Role of shape on the forces on an intruder moving through a dense granular medium

Abstract: We use numerical simulation to investigate the effect an intruder's shape has on the drag and lift forces that it experiences while moving through a granular medium composed of polydisperse disks of mean diameter d. The intruder velocity,v, was varied from 0.1 \sqrt(dg) to 20 \sqrt(dg). For frictionless particles (\mu= 0.0)there is a gradual increase in drag force with increasing v, whereas for frictional systems (\mu= 0.1,0.5) a constant drag regime appears at low velocities. The drag force depends weakly on the shape of the object provided that the cross-section is same. The drag force depends linearly on the immersion depth, while there is very little variation in lift force with depth for certain shapes. The lift experienced by the object is a strong function of its shape at a given velocity. Shape has an effect on the distribution of contacts around the surface of the intruder which may result in a strong lift for certain shapes. We also show the force profiles around the intruder surface.