(a) Frontal view of the chute, sandpaper is glued on the chute; (b) the laboratory chute in action: the hatch has been opened manually and the ballotini flow down the chute. Strobes illuminate for the high-speed cameras; (c) image of the flow of a medium ballotini avalanche recorded by the high-speed camera; computed velocity field (arrows) and horizontally averaged grey level of the image (mid-grey—red curve) are superimposed.
The evolution of the velocity profile for three medium ballotini avalanches at a 35° inclination on the three different running surfaces. (a) smooth running surface, (b) rough running surface, (c) very rough running surface. t1 to t7 refer to different times in the high-speed movie. Profiles are plotted every 0.25 s on the smooth running surface and 0.33 s on the rough and the very rough running surface.
The evolution of the velocity profile for a small ballotini (a) and a large ballotini (b) avalanche at a 35° inclination on the rough running surfaces. t1 to t7 refer to different times in the high-speed movie. Profiles are plotted every 0.33 s.
Evolution of the velocity profiles for two medium ballotini avalanches at two different inclination angles: (a) 30° and (b) 40° .
Evolution of the flow depth (a) and the depth averaged velocity (b) in the medium ballotini avalanches when flowing on different running surfaces.
Depth averaged downstream velocity v m , slip velocity v s and surface velocity v t for two medium ballotini avalanches with the same experimental parameters: 30° inclination, rough running surface.
Definition of the framework: observation of the avalanches through a side-wall of the chute reduces the problem to two dimensions.
Velocity profile shape factors of three medium ballotini avalanches flowing on different running surfaces at 35° inclination.
Material properties of the ballotini.
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