MULTIPHASE - FREE SURFACE & MIXTURE MODEL

Aris

I try to model the flow into stratified sea. The cause for the stratification is the difference of the salinity. As I know, in Fluent I can't use the salinity as a parameter and calculate the density as a function of the salinity (and secondary of the temperature). So, I have thought to use the multiphase mixture model with two phases of liquid, (for example one with density 1010 and one with density 1025 kg/m3) and choose as initial condition the fraction of the two phases as a function of the depth.

On the other hand, the model requires free surface, so I need to use air as an additional phase including the VOF model. The conflict is that I can't use the VOF model and the mixture model simultaneously.

Any idea?