[Gearb0x]

I am working on a single inlet/outlet geometry using the twoLiquidMixingFoam solver (for simulating gas but as a first step, I assume compressible effects are negligible).
A stratification exists within the geometry and then some inflow comes and disturbs the stratification.
I am encountering some issues with the case so I would like to "simplify" it to rule out the potential culprits.

First thing I would like to do is to delete the outlet. So my geometry would simply consist of the mixture inside the geometry and then an incoming flow from the inlet.

The boundary conditions are therefore set the following way with the intent to make the "outlet" patch behave like a wall (since for now I want to remove the outlet) :


U file

boundaryField
{
    frontAndBack
    {
        type            empty;
    }
    walls
    {
        type            noSlip;
    }
    inlet
    {
        type            flowRateInletVelocity;
        massFlowRate    constant 0.01
	rhoInlet        1.184; // 1.184 density of air
    }
    outlet
    {
        type            noSlip; 
    }
}

p_rgh file

boundaryField
{
    frontAndBack
    {
        type            empty;
    }
    outlet
    {
	type            zeroGradient;
    }
    inlet
    {
        type            zeroGradient;
    }
    walls
    {
        type            zeroGradient;
    }
}

alpha.x

boundaryField
{
    frontAndBack
    {
        type            empty;
    }
    walls
    {
        type            zeroGradient;
    }
    inlet
    {
        type            fixedValue;
        value           uniform 0;

    }
    outlet
    {
        type            zeroGradient;
    }

}

but then I get the following error :

Continuity error cannot be removed by adjusting the outflow.
Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow.
Total flux              : 0.000645087
Specified mass inflow   : 0.0128378
Specified mass outflow  : 0
Adjustable mass outflow : 0

So somehow the solver (twoLiquidMixingFoam) does not like having only one inlet and no outlet ?

[louisgag]

Hi Gearb0x,

I am not familiar with your solver and with multiphase flow but I think you cannot have boundary conditions as such. If you have an inlet you must have an outlet, otherwise you are trying to compress the fluid... Perhaps you could get away with using an outletInlet boundary, but I haven't tried. See this for more info: https://www.openfoam.com/documentati...conditions.php


-Louis

[Gearb0x]

Yes indeed pressure would increase in my case. But I did not think this would be an issue.

[louisgag]

I think more than the pressure the issue comes from the mass coming in... You have flow in, so mass, and nothing coming out, so density must increase, but the flow is incompressible.. Correct me if I'm wrong!

[Gearb0x]

Indeed, that must be the issue!

[jaydeep]

You could try mixed boundary that adjusts inflow based on pressure?

something of the nature pressureInletOutletVelocity?

[Bodo1993]

Hi,
I am using twoLiquidMixingFoam with one inlet and two outlets. I get some vortices at the outlet when the mixed phase reaches there.
Here is a description of my problem
I would appreciate your assistance.
Thanks.