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Breaking size segregation waves and particle recirculation in granular avalanches

Thornton, A. R. & Gray, J. M. N. T.

Journal of Fluid Mechanics, vol. 596 (2008),   pp. 261-284

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Movie 1. Wave Breaking problem. Animation showing the evolution of a breaking size segregation wave in a frame (ξ,z) moving downstream at the same speed as the steady-state lens ulens = 1. A series of stills for this problem are illustrated in figure 6 and the final steady state is shown in figure 4(a). The initial condition consists of a linearly decreasing concentration shock that joins two constant height sections. In response to linear shear through the avalanche depth the shock steepens and breaks at t = 1 to form an oscillating lens. Computations are performed on a 300 x 300 grid and with Sr = 1. Contours of the small particle concentration are illustrated using the colour bar below, with red corresponding to pure fines and blue to pure large. For t > 20 the time-step is increased to speed up the convergence towards the steady-state solution. Download movie.

Colourbar used in animations

Movie 2. Lens interaction. Animation showing the development of the small particle concentration during the interaction of two breaking size segregation waves in a frame (ξ,z) moving downslope with speed unity. A series of stills for this problem are illustrated in figure 8 and the final steady state is shown in figure 4(a). At t = 0 the sharp downward steps in concentration break to form two lenses that propagate in opposite directions with speed 0.4. Just after t = 3 these begin to coalesce to form a single lens between Hup = 0.9 and Hdown = 0.1 that propagates downslope with speed unity. The results are for linear shear and Sr = 1. Computations are performed on a 300 x 300 grid and contours of the small particle concentration are illustrated using the colour bar above, with red corresponding to pure fines and blue to pure large. For t > 20 the time-step is increased to speed up the convergence towards the steady-state solution. Download movie.