[tidal]

hi, guys, I want to simulate a simple ocean flow within a box domain. I am using interFoam. The alpha.water was defined by setField, and the rest is air. Can I only set the velocity of water? If I set the U.inlet a value, means both air and water have same inlet velocoty. That causes the interface between air and water unsteady. Is it possible to set U.water and U.air separately? Thank you.

[crubio.abujas]

Originally Posted by tidal

hi, guys, I want to simulate a simple ocean flow within a box domain. I am using interFoam. The alpha.water was defined by setField, and the rest is air. Can I only set the velocity of water? If I set the U.inlet a value, means both air and water have same inlet velocoty. That causes the interface between air and water unsteady. Is it possible to set U.water and U.air separately? Thank you.

Short answer is no. interFoam solves uses a VOF approach to model the multiphase, which it means that it solve the momentum equation just once for whatever fluid is in the cell. In the VOF model it is expected that the cell just contains one fluid or the other, although if there is a mix of both it interpolate the properties using the volume fraction.

If you really want to model two separate momemtum equations for each of the phases you need to use an Eulerian approach (multiphaseEulerianFoam, for example). In this solver you have those U.water/U.air files to handle, but this approach may be a little overkill as it is computationally more expensive.

As you have already two well separated phases you may want to use some kind of special boundary condition that only impose a velocity in a specific region. You can add an additional patch on the bottom of the domain and implement the velocity there. Other option is to just code in a boundary condition that suits your requirements. For example you can quickly do some test using rather codedFixedValue of codedMixed boundary conditions.

    leftWall
    {
        type             codedFixedValue;
        value           uniform (0 0 0);
        name           leftWall;
        code            
        #{

            const fvPatch& boundaryPatch = patch();
            const vectorField& Cf = boundaryPatch.Cf();
            vectorField& field = *this;

            const scalar ymax     =   0.2;        // Max Height to apply cond
            const scalar addV     =   0.3;         // X-Velocity [m/s]

            forAll(Cf, faceI) 
            {
                field[faceI] = Cf[faceI].y() < ymax ?  vector(vx, 0, 0) : vector(0, 0, 0);
            }
        #};

Or you can set a condition only on the "wet" region of the boundary using a reference to the field alpha.water:

    leftWall
    {
        type             codedFixedValue;
        value           uniform (0 0 0);
        name           leftWall;
        code            
        #{
            label ownName = this->patch().boundaryMesh().findPatchID("leftWall");
            const fvPatch& boundaryPatch = patch();
            const vectorField& Cf = boundaryPatch.Cf();

            const volScalarField& alphaW = 
                db().lookupObject<volScalarField>("alpha.water");
            const scalarField aWPatch(alphaW.boundaryField()[ownName]);

            const scalar minVOF     =   0.2;        // Max Height to apply cond
            const scalar addV     =   0.3;         // X-Velocity [m/s]

            forAll(Cf, faceI) 
            {
                field[faceI] = aWPatch[faceI] > minVOF ? vector(vx, 0, 0) : vector(0, 0, 0);
            }
        #};

Hopes it help!

[tidal]

Thank you. I think this will help me to define the region. I will try it. If other questions came out, I will come back.

[Naira]

I am applying the same boundary condition on inlet but it gives me that error


Cannot find patchField entry for outlet

[crubio.abujas]

Originally Posted by Naira

I am applying the same boundary condition on inlet but it gives me that error


Cannot find patchField entry for outlet

I think the code I shared is missing a clousure bracket, that may be causing the error by not recognizing the patches defined after it.