Compartmentalized granular gases
Devaraj van der Meer has been studying granular matter and fluid physics for over a decade and in the process, he’s exposing their beauty for all to see. You can find a ton of aesthetically pleasing clips on his website; http://stilton.tnw.utwente.nl/people/devaraj/research.html
Excited granular matter is a rich pattern-forming system. The un-mixing or segregation of unlike grains under vibration and flow is a good example and one you might know from the so-called Brazil nut effect where Brazil nuts rise to the top of a packet of mixed nuts when shaken.The cause of this effect is that when shaken, granular (and some other) materials move in a circular pattern. some larger materials (Brazil nuts) get stuck while going down the circle and therefore stay on the top.
Clip below; What started out as a high-school demonstration of the equipartition of gases turned into a prime example of symmetry breaking: When a container, separated int two by a wall, is filled with glass beads and shaken mildly, the beads spontaneously cluster into one of the two compartments. This can be explained from the inelastic collisions between the particles: If one of the compartments, by chance, contains more particles, more energy is lost, particles become slower and jump less easily over the wall. Due to this snowball effect the dense compartment becomes even denser and the dilute one more dilute, until a dynamical equilibrium sets in.
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