduces the flow velocity. Surface roughness increases the friction between the sand particles and the surface, making it more difficult for the sand particles to be moved when subjected to wind forces [30]. Thus, roughness increases the critical wind speed required for startup by increasing the friction coefficient.
Due to its special surface characteristics, the porous-surfaced spherical rough element had a larger surface roughness than the smooth-surfaced spherical rough element in this experiment, and its effect on the wind momentum at the surface was more obvious. This phenomenon suggests that increasing the roughness elements of surface textures can significantly enhance wind erosion resistance, offering valuable insights for designing sand fixation materials in environments prone to wind erosion.
The shape characteristics of roughness elements affect the wind distribution of surface shear force and wind momentum absorption [31]. A surface’s geometry, including depressions, angles, and protrusions, influences the direction and degree of turbulence within a flowing air stream. These geometric characteristics can change the airflow direction and increase localized pressures, contributing to a higher threshold for sand initiation and resulting in differences in the wind erosion resistance effect of different shapes of rough elements. Mei et al. [19], through a quantitative study of aerodynamic behavior, showed that the gravel resistance coefficient is also an essential factor affecting the inhibition of wind and sand activities on the Gobi bed, increasing with the grain size and cover of the gravel. Marshall et al. [32] analyzed the bed covered by roughness elements of different shapes and densities. They concluded that the drag coefficient of the bed covered by fine and tall-shaped roughness elements with obvious boundaries is more significant than that of wide and short-shaped roughness elements, which leads to the difference in wind–sand activity on the bed covered by roughness elements of different shapes. The shape characteristics directly affect the surface size of the roughness elements, affecting the absorption of wind momentum on the underlying bed.
An object moving through a fluid (gas or liquid) is subjected to fluid resistance. The drag force is different for objects with the same cross-section and different shapes facing the direction of the air stream. Liu et al. [33] showed that the air drag force is related to the shape of the object and the degree of surface smoothness, and the magnitude is proportional to the air drag coefficient and the windward area and also proportional to the square of the velocity. The porous-surfaced roughness elements have larger windward areas than the smooth-surfaced ones, resulting in a more significant drag force on the airflow and a larger shear force on the roughness elements. At the same time, the shear force acting on the bare ground is reduced, which is the main reason why the sand transport rate of the surface porous spherical roughness elements covering the sand bed is lower than that of the smooth spherical roughness elements. In addition, the porous spherical roughness element can effectively capture and retain wind and sand due to its complex surface characteristics, thus effectively slowing down the wind erosion process, protecting the sand bed stability, and reducing the bed wind erosion rate. In contrast, the smooth spherical roughness element has a smooth surface, and the sand particles easily collide with it to cause secondary impacts on the bed, exacerbating the lifting of sand particles.
Nickling and McKenna Neuman [34] showed that the intensity of wind–bed interaction is the main reason for the intensity of elastic collisions between sand particles and bed roughness elements, and the increase in elastic collisions is directly responsible for the rise in the sand transport rate. The porous-surfaced spherical roughness elements decrease the sand transport rate by increasing the specific surface area. In contrast, the smooth-surfaced spherical roughness elements elevate the sand material bouncing height by intensifying the wind–sand flow roughness element interaction activity.

5. Conclusions

Wind tunnel experiments were conducted to investigate the impact of smooth-surfaced spherical and porous-surfaced spherical roughness elements (10% coverage) on wind–sand activity and erosion rates under varying wind speeds.
The surface characteristics of porous-surfaced roughness elements significantly influenced the wind erosion rate and volume of the underlying bed by modulating the shear force of the airflow. Compared to smooth-surfaced spherical roughness elements, porous-surfaced spherical roughness elements demonstrated excellent resistance to wind erosion, enhancing bed stability. Specifically, they reduced the wind erosion rate by 21.8% and 18.23% and the erosion amount by 19.97% and 19.80% at low (8 ms−1) and high (14 ms−1) wind speeds, respectively.
The response of porous-surfaced spherical roughness elements to wind speed was notably lower than that of smooth spherical elements, which can more effectively inhibit the movement of sand particles and reduce wind–sand erosion. Under wind speeds of 8, 10, 12, and 14 ms−1, the sand transport rates at a height of 8 cm were 0.021, 0.043, 0.076, and 0.122 g cm−2 min−1 for smooth-surfaced spherical roughness elements and 0.008, 0.039, 0.063, and 0.215 g cm−2 min−1 for porous-surfaced spherical roughness elements. The smooth surfaces failed to disperse wind energy effectively, leading to easier sand transport. In contrast, porous-surfaced elements increased the specific surface area through a pore-like structure, enhancing friction between sand particles and the surface. This reduced the secondary impact of sand particles on the bed surface, improving wind erosion resistance and extending the stabilization period of the sand bed protection layer.
In summary, this study provided new design insights and optimization directions for wind and sand control projects. However, the wind tunnel experiments primarily focused on short-term effects, and practical wind erosion control strategies require long-term performance evaluation. Future research should address this limitation by investigating the stability and effectiveness of porous-surfaced spherical roughness elements during long-term field applications. Additionally, further work could explore the specific effects of porous structural parameters (e.g., porosity and distribution) on fluid dynamics, quantifying their relationship with wind and sand flow resistance. These efforts will contribute to more precise and sustainable designs for wind and sand control, enhancing the durability and efficiency of such projects.

Author Contributions

Conceptualization, J.Z., H.W. and B.H.; methodology, J.Z.; formal analysis, B.H.; investigation, H.W.; resources, H.W.; data curation, B.H.; writing—original draft preparation, J.Z.; writing—review and editing, J.Z.; supervision, H.W.; funding acquisition, B.H. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Major Science and Technology Projects of Xinjiang Uygur Autonomous Region (2022A02007-2-1).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Atmosphere 16 00443 g001
Figure 1. The wind tunnel laboratory.
Figure 1. The wind tunnel laboratory.
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Figure 2. (a) Particle size distribution, (b) mineralogical composition, and sand micro-morphology (magnification: ×100).
Figure 2. (a) Particle size distribution, (b) mineralogical composition, and sand micro-morphology (magnification: ×100).
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Figure 3. Spherical roughness elements with porous-surfaced elements.
Figure 3. Spherical roughness elements with porous-surfaced elements.
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Figure 4. The experimental layout.
Figure 4. The experimental layout.
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Figure 5. Relationship between wind erosion rates and wind speeds on beds covered with smooth-surfaced and porous-surfaced spherical roughness elements.
Figure 5. Relationship between wind erosion rates and wind speeds on beds covered with smooth-surfaced and porous-surfaced spherical roughness elements.
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Figure 6. Vertical profile of the mass flux horizontal with wind speed between smooth-surfaced spherical (a) and porous-surfaced spherical roughness elements (b).
Figure 6. Vertical profile of the mass flux horizontal with wind speed between smooth-surfaced spherical (a) and porous-surfaced spherical roughness elements (b).
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Table 1. Wind erosion amount and wind erosion rate for smooth-surfaced spherical and porous-surfaced spherical roughness elements at 10% coverage.
Table 1. Wind erosion amount and wind erosion rate for smooth-surfaced spherical and porous-surfaced spherical roughness elements at 10% coverage.
Wind Speed
(ms−1)		Testing Time
(min)		Roughness Element
Porous-Surfaced SphericalSmooth-Surfaced Spherical
Wd (kg)Rd (kg cm−2 min−1)Wd (kg)Rd (kg cm−2 min−1)
8100.9580.6181.1970.798
1051.2841.6561.8112.414
1231.3512.9011.8624.137
1421.5194.8971.8945.981
Table 2. The sand transport fluxes of smooth-surfaced and porous-surfaced spherical rough elements mulched to the bed at different velocities.
Table 2. The sand transport fluxes of smooth-surfaced and porous-surfaced spherical rough elements mulched to the bed at different velocities.
Spherical Roughness ElementsU (ms−1)Q (g cm−2 s−1)q0kR2
Porous-surfaced82.8262.5570.3680.997
107.9886.1730.3820.949
1211.2728.6890.4570.940
1412.3149.9350.4140.962
Smooth-surfaced84.2041.9090.4080.945
109.1394.5040.3040.949
1217.4276.2590.3080.966
1427.0819.2980.3780.971
For the fitted function Equation (2), qz is the sand transport rate at height z. U is wind velocity. Q is the total transport rate. q0 and k are regression coefficients. R2 is the squared correlation coefficient.
Table 3. Geometrical parameter characteristics of spherical roughness elements on single smooth-surfaced and porous-surfaced elements.
Table 3. Geometrical parameter characteristics of spherical roughness elements on single smooth-surfaced and porous-surfaced elements.
Spherical Roughness Elementsd (cm)Sf (cm2)m (g)S (cm2 g−1)
smooth-surfaced1.003.142.311.36
porous-surfaced1.019.422.314.02
Wd is the diameter of the roughness element (cm). m is the quantity of the roughness element (g). Sf is the surface area (cm2), and S is the specific surface area (cm−2 g−1).
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Zhou, J.; Han, B.; Wang, H. Surface Roughness Characteristics and Their Influence on Wind Erosion and Sand Movement. Atmosphere 2025, 16, 443. https://doi.org/10.3390/atmos16040443

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Zhou J, Han B, Wang H. Surface Roughness Characteristics and Their Influence on Wind Erosion and Sand Movement. Atmosphere. 2025; 16(4):443. https://doi.org/10.3390/atmos16040443

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Zhou, Jie, Beibei Han, and Haifeng Wang. 2025. "Surface Roughness Characteristics and Their Influence on Wind Erosion and Sand Movement" Atmosphere 16, no. 4: 443. https://doi.org/10.3390/atmos16040443

APA Style

Zhou, J., Han, B., & Wang, H. (2025). Surface Roughness Characteristics and Their Influence on Wind Erosion and Sand Movement. Atmosphere, 16(4), 443. https://doi.org/10.3390/atmos16040443

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