Joule (Free) Expansion Based on a Block Cellular Automaton

container side length

60

120

240

480

computational gap size

1

6

8

12

24

trigger | pause equilibration

abort and initialize, uncheck to restart

In this Demonstration a rigid square container is divided into two compartments of equal volume separated by a rigid dividing barrier with an adjustable gap in the middle. The container is thermally isolated from its surroundings. At startup, the left compartment contains an ideal gas exerting a pressure

P

i

and the right compartment is evacuated. The gas expands to fill the entire two-compartment volume by way of collision-driven particle transfer between the two compartments. Moreover, the expansion proceeds ultimately to equalize the pressure on the two sides of the dividing barrier. Turbulence is evident at many places in both compartments as the expansion proceeds.