DEFINE_MASS_TRANSFER convergence

Robert

Dear all, I would like to simulate a flow, where water goes to vapor. The water goes to vapor, when the pressure reaches the critical pressure, and the vapor overexpanding. I wrote an UDF, which calculate the phase change (DEFINE_MASS_TRANSFER). I use the mixture multiphase model with SST k-omega model.

The problem: I can not reach convergence. I tried to decrease the under relaxation factors (for example: Momentum=0.01), but it is still very unstable and doesn't converge. Can somebody help me, how can I reach convergence, when I use MASS_TRANSFER macro to simulate the phase change? It is very urgent.

Thanks a lot!

Robert