MUSIG convergence difficulties
I am performing a steady state simulation of air water bubbly flow in a vertical pipe. I have a converged solution with a monodispersed set up.
I am now trying to do a polydispersed MUSIG model. The residuals of the size group equations are just oscillating around RMS 1E-2. All other residuals are well converged. I am monitoring the volume fraction at the outlet. It is oscillating rapidly with a very small amplitude, however the mean value has been constant for quite a while and not moved far from the monodispersed result.
I started with the auto timestep, I have tried increasing and decreasing it. I have tried 1 and 2 velocity groups with a number of different bubble sizes
No matter what I have tried the size fraction residuals will not decrease.