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Impose a flux at BC for the transport of a scalar

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Old   March 28, 2012, 10:08
Default Impose a flux at BC for the transport of a scalar
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Cyp
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Cyprien
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Hi!

The problem looks very simple. I want to impose a flux at the inlet of a domain. My solver is made of an advective-diffusive equation :

Code:
fvScalarMatrix TEqn
(
fvm::ddt(T) + fvm::div(phi,T) -fvm::laplacian(DT,T)
);
I know that I can get the corresponding flux from TEqn.flux()
Code:
surfaceScalarField phiT = TEqn.flux();
How can I impose a value to this flux at the inlet of my domain ? In that case, the BC velocity is non-zero and consequently the usual trick using fixedGradient can't work. I thought of something like
Code:
 phiT.boundaryField()[patchID] == Q;
but this doesn't work (of course...)

May be something like
Code:
  (TEqn.flux()).boundaryField()[patchID] == Q;
(but it doesn't compile...)

Is anybody has an idea ??

Best regards,
Cyp
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Old   March 28, 2012, 10:18
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Cedric Van Holsbeke
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Giving a calculated value to a boundary can be achieved using the codedFixedValue boundary condition (http://www.openfoam.org/version2.0.0...me-control.php).
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Old   March 28, 2012, 13:05
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Cyp
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Thank you for your reply.

Indeed I read the information about codedFixedValue, but I do not know how this can satisfy my request..

I think that imposing a flux should be a very easy thing in finite volume method..
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Old   May 22, 2012, 15:04
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Arne Stahlmann
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Hi Cyprien,

any progress so far? I'm struggling with the same problem for a couple of days now, but also have not yet found a way of directly imposing a flux. I need a flux and zero-flux boundary condition, but within the solver.

So far, in my case I could manage it with a source/sink term in the patch nearest cells, but that is not exactly what I wanted.

Greeting,
Arne
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