Pictures from the Growth of Granular Piles

The colour code is:

Time runs from left to right
Pile (above) grown from low density feed. The front is very sparse, and this case is quite close to sequential placing of particles.
Pile (above) grown from higher density feed. The front now has significant thickness.
Pile (above) grown from our highest density feed. By this stage the front tends to dominates over the depth of the pile.