Spinodal decomposition (Lattice-Boltzmann)

A two dimensional two-phase fluid was modelled on a lattice. The Boltzmann equation was solved, using the LB2D code, written by Jonathan Chin, at that time in Peter Coveney's group. This was part of the mesoscale workshop at the 2002 CCP5 Summer School on Molecular Simulations, King's College, London.

Using the Boltzmann equation to describe transport processes includes both diffusion (random walk of particles) and hydrodynamics (collective transfer of mass and momentum). One interaction parameter determines how strongly the two phases "dislike eacho other".

In the animations below (click on the still image to see the animations), the demixing (spinodal decomposition) of two immiscible but initially finely dispersed phases is simulated (think of oil and vinegar separating in a vinaigrette). With increasing interaction parameter the fluids demix much faster.

Initially, the demixing is diffusive but becomes soon hydrodynamic in nature when larger volumes of one phase move and coalesce---bubbles and droplets move instead of single fluid particles. The 1.5-nh simulation switches off the hydrodynamic interactions and shows how little demixing occurs if only diffusion takes place.

spinodal-1.4.gif 10724125 bytes 256 x 256

spinodal-1.5-nh.gif 2017347 bytes 128 x 128 no hydrodynamics

spinodal-1.5.gif 2017347 bytes 128 x 128

spinodal-1.8.gif 681099 bytes 128 x 128

SBCB   |  O.B.  |  Research  |  Publications  |  Non-work