The ejection pattern of sand particles in steady‐state aeolian transport

ABSTRACT Aeolian sediment transport reshapes planetary landscapes and causes various environmental problems. For almost a century, it has been broadly recognized that the features of ejection particles are dominated by each independent impact process. Using a coupled fluid‐discrete element model to resolve creeping and saltating motions simultaneously, we observed that, under steady‐state transport, almost all ejectors are evolved gradually from energetic creeping particles that were maintained by the combined action of fluid shear and continuous grain‐bed collisions, where the last effective impact before the particle is ejected into the air barely contributes to less than 20% of the total momentum on average. Furthermore, aeolian ejectors undergo several to tens of effective impacts prior to being ejected into the air, during which the momentum transferred from the impact particles is an order of magnitude higher than that from the fluid drag. Thus, ejected particles are mostly generated by a series of effective impacts rather than being dominated by a single impact. These findings pose a significant challenge to the existing ejection dynamics of wind‐blown sand movement. Largely, this is because the energetic creeping particles form a rheological layer atop the bed surface, leading to a reduction in the momentum transfer efficiency between the impacting particles and the bed particles. These results provide new insights into aeolian splash dynamics of steady‐state aeolian transport.