Node160 - CFD SUPPORT

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Multiple Reference Frame - MRF

We start by copying of the mesh we have just created to MRF directory.
# cp -r wholeMesh/constant/polyMesh MRFCase/constant
We need to setup initial conditions for water. So we copy file alpha.water.org to working copy.
# cd $FOAM_RUN /mixerCase/MRFCase
# cp 0/alpha.water.org 0/alpha.water

To fill mixer tank by water we will use utility setFields what is configured by file setFieldsDict.

defaultFieldValues
(
        volScalarFieldValue alpha.water 0
);

regions
(
        boxToCell
        {
                box ( -0.20 -0.15 -1 ) ( 0.2 0 1 );
                fieldValues
                (
                        volScalarFieldValue alpha.water 1
                );
        }
);

We run it
# setFields
The last thing to be set up is the mixer rotation.
In this section we will use the Multiple Reference Frame method, which is used for the stationary flow solution computation.
To simulate the rotation, the real movement of the mesh is substituted by momentum sources in the stationary cells – we add the so called Coriolis term.
We need to choose the rotating zone, where we simulate the rotation. To do this, we need the topoSet utility and create a cellZone.
We choose the cells with the center of gravity inside of the cylinder with base radius m, which is the maximum distance, where the mixer blades would rotate if they were actually rotating

Let us look at topoSetDict.
# cat system/topoSetDict

actions
(
        {
                name    rotor;
                type    cellSet;
                action  new;
                source  cylinderToCell;
                sourceInfo
                {
                        p1 (0 0 0);
                        p2 (0 0 0.1);
                        radius 0.04123;
                }
        }
);

We create a cellSet called rotor and convert the cellSet to a cellZone
# topoSet
# setsToZones

Let us look at MRFProperties
# cat constant/MRFProperties

MRF1
{
    active          true;
    cellZone        rotor;

    origin      (0 0 0);
    axis        (0 0 1);
    omega       6.28318;
}

and transport properties in file transportProperties.
# cat constant/transportProperties

phases ( water air );

water
{
        transportModel  Newtonian;
        nu              nu [ 0 2 -1 0 0 0 0 ] 1e-06;
        rho             rho [ 1 -3 0 0 0 0 0 ] 1000;
}

air
{
        transportModel  Newtonian;
        nu              nu [ 0 2 -1 0 0 0 0 ] 1.48e-05;
        rho             rho [ 1 -3 0 0 0 0 0 ] 1;
}

sigma                   sigma [ 1 0 -2 0 0 0 0 ] 0;

At last we run the solver:
# interFoam > log.interFoam &

Figure: MRF method results visualization

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