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.