Characteristics of Turbulent Aeolian Sand Movement Over Straw Checkerboard Barriers and Formation Mechanisms of Their Internal Erosion Form

Abstract

Straw checkerboard barrier (SCB) array is one of the most effective and widely used measures for antidesertification projects. The efficiency and durability of SCB are greatly influenced by the features of wind field and sand particle motion. Unfortunately, very few studies have explored the characteristics of turbulent flow and the internal erosional form inside the barrier cell, because of the complexity of turbulent flow and the sand particle motion around the surface of SCBs. In this paper, we simulated the wind-sand flow around SCBs using 3-D hybrid Reynolds-averaged Navier-Stokes/large eddy simulation method and Lagrangian particle tracing method to analyze the characteristics of turbulent flow, particle motion, and internal erosional form of SCBs. The results show that the vast majority of particles fall into SCB cells from their middle and posterior parts when wind-sand flow passes SCBs, due to the impact of gravity and subsidence flow. It indicates that SCBs could effectively prevent sand flow-induced hazards. The turbulent flow in SCBs has great instantaneous pulse velocity, resulting in retransfer of sand particles in SCBs. Analysis of the mean flow field in SCB found one huge streamwise vortex that filled the SCB cells and two spanwise vortexes in the back of SCB cells. These vortexes will drive particles inside SCBs to move toward the front and side walls, making the erosional form of SCB cells low in the middle and high near all the sides.Plain Language Summary Straw checkerboard barrier (SCB) is the most representative anti-desertification measure and plays a significant role in anti-desertification projects. We studied the wind-sand flow around SCBs using computational method and analyzed the characteristics of turbulent flow, particle motion and internal erosional form of SCBs. Based on the simulation results, the weakness of current SCBs can be identified. Therefore, this research is of significance in improving artificial sand control measures designed to help combat desertification control.

CFD simulation of the wind field over a terrain with sand fences: Critical spacing for the wind shear velocity

“…The model by Xu et al (2018) is, thus, different from ours, since we investigate the structure of the flow without particles. It is, thus, not possible to apply the same technique proposed by Xu et al (2018) to validate the simulation predictions for vertical sand flux profile, since in our simulations we only investigated the structure of the turbulent wind free of saltating or suspended particles. Moreover, with regard to a verification of the wind profile alone (without particles), to the best of our knowledge, there is no experiment that investigates the turbulent flow profile using the same conditions as in our simulations.…”

“…In this context, we remark that Xu et al (2018) pioneered the study of the flow characteristics of turbulent aeolian sand over straw checkerboard barriers and the erosion-deposition patterns resulting from the interaction between particles, fluid and obstacles. In particular, these authors studied the flow over checkerboards by taking into account the motion of the particles, which disturb the wind profile (Xu et al, 2018). In their simulations, the checkerboards consisted of 10 cm high obstacles, and wind tunnel experiments were also performed using the same conditions as in the simulations to verify the predictions for wind velocity and sand flux (Xu et al, 2018).…”

“…In particular, these authors studied the flow over checkerboards by taking into account the motion of the particles, which disturb the wind profile (Xu et al, 2018). In their simulations, the checkerboards consisted of 10 cm high obstacles, and wind tunnel experiments were also performed using the same conditions as in the simulations to verify the predictions for wind velocity and sand flux (Xu et al, 2018). The model by Xu et al (2018) is, thus, different from ours, since we investigate the structure of the flow without particles.…”

“…In their simulations, the checkerboards consisted of 10 cm high obstacles, and wind tunnel experiments were also performed using the same conditions as in the simulations to verify the predictions for wind velocity and sand flux (Xu et al, 2018). The model by Xu et al (2018) is, thus, different from ours, since we investigate the structure of the flow without particles. It is, thus, not possible to apply the same technique proposed by Xu et al (2018) to validate the simulation predictions for vertical sand flux profile, since in our simulations we only investigated the structure of the turbulent wind free of saltating or suspended particles.…”

“…However, we remark that an interesting point for future work is the investigation of how different meshes affect surface roughness and flow convergence. Such an investigation could be conducted, for instance, by explicitly accounting for mesh elements at the inlet, such as in previous wind tunnel experiments (Xu et al, 2018).…”