Shown here is a 2-minute time-lapse photograph of ``booming dune sand'' -- scooped from the Mojave Desert with mean diameter, d=0.22 mm-- showing multiple co-rotating rolls. Near the surface on both sides of the photo, one can see the tracks of the sand avalanching down the hill and moving back to the top of the hill just under the surface boundary layer.
Occupying the majority of the photo, however, one can see a complicated
convection pattern where the sand is generally moving right to left across
the image, then getting ``caught'' in the stream moving to the surface of
the heap near the left edge of the cell.
 Duke Physics |
 CNCS |
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