Pressure dissipation problem in bubble simulation (Riemann problem)
 

Hi,

I am simulating a low pressure air bubble inside a high pressure liquid. Basically this is a Riemann problem. The problem is when I assume the liquid to be incompressible, as soon as the simulation starts, the pressure will be diffused between the high and low pressure regions (it will look like a rainbow of colors).

However, if I set the liquid to be compressible, the pressure diffusion will not happen as bad as before but it is still significant. I have attached a figure to better show this.

My question is which solver settings, discretization method, etc should I use to prevent this artificial pressure diffusion. I should say reducing grid and time step has not helped at all.


P.S. I should mention that when I do the same settings as above to model a shock tube (low pressure air and high pressure water), the pressure diffusion does not happen and everything works fine.

Any ideas?

The attached figure is when liquid is set to be compressible.
Attachment 39909