Visualization of shocks in granular media

Granular flows exhibit interesting behavior as a result of complex interaction between the granular particles. This work visualizes the shock front resulting from granular flow over three cylindrical bodies having different cross-sectional shapes: circular, triangular and square, at three different flow velocities. The visualizations were done using the shadowgraph technique. The visualization data show well-defined shocks as well as some interesting instabilities in the granular media behind the shock fronts. The wave geometry resulted in estimation of the flow Mach number, the velocities of the granular particles and the speed of sound in the medium. The estimated flow Mach numbers were 6.9, 7.5 and 8.4. The estimation of the shock stand-off distance and radius of curvature of bow shock at the front stagnation point is also done for the cylindrical and square geometries. The oblique shock angle and the wake angle for the triangular model are also presented. Similarities of the wave features with continuum gas flows are discussed.