摘要：
风沙运动是气流驱动地表沙粒向前输运的一种气-固两相流运动，是导致土壤侵蚀和沙漠化的直接原因。本研究基于离散元法模拟再现了沙粒在流体剪切力作用下从流体起动、跃移击溅直至稳态跃移的完整过程。对于流体起动过程，厘清了沙粒的流体起动机理和关键影响因素，构建了较为完整的沙粒流体起动方案；对于沙粒的跃移冲击过程，着重考虑了跃移沙粒的群体效应，发现其平均击溅效率比单粒子冲击高25% - 30%，基于此给出了基于冲击动量密度的群体粒子击溅模型；对于稳态跃移过程，发现每颗沙粒跃移循环通常包含数次至数十次单独的跳跃过程，并且其运动状态会在蠕移、蠕跃和跃移之间转变，揭示了实际风沙运动中反弹恢复系数对于入射速度具有极强的依赖性。本研究为更加深入认识自然风沙过程的相关运动特征奠定了基础，进而提高风沙输运过程的预测和模拟精度。
Abstraction：
Wind-blown sand movement is a gas-solid two-phase flow process that airflow drive surface sand particles to transport downstream, which causes soil erosion and desertification directly. In this study, we investigated the complete process from shear-borne aerodynamic entrainment of sand particles, to splash, and then to steady-state saltation. For aerodynamic entrainment, we clarified the aerodynamic entrainment mechanism and key influencing of this process, and further constructed a complete scheme for aerodynamic entrainment. Regarding the impact process of saltation sand particles, we discovered that the average splash efficiency of multi-particles is 25% to 30% higher than that of single-particle, with emphasis on the collective effect of saltation particles, and established a multi-particles splash model based on impact momentum density. For the steady state saltation process, we found that each sand usually undergoes several to tens of individual hop processes in each particle saltation cycle, and transitions between the motion states of creep, reptation and saltation due to the strong dependence of the rebound coefficient of restitution on the impact velocity in real wind-blown sand movements. This study provides a foundation for the deeper understanding of the relevant motion characteristics of natural wind-blow sand process, and further improves the prediction accuracy of aeolian transportation process.

风沙运动，流体起动，群体粒子冲击，稳态跃移，离散元法