What outlet would I use with a mass-flow inlet in a mixed convection problem where I use the incompressible ideal gas law? The fluent manual says outflow can't be used with varying density.

thanks

Try using pressure outlet. In most cases it's value is known or can be measured easily.

What exactly does a pressure outlet in this situation impose on the model? By changing pressures at this outlet it can't 'pull' more mass or slow the inflow into the domain, since the mass inlet is fixed and it is incompressible?? Or does it just affect the pressure in the domain, but does this affect the outlet flowrate? can it affect the mass flowrate out of the domain? thanks

when and why we must assume that the second normal derivative of pressure is zero at outlet