unsteady solver and density method

Ellen

Hi,

I'm trying to model a flow with species transport. When specifying the density of the gases, I tried two methods: using ideal-gas law or using measured density values at discrete points (by reading in a density table). Both methods worked fine with steady state simulation, however, when I changed to unsteady solver, the case with ideal-gas method still ran ok, but the case with density table had the divergence problem (Error: divergence detected in AMG solver!). All the other settings are kept the same for the two cases, so I can't figure out why the density method makes such a big difference in unsteady simulations.

Does anyone here has the answer for this? Thank you very much.

Ellen