Granular Flow Dynamics on an Inclined Plane

Avalanche Dynamics

Avalanches under constant flux conditions on an inclined plane have very different dynamics depending upon the form of the grains. Here we show two realizations of avalanches - one for spherical glass beads and the second for rough non-spherical sand.

Sand Avalanche Field

Two sand avalanches are visible. These are difference images so that large differences at the front of the avalanche are dark.Viewed from the top glass and sand avalanches are similar although sand avalanches have side tails whereas the glass avalanches are more oval in shape.

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Avalanche Height

In addition to the lateral extent of the avalanche, we use a laser line projected either along the flow or perpendicular to the flow. A picture and movie of the laser line as an avalanche passes by are show:

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When projected across the layer, one can reconstruct the height profile of the avalanche (assuming that it does not change much during the time it passes the laser line).

A reconstructed height profile for a glass bead avalanche:

The very different nature of the avalanches can be seen from the side.

Glass Avalanche viewed from the side

Notice how the bed in front of the avalanche seems to collapse, i.e., start moving before the bulk of the avalanche arrives.

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Sand Avalanche viewed from the side.

Notice how the grains of the avalanche move over a quiescent solid bed and move faster than the avalanche front.

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