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Weak, strong and detached oblique shocks in gravity-driven granular free-surface flows

Gray, J. M. N. T. & Cui, X.

Journal of Fluid Mechanics, vol. 579 (2007),   pp. 113-136

If a movie is not displayed, please use the links in the caption to download it to your computer.

Movie 1. A video sequence showing the development of a weak shock in a laboratory experiment. The camera is positioned normal to a chute inclined at 38 degrees to the horizontal. Non-pareille sugar grains are stored in a hopper that is located upstream of the left-hand boundary. The avalanche is released by raising the hopper gate and flows downslope from left to right, quickly establishing a steady non-uniform flow. A wedge inclined at an angle of 20 degrees deflects the flow and a weak shock is formed at an angle of approximately 29 degrees. The Froude number just before the wedge is equal to 5. Note that the flow after the oblique shock lies parallel to the wedge. Download movie.

Movie 2. A video sequence showing the development of a strong shock in a laboratory experiment. The parameters are exactly the same as before, but now a second gate is placed downstream of the right-hand boundary. Initially this gate is closed and the chute is empty. Once the avalanche is released a weak shock forms along the wedge and an upslope propagating time-dependent strong shock is formed by the second blocking gate. Just before the shock reaches the wedge tip, the second gate is partially opened, and a steady strong shock forms provided the inflow and outflow mass fluxes balance. Download movie.

Movie 3. The formation of a detached oblique shock in a laboratory experiment. To acheive this, the downstream gate is discarded, the inflow Froude number is reduced to 4 and the wedge angle is increased to 44 degrees. A steady state is rapidly established with the flow detaching upstream of the wedge. Download movie.