Eliminating spurious velocities in the free-energy lattice Boltzmann method.

Spurious velocities are unphysical currents that appear close to curved interfaces in diffuse interface methods. We analyze the causes of these spurious velocities in the free-energy lattice Boltzmann algorithm. By making a suitable choice of the equilibrium distribution, and by finding the best way to numerically calculate derivatives, we show that these velocities may be decreased by an order of magnitude compared to previous models. Furthermore, we propose a momentum conserving forcing method that reduces spurious velocities by another factor of approximately 5. In three dimensions we find that 19 velocity vectors is the minimum number necessary.