[gooya_kabir]

Hello All,

I am working on the dynamic contact angle in two phase flow, interFoam. I want to print out the

uwall

during the solving, which is one of variables in the

PHP Code:

/src/transportModels/twoPhaseProperties/alphaContactAngle/dynamicAlphaContactAngle 


. I don't know where and how should I do this?

Thank you very much and looking forward to hear from you

[Nicole]

Hi Reza,

What is uwall? Is it a field like volVectorField, volScalarField, or a single value such as a scalar or dimensionedScalar?

Sorry, I am not familiar with this solver or what uwall is.

[gooya_kabir]

Hi Nicole,

It is a scalar field and it is sort of velocity of closest cell to the wall. but I don't know how to print it out.

Thanks

[Nicole]

Hi Reza,

I just used grep to search for uwall inside the solver code and it is not there. Where is this velocity calculated?

Can you not use paraview to visualise it?

[matejmuller]

Hi!

Have you tried the wallGradU utility? I think it gives the near wall U values. Otherwise, you can use the R utility and use this thread to calculate u+ (If you're looking for the u+ values, this is u+=U/U_tau) http://www.cfd-online.com/Forums/mai...ar-stress.html

Hope this helped, matej

[gooya_kabir]

Originally Posted by Nicole

Hi Reza,

I just used grep to search for uwall inside the solver code and it is not there. Where is this velocity calculated?

Can you not use paraview to visualise it?

Dear Nicole,

As it is here:

PHP Code:

/src/transportModels/twoPhaseProperties/alphaContactAngle/dynamicAlphaContactAngle 


the problem is how to print values which are in \src.

thanks

[gooya_kabir]

Originally Posted by matejmuller

Hi!

Have you tried the wallGradU utility? I think it gives the near wall U values. Otherwise, you can use the R utility and use this thread to calculate u+ (If you're looking for the u+ values, this is u+=U/U_tau) http://www.cfd-online.com/Forums/mai...ar-stress.html

Hope this helped, matej

Thank you matej,

I will try to see how can I get it with GradU, because it is not exactly the GradU close to the surface, actually it is: inner product of normal to wall and Uwall.

Thanks

[Nicole]

Hi Reza,

This is probably an awful hack.... but what I would try is to declare uwall in createFields and see if this brings it into the scope of the solver. If that fails you could try also copy that file you shared into your solver so that you include it from there directly which might make the variable available to you.

But this is definitely an awful hack way of doing it, hopefully someone who knows c++ better can tell me what an awful idea this is and give you some better help

[Mojtaba.a]

Well by taking a look at the code, uWall is used in member function which calculates theta:

Foam::tmp<Foam::scalarField>
Foam::dynamicAlphaContactAngleFvPatchScalarField::theta
(
    const fvPatchVectorField& Up,
    const fvsPatchVectorField& nHat
) const
{
    if (uTheta_ < SMALL)
    {
        return tmp<scalarField>(new scalarField(size(), theta0_));
    }

    const vectorField nf(patch().nf());

    // Calculated the component of the velocity parallel to the wall
    vectorField Uwall(Up.patchInternalField() - Up);
    Uwall -= (nf & Uwall)*nf;

    // Find the direction of the interface parallel to the wall
    vectorField nWall(nHat - (nf & nHat)*nf);

    // Normalise nWall
    nWall /= (mag(nWall) + SMALL);

    // Calculate Uwall resolved normal to the interface parallel to
    // the interface
    scalarField uwall(nWall & Uwall);

    return theta0_ + (thetaA_ - thetaR_)*tanh(uwall/uTheta_);
}

I think the best solution would be to make a new similar member function, but this time only to calculate uWall. Maybe something like:

Foam::tmp<Foam::scalarField>
Foam::dynamicAlphaContactAngleFvPatchScalarField::uWall
(
    const fvPatchVectorField& Up,
    const fvsPatchVectorField& nHat
) const
{
    const vectorField nf(patch().nf());

    // Calculated the component of the velocity parallel to the wall
    vectorField Uwall(Up.patchInternalField() - Up);
    Uwall -= (nf & Uwall)*nf;

    // Find the direction of the interface parallel to the wall
    vectorField nWall(nHat - (nf & nHat)*nf);

    // Normalise nWall
    nWall /= (mag(nWall) + SMALL);

    // Calculate Uwall resolved normal to the interface parallel to
    // the interface
    return nWall & Uwall;
}

Then you may write down the values to the disk, either by solver or a simple swak function object.

Best.