This is a recent space-time plot of a sandpile sinusoidally driven in the vertical direction at approximately 10 Hz with an amplitude of 3.08 mm. The granular material is Ottawa (smooth) sand.
The dimensionless acceleration \Gamma= a \omega2 g-1 = 0.94 (G=a w2 g-1, if your browser understands the face tag...) In other words, I am driving the system just below the critical \Gamma.
The picture axes are as follows: horizontal position within the cell goes across the picture from left to right and the scale is 0-15 cm; time goes from top to bottom, each line representing another time step from t=0 min to 150 min (2 ½ hours)
The intensity at each space-time location is a measure of the height of the sandpile at that particular time, scaled to occupy the full color scale. Dark blues correspond to a valley and reds are the peak of the sandpile
In the above case, the total range of heights was very small, so it
should not be inferred that the sandpile formed a large heap. Also very
interesting, you can see the migration of small sand particles that rose
to the surface of the sand pile in the first ½ hour towards the
left.
 Duke Physics |
 CNCS |
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