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Old   November 25, 2009, 08:23
Default Source terms in equations
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Kapa Lilla
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Dear All,

I try to add source terms in all the equations in coodles. When I add one to the density - so to the continuity equation - I found a rather strange behaviour. I printed out the magnitude of my source term from the function it calculates and from the solver itself (like rhoEqn.source()). Good news, they coincide. On the other hand:

diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0

It seems that the sources computed and assigned, but during the iterations they are not considered.

Can anyone help me on this issue?

Thanks,

Lilla
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Old   November 25, 2009, 08:35
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Niklas Nordin
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If you're adding a source term to the continuity equations dont forget the addition to the PISO loop.
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Old   November 25, 2009, 08:39
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Kapa Lilla
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I did modify it as well. Unfortunatelly.
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Old   November 26, 2009, 06:40
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Kapa Lilla
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I've performed an other test as well. Now with the original OF solver, so without source terms. It is a cavity flow. In fact the simulation is running, and the results seems meaningful. But I still have that funny line:

diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0

Have anyone idea why is it like that?

Thanks,

Lilla
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Old   November 26, 2009, 06:56
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because your matrix is purely diagonal.

fvm::ddt(rho) + fvc::div(phi) = S

produces a matrix-vector system like A*rho = H

and if A dont have any offdiagonal elements you can solve for rho exactly in 1 iteration.
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