Shan and Chen Multiphase Oscillations with Bounceback Boundaries


Recently I have been attempting to model supercritical fluids using the Shan/Chen interparticle potential method. I have verified the model is working in the multiphase regime and in the single phase regime with period boundaries, however, when I operate in the single phase regime with bounceback boundaries, there are strange density and velocity oscillations that occur, and do not dampen out.

I have noticed that at iteration 0, where every node should be at equilibrium, there is a strange bound around the outside (one node inside of the bounce back boundaries). I think this is why the oscillations are occurring, however I am not sure how to fix it. I have attached an image of the velocity profile at iteration 0, at which the velocity on all nodes should be 0. The z-direction is periodic while the x and y have bounceback boundaries.

Any help or suggestions would be much appreciated.