Shock wave propagation in vibrofluidized granular materials

Shock wave formation and propagation in two-dimensional granular materials under vertical vibration are studied by digital high speed photography. The steepen density and temperature wave fronts form near the plate as granular layer collides with vibrating plate and propagate upward through the layer. The temperature front is always in the transition region between the upward and downward granular flows. The effects of driving parameters and particle number on the shock are also explored.Comment: 9 pages, 4 figures, submitted to PR

Formation and transportation of sand-heap in an inclined and vertically vibrated container

We report the experimental findings of formation and motion of heap in granular materials in an inclined and vertically vibrated container. We show experimentally how the transport velocity of heap up container is related to the driving acceleration as well as the driving frequency of exciter. An analogous experiment was performed with a heap-shaped Plexiglas block. We propose that cohesion force resulted from pressure gradient in ambient gas plays a crucial role in enhancing and maintaining a heap, and ratchet effect causes the movement of the heap. An equation which governs the transport velocity of the heap is presented.Comment: 9 pages, 5 figures, submitted to PR

Active thermal convection in vibrofluidized granular systems

We present a granular-hydrodynamic model that captures the essence of convection in a fully vibrofluidized granular system. The steady temperature distribution is solved analytically. Numerical simulation shows that the convection always develops through a supercritical bifurcation, with its energy about $5\%$ of the random (heat) one. A comparison calculation is performed for a normal fluid. The convection roll, or an active roll as we call it, has an angular velocity gradient from its interior to exterior. We conclude that active rolls are universal. Copyright Springer-Verlag Berlin/Heidelberg 2004