Frictional Fluids II

This movie shows what happens when you inject a gas into a granular suspension at different injection rates. At low rates, “stick slip” bubbles emerge, followed by “temporal intermittency” where periods of continuous motion are interrupted by occasional jamming. Increasing the injection rate further produces a spectacular “coral”-like pattern, and ultimately destabilized viscous fingers appear at high rates.

Labyrinth

A labyrinth pattern self assembles as a granular suspension dries out. The material is sandwiched between to glass plates, and fluid is withdrawn through a tube and a hole in the centre of the top plate. Fingers of air sweep up the granular material – glass beads of 100 micrometer average diameter – and produce a simply connected branching labyrinth. The constant spacing between the branches represents a balance between friction and surface tension at the interface. The initial disc is 35 cm across.