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Old   November 2, 2013, 16:08
Default porosity and buoyancy
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Robert
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Hi there,

has anyone of you ever successfully set up a case with a porosity zone, using chtMultiRegionFoam or at least any solver that solves for p_rgh instead of p?

You might have notices from the large amount of threads I have posted on this topic, that I have already had a hard time trying to do so and I finally got to the point of saying: it simply won't work with openfoam.

I hope there's someone out there who disagrees with my opinion - and maybe is able and willing to help.

Best,

Robert
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Old   November 4, 2013, 05:00
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I think I may have found the reason for chtMultiRegionFoam not working with an explicitPorositySource in the fvOptions file.

In the UEqn.h fvOptions(rho, U) usually is added to the rhs (e.g. in chtMultiRegionSimpleFoam and rhoPimpleFoam). In the UEqn.h of chtMultiRegionFoam, fvOptions(rho, U) is added to the left hand side, which should mean it has the opposite effect. Now the strange pressure behaviour along the probe seems quite reasonable to me.

I think this is a bug, what do you think?
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Old   November 4, 2013, 06:35
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It works! For those who want to use explicitPorositySource with chtMultiRegionFoam, you have to change

tmp<fvVectorMatrix> UEqn
(
fvm::ddt(rho,U)
+ fvm::ddt(phi,U)
+ turb.devDevRhoReff(U)
+ fvOptions(rho,U)
);

to

tmp<fvVectorMatrix> UEqn
(
fvm::ddt(rho,U)
+ fvm::ddt(phi,U)
+ turb.devDevRhoReff(U)
==
fvOptions(rho,U)
);

and the porositySource works properly.
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