风沙流中基于宏观颗粒模型的沙粒浓度分布

风沙侵蚀是造成土地沙化和干旱区地貌的主要原因,其中沙粒的浓度分布是研究输沙量、颗粒碰撞、风沙流结构等特征的主要影响因素,也是了解颗粒碰撞过程和风沙两相流耦合过程的重要研究内容。为了考虑沙粒与气流的力平衡、阻力和扭矩的变化、碰撞及摩擦等影响,运用了一种新的宏观颗粒模型(macroscopic particle model, MPM)研究沙粒在气流中的运动。与前人研究结果进行比较后发现,宏观颗粒模型在不需要任何附加模型的前提下,能实现风沙两相耦合的准直接数值模拟,根据沙粒运动速度云图所示的风沙流运动状态的不同,沙粒浓度的垂向分布会出现结论不一致的现象。颗粒流系统的内在非线性是造成风沙流运动状态不均匀、不一致的主要因素。数值模拟结果表明,利用MPM模型中的离散颗粒追踪、颗粒速度和位置等信息能够研究多相流条件下的风沙运动机理。

Study on the concentration distribution of sand particles in aeolian sand flow based on MPM

Aeolian sand erosion is the main cause of land desertification and arid landform.The concentration distribution of sand particles related to it is the main influencing factor to study the characteristics of sediment transport, particle collision and aeolian sand flow structure, as well as the most important research content to understand the process of particle collision and the coupling process of aeolian sand two-phase flow.In order to consider the influence of force balance resistance, torque, collision and friction, a new Macroscopic particle model(MPM) is used to study the movement of sand particles in the airflow.Compared with previous research results, it is found that the macro-particle model can realize the quasi-direct numerical simulation of two-phase coupling of aeolian sand without any additional model. According to the different movement states of aeolian sand flow shown in the cloud map of sand velocity, the conclusions of the vertical distribution of sand concentration are inconsistent.The inherent non-linearity of particle flow system is the main factor that causes the non-uniformity and inconsistency of aeolian sand flow state. The numerical simulation results show that the tracking function of discrete particles in MPM model and the information of particle velocity and position can be used to study the multiphase flow mechanism of aeolian sand movement.