Simulation of aerodynamic entrainment with interparticle cohesions based on discrete element method

Abstract

AbstractAerodynamic entrainment acts as the pioneer of saltation movement and is critical for understanding the development of aeolian phenomena. In this study, air‐driven particles whose bottoms have left the bed surface were considered to be entrainment particles; this definition differs from the previous definition considering the initiation of rolling. We simulated the aerodynamic lifting of surface particles on a randomly oriented sedimentary bed using the discrete element method (DEM); we also proved that particles do not leave the bed vertically with speeds equal to the speed required to reach the height of one grain diameter, as is widely accepted. Rather, the particles were found to leave the bed at a much smaller angle and with much larger velocities with respect to the bed surface. The rate of entrainment exhibits an approximately linear dependence on the shear velocity, not a quadratic dependence, because the velocity of the entrained particles increases linearly with shear velocity. Moreover, the interparticle cohesion, which was found to increase the fluid entrainment threshold significantly, had no effect on the entrainment rate or on the take‐off velocity and angular distributions of the entrained particles. This is because the collisions between the entrained and bed particles destroy the interparticle bonds. Herein, we summarize a complete entrainment scheme based on DEM simulations, which provides a new approach for exploring the development and evolution of aeolian transportation processes.