稀颗粒流中非对称障碍物上的升力
Lift force on an asymmetrical obstacle immersed in a dilute granular flow
摘要：
本文通过解析计算和计算机模拟研究了颗粒流中椭圆形障碍物所受的升力。结果示出为障碍物的大小，相对于流动方向（倾斜角）的取向，恢复系数和椭圆偏心率的函数。理论上的论点，根据施加在障碍物上的力，由于非弹性，无摩擦碰撞的一个非常稀的流，捕捉定性特征的升降机，但未能再现的数据定量。这一分歧背后的原因是，作为这一论点基础的稀流假设在障碍物前形成颗粒激波时被打破了。更具体地说，冲击波改变了颗粒在障碍物处的冲击速度，降低了从非常稀的流获得的总净升力。
英文摘要：
This paper investigates the lift force exerted on an elliptical obstacle immersed in a granular flow through analytical calculations and computer simulations. The results are shown as a function of the obstacle size, orientation with respect to the flow direction (tilt angle), the restitution coefficient and ellipse eccentricity. The theoretical argument, based on the force exerted on the obstacle due to inelastic, frictionless collisions of a very dilute flow, captures the qualitative features of the lift, but fails to reproduce the data quantitatively. The reason behind this disagreement is that the dilute flow assumption on which this argument is built breaks down as a granular shock wave forms in front of the obstacle. More specifically, the shock wave change the grains impact velocity at the obstacle, decreasing the overall net lift obtained from a very dilute flow.
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