[baran_foam]

Greeting all,

I have some silly doubt....regarding postprocessing utility wallHeatFlux...it was unable to read my bc at wall of const heat flux in fluid region and it read it as zero....

https://www.dropbox.com/s/1k095xfi7e...subir.zip?dl=0

I am using this command...
wallHeatFlux -region cavityAir
wallHeatFlux -region cavityAir -time 4000

Can anyone kindly specify me that what is the problem here...about constant heat flux at wall bc..?

regards,
baran

[wyldckat]

Hi Baran,

Thanks for posting this question here in the public forum, since this question can help others in the future.

I took a somewhat quick look at this case and there is something strange I saw: the wall patches "w_he_*" in the region "cavityAir" are defined as boxes. In other words, each one of these patches is defined with 6 sides, making it a closed surface. in theory, this shouldn't be much of a problem, but it could lead to one of those situations where it cancels each other out.

Now, I took a better look at the boundary conditions and in the file "0/cavityAir/T" is this:

    w_he_4
    {
        type            compressible::turbulentHeatFluxTemperature;
        heatSource      power;
        q               uniform 110.4;
        K               basicThermo;
        KName           none;
        Qr              none;
        value           uniform 300;
    }

while in "alphat" on the same folder:

    w_he_4
    {
        type            alphatWallFunction;
        Prt             0.85;
        value           uniform 0;
    }

If we look at the iteration/time 4000, the "alphat" field didn't change for these walls. And the equation calculated in wallHeatFlux is this:

        surfaceScalarField heatFlux
        (
            fvc::interpolate(RASModel->alphaEff())*fvc::snGrad(h)
        );

But since "alphat" is still zero at the iteration/time 4000, then the result is also zero.

Of course now the question is: why is "alphat" zero on these walls?

Honestly, I don't know. My guess is that it might have something to do with the fact that you grouped the 6 surfaces into 1 on all of the 4 groups of walls "w_he_*".


My advice is what I usually tell people: first test with a simpler case. For example: http://openfoamwiki.net/index.php/Ge..._-_planeWall2D
Otherwise, there are too many possibilities for things that could go wrong.

Best regards,
Bruno

[baran_foam]

Greeting all,
@bruno ,Thanks for your suggestion... i am trying to use the utility of wallHeatFlux for single wall ...but still it is showing zero value for constant heat flux boundary condition.....

Regards,
baran

[wyldckat]

Hi Baran,

I simply don't know why this is happening. A few questions:

1. What does the "alphat" field have for each one of those single walls for the iteration 4000?
2. Did you try to create a simpler case that can more easily be diagnosed?

Best regards,
Bruno

[baran_foam]

Hello Bruno,
I check tutorial case having simple geometry. It shows the heatFlux boundary condtion as zero value with one face only.
Another thing is that it is for laminar case...so may be alphat is not there...
So I am trying to check this case with turbulece model....
here alphat is in order of 10^-5 value ...heat flux is giving zero value...

Regards,
baran

[dewey]

Hi

could you find how to put heatflux as Bc?