Influence of sand size on motion and transport characteristics of wind-sand two-phase flow in desert environments

The influence of sand size on motion and transport characteristics of wind-sand two-phase flow is a crucial theoretical foundation for addressing global desertification issues. This study conducts a detailed investigation into the influence of sand size on air flow characteristics, sand motion behaviors, and transport distributions in the wind-sand two-phase flow using TFM method. The results indicate that the existence of sand particles decreases the air velocity, widens the air dynamic range and intensifies the momentum transfer process. When the sand size increases from 10 to 400 μm, the dynamic height and maximum turbulent kinetic energy decrease by 79.3 % and 82.1 %, respectively. The initial saltation velocities in the horizontal and vertical directions are predominantly distributed within the ranges of −0.1 to 0.7 m/s and 0–0.6 m/s, respectively. The initial horizontal and vertical saltation velocities corresponding to the peak proportion increase with decreasing sand size. The horizontal and vertical distributions of sediment transport flux conform to the exponential decline law, reflecting the magnitude, distribution and extent of sand transportation into the desert flow field. When the sand diameter rises from 100 to 400 μm, the maximum values of sediment transport flux in vertical and horizontal directions increase by 1.83 times and 1.01 times, respectively, while the transport indexes decrease by 5.6 % and 10.3 %, respectively. The variation characteristics of sediment transport range differ between low and high air friction velocities as sand size increases. These research findings provide important theoretical guidance for the control of desertification.