Simulation of aerodynamic entrainment of sand particles on an up-sloping bed using the discrete element method

Research on aerodynamic entrainment of sand particles on sloped beds can obtain natural wind-blown sand saltation patterns that are closer to real terrains. Therefore, a discrete element numerical model of the slope sand bed was constructed, and wind field with logarithmic profile along the bed surface was set up to reproduce the aerodynamic entrainment process of sand particles on a sloped surface. The simulation results show that compared with a flat bed, the entrainment rate decreases by nearly 90% when the slope angle of bed reaches 20°. Sand particles on a sloped bed need to accumulate more energy to be separated from the bed. Thus, they have to experience a longer rolling distance and more frequent collisions during the process of aerodynamic entrainment. • Inhibitory effect on aerodynamic entrainment increases noticeably with slope angle. • Slope raises threshold velocity by 50% and reduces entrainment rate by 90%. • Rolling distance and number of collisions increase by nearly 55% than that on flat. • Scheme for aerodynamic entrainment of sand on slope was summarized based on DEM. Aeolian sediment transport is the main cause of natural disasters such as dust storms and land degradation in arid and semi-arid regions, with aerodynamic entrainment being a key physical process. While most studies on aerodynamic entrainment focus on flat beds, the aerodynamic entrainment of sand particles on sloping beds remains underexplored. In this study, models of sand beds sloping at angles ranging from 0° to 20° were developed using the discrete element method, and the aerodynamic entrainment process on these beds was simulated. The results indicate that the inhibitory effect on aerodynamic entrainment increases considerably with slope angle. Compared to those for flat beds, the threshold friction velocity and response time of aerodynamic entrainment on sloping beds increase by approximately 50%, while the entrainment rate decreases by almost 90% at a slope angle of 20°. From a particle motion perspective, sand particles on a sloping bed require more energy to detach from the bed, resulting in an increase of almost 55% in rolling distance and number of collisions compared to that for a flat bed. In this study, an aerodynamic entrainment scheme for sloping beds was proposed, enhancing the understanding of wind-blown sand movement in real terrains and improving prediction accuracy.