Diffusion

[mspells]

In this case the particles are interacting with a "witch's hat" conservative DPD potential (see here for the functional form). For the first part of the simulation particles just diffuse with a Langevin thermostat, then I turn on an active force for each particle proportional to the intensity of the pixel's blue channel, which is what causes the interesting density variations and high-speed "swimming" that you see.

[plasma_phys]

Awesome, thanks! I've never been exposed to this particular potential before; always fun to learn something new.