5. Granular dynamics
Chute flowBy extending the molecular
dynamics approach to include frictional forces it becomes possible to model the
flow of granular materials. This is an example (in two dimensions) of flow down
an inclined chute; the larger grains are seen to rise gradually to the top of
the bulk. Here is a
short animation sequence (350K).
Funnel flowFlow of granular material through
an opening is widely encountered in industrial processing and storage. Here is
a short animation sequence showing stresses experienced by the grains (1200K).
Vibrated layerSurface waves appear when a
granular layer is vibrated vertically. Here, the container has periodic sides
and the base oscillates. The type of wave depends on the details; the
self-organized behavior is fascinating to watch. Here is
an animation sequence showing the wave behavior (880K).
Axial segregation in a rotating
cylinderAxial segregation occurs in rotating horizontal cylinders that are
partially filled with mixtures of two different kinds of granular particles. The
behavior depends on the particle properties (relative size, roughness). Shown
below is a small (three-dimensional) system displaying this behavior. Here is
an animation sequence showing segregation in a smaller system (1000K).
Radial segregationRadial segregation is
another phenomenon associated with rotating cylinders. An example of what occurs
(in two dimensions) appears below. Here is
an animation sequence showing how the segregation develops (rotation is in the
counterclockwise direction) (1050K).