Saltation of cohesive granular materials

The wind-driven saltation of sand and snow shapes dunes and ripples, generates dust emission, and erodes the surface of the Antarctic ice sheet. Here, we use a model based on the discrete element method to simulate grain-flow interactions and study the effect of particle cohesion on saltation dynamics. The data contains the model output of granular splash simulations and saltation simulations. Granular splash, the main particle entrainment process in saltation, occurs upon impact of saltating particles with the granular bed. We performed Monte Carlo simulations of granular splash for loose sand grains and for cohesive ice grains. The analysis indicate that different values of cohesion have significant effects not on the number of splashed grains, on the ejection velocity, and the rebound velocity. In our saltation simulations, we trigger particle movement with a single splash event at the inlet section section and let the system evolve until steady state. Our results show that saltation over cohesive surfaces is difficult to initiate but easy to sustain at low wind speed. The occurrence of transport thus depends on the history of the wind speed, a phenomenon known as hysteresis. We also show that saltation over cohesive surfaces presents higher mass fluxes but requires longer distances to saturate, which increases the size of the smallest stable surface ripples. Our model results have implications for large-scale aeolian processes on Earth and Titan, where sand grains are thought to be very cohesive.风驱动的沙粒与雪粒跃移塑造了沙丘与沙纹的形态，引发扬尘过程，并侵蚀南极冰盖表面。本研究采用基于离散元法(Discrete Element Method)的模型，模拟颗粒流相互作用，探究颗粒黏聚力对跃移动力学的影响。 本数据集包含颗粒溅射模拟与跃移模拟的模型输出结果。颗粒溅射是跃移过程中主要的颗粒起动机制，当跃移颗粒撞击颗粒床层时即会发生。我们针对松散沙粒与黏性冰粒分别开展了颗粒溅射的蒙特卡洛(Monte Carlo)模拟。分析结果表明，黏聚力的不同取值对溅射颗粒数量无显著影响，但会显著改变抛射速度与反弹速度。 在跃移模拟中，我们通过入口截面处的单次溅射事件触发颗粒运动，令系统演化至稳态。结果表明，黏性床面的跃移过程难以起动，但在低风速条件下易于维持。因此，颗粒输运的发生取决于风速的历史变化，该现象被称为滞后效应。研究同时发现，黏性床面的跃移过程具有更高的质量通量，但需要更长的距离达到饱和状态，这会增大最小稳定表面沙纹的尺寸。本模型的研究结果对地球与土卫六(Titan)上的大规模风成过程具有参考意义，上述天体的沙粒被认为具有较强的黏聚力。