标题： 沙丘-沙丘斥力的颗粒尺度研究 显示英文标题

标题： Barchan-barchan dune repulsion investigated at the grain scale

摘要： 沙丘是地球上、火星和其他天体上发现的新月形风成沙丘。 在不同类型的沙丘-沙丘相互作用中，有一种被称为追逐的现象，其中沙丘保持接近但不相互接触。 在本文中，我们通过进行颗粒尺度的数值计算来研究这种沙丘-沙丘排斥的起源，在计算中，颗粒堆被流体流动变形为相互作用的沙丘。 在我们的模拟中，每个时间步长都会计算每个颗粒的位置、速度和合力，使我们能够测量流体和颗粒的细节，以解释排斥现象。 我们展示了颗粒的轨迹、时间平均合力以及每个沙丘的质量平衡，并表明下游沙丘比上游沙丘收缩得更快，从而保持相对较高的速度，尽管位于上游沙丘的尾流中。 反过来，这种快速收缩是由于流体扰动引起的，这导致下游沙丘受到更高的侵蚀，并且颗粒从上游沙丘离开后绕过下游沙丘。 我们的结果有助于解释地球上和火星上沙丘场中沙丘分布背后的机制。 显示英文摘要

摘要： Barchans are eolian dunes of crescent shape found on Earth, Mars and other celestial bodies. Among the different types of barchan-barchan interaction, there is one, known as chasing, in which the dunes remain close but without touching each other. In this paper, we investigate the origins of this barchan-barchan dune repulsion by carrying out grain-scale numerical computations in which a pair of granular heaps is deformed by the fluid flow into barchan dunes that interact with each other. In our simulations, data such as position, velocity and resultant force are computed for each individual particle at each time step, allowing us to measure details of both the fluid and grains that explain the repulsion. We show the trajectories of grains, time-average resultant forces, and mass balances for each dune, and that the downstream barchan shrinks faster than the upstream one, keeping, thus, a relatively high velocity although in the wake of the upstream barchan. In its turn, this fast shrinkage is caused by the flow disturbance, which induces higher erosion on the downstream barchan and its circumvention by grains leaving the upstream dune. Our results help explaining the mechanisms behind the distribution of barchans in dune fields found on Earth and Mars.