Issue when assigning mass-flow outlet for Multiphase flow

allenpvallenpv Member Posts: 4

I am studying the effect of change in gravity on a tank that is filled up to a certain volume with liquid N2. When I initialize the problem and patch a specific region to be only N2 liquid, at the location of the outlet, a layer of N2 gas is formed. Not sure why this is the case, but it only happens when I assign the boundary as massflow_outlet.

So as part of the mass flow rate settings, I assigned a 0kg/s mass flow rate for N2gas and 0.5 kg/s for N2 liquid. But since there was this layer of N2 gas just below the outflow tube, it caused a floating point error.

How I fixed it, is I assigned the outlet as simple pressure_outlet and ran it for 10 iterations, then I switched the outlet back to Mass_flow outlet. In those 10 iterations, the layer of gas goes away and then using mass_flow outlet causes no problems.

Am I doing something wrong? Is this expected behavior?


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