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Modify dissipation equation

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Old   December 5, 2008, 21:27
Default Hi, I am trying to modify t
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Daniel Harlacher
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Hi,

I am trying to modify the dissipation equation in the standard kEpsilon model.

The problem is the following:

The dissipation equation looks like this:

// Dissipation equation
tmp<fvscalarmatrix> epsEqn
(
fvm::ddt(epsilon_)
+ fvm::div(phi_, epsilon_)
- fvm::Sp(fvc::div(phi_), epsilon_)
- fvm::laplacian(DepsilonEff(), epsilon_)
==
C1_*G*epsilon_/k_
- fvm::Sp(C2_*epsilon_/k_, epsilon_)
);

Instead of C1 I want to put:

fvScalarMatrix C1star = C1_+C1_*0.38*k_/epsilon_*1.0/(Gstar)*fvm::ddt(Gstar);

but it complains - from my understanding the variable types are not compatible G looks like this:

volScalarField G = nut_*2*magSqr(symm(fvc::grad(U_)));

and Gstar:

volScalarField Gstar = 0.5*magSqr(U_)+k_;

Has anyone an idea how I can make them compatible ? - the problem was, that 'fvm::ddt(Gstar)' only works in a fvScalarMatrix for me.

thanks
- harly
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Old   December 9, 2008, 10:07
Default Hi Harly! Have a look at th
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Bernhard Gschaider
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Hi Harly!

Have a look at the programmers guide section 2.4 (especially page 36): in order to get a source term for another equation you have to use the explicit form of the differential operators (in your case that might be fvc::ddt)

Bernhard
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