[Stefanie.S.W.]

Hello everyone,



i have some trouble to run a simulation with

3 phases (Water Oil Air)

2 Inlets (Water Oil)

and one outlet (plus large atmosphere)

using multiphaseEulerFoam.
I build a 2D box with 2 small inlets next to large atmospheres (top) and one outlet at the bottom of the box. Also I use a finer Mesh in inlet regions (see pictures "setup" and "Mesh").

I do not understand where the physics goes wrong with my boundary conditions (see screenshot at 1 sec). at a certain point my velocities change drastically and the time steps decline.


Maybe the mistake is related to the phi.xx-therms in U.xx. Or with the outlet BC. Or it is something completely different.

Hopefully you can help me to find the mistake and/ or fix the BCs. I am grateful for your suggestions and tips!



I have a Groovy BC for U.Oil which looks like this:

FoamFile
{
version 2.0;
format ascii;
class volVectorField;
location "0";
object U.oil;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
wall
{
type fixedValue;
value uniform (0 0 0);
}
atmosphere
{
type pressureInletOutletVelocity;
value $internalField;
}
outlet
{
type inletOutlet;
value $internalField;
inletValue uniform (0 0 0);
}
inlet_rain
{
type fixedValue;
value uniform (0 0 0);
}
inlet_oil
{
type groovyBC;
valueExpression "time()<179.99 ? vector( 0, -(((180-time())/180)*1), 0) : vector(0,0,0)";
value uniform (0 0 0);
}
}

Alpha.Oil respectively:

inlet_oil
{
type groovyBC;
valueExpression "time()<180 ? 1 : 0";
value uniform 0;
phi phi.oil;
}

p and p.rgh look like this:

FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [1 -1 -2 0 0 0 0];

internalField uniform 0;

boundaryField
{
wall
{
type zeroGradient;
}

inlet_rain
{
type fixedFluxPressure;
value uniform 0;
}

inlet_oil
{
type fixedFluxPressure;
value uniform 0;
}

outlet
{
type fixedValue;
value uniform 0;
}

atmosphere
{
type fixedValue;
value uniform 0;
}

defaultFaces
{
type empty;
}
}

I will attach the whole case.

You find "Constant" in the next comment.



This is an excerpt of the log file after the simulation "crashed"

Courant Number mean: 0.0471511 max: 0.990166
deltaT = 3.29388e-14
Time = 42.2803

MULES: Solving for alpha.water
water volume fraction, min, max = 0.000206908 -4.27083e-16 1
MULES: Solving for alpha.oil
oil volume fraction, min, max = 0.00279786 -2.04073e-18 1
MULES: Solving for alpha.air
air volume fraction, min, max = 0.996995 0 1
Phase-sum volume fraction, min, max = 1 1 1.06134
MULES: Solving for alpha.water
water volume fraction, min, max = 0.000206888 -4.27731e-16 1
MULES: Solving for alpha.oil
oil volume fraction, min, max = 0.00279779 -1.97791e-18 1
MULES: Solving for alpha.air
air volume fraction, min, max = 0.996995 0 1
Phase-sum volume fraction, min, max = 1 0.999998 1.06134
MULES: Solving for alpha.water
water volume fraction, min, max = 0.000206869 -4.28377e-16 1
MULES: Solving for alpha.oil
oil volume fraction, min, max = 0.00279773 -1.91774e-18 1
MULES: Solving for alpha.air
air volume fraction, min, max = 0.996995 0 1
Phase-sum volume fraction, min, max = 1 0.999996 1.06134

Thank you for your time and help!