Horizontal size segregation in a vibrating granular layer
This is a dynamical simulation of a vertically vibrated layer of granular
material (the system is two-dimensional) driven by a base with a sawtooth
profile. Grains can escape over the barriers at either end of the base and also
through the opening on the right side. The underlying model consists of
disklike particles whose collisions are inelastic (the computational techniques
are the same as in molecular dynamics). The simulation region is vertically
periodic, and grains leaving through the bottom are reinjected at the top with
an inward-directed velocity.
After a sufficiently large number of cycles (typically 300) segregation will
start to become apparent, with the larger (red) grains moving towards the left.
This demonstrates that (at least in the simulations) vertical vibration is able
to produce horizontal size segregation, a totally unexpected phenomenon whose
existence has yet to be investigated experimentally.
The controls available to the user are the start/stop and restart buttons, and
a slider used to set the number of timesteps between display updates (a larger
value produces a faster but less smooth animation).
(c) D. Rapaport