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 galap February 14, 2013 05:44

Don't understand solver's behaviour

Hello guys,

today I'm facing a problem, which I can't explain. I have done a dummy calculation for a variable f. f is set everywhere to 1 (boundary/internal). Nevertheless OpenFOAM calculates values differing from 1. Can anyone explain that behaviour to me? Thank you very much in advance.

I have a normal transport equation for variable f:

Code:

```    f_(         IOobject         (             "f",             mesh.time().timeName(),             mesh,             IOobject::MUST_READ,             IOobject::AUTO_WRITE         ),         mesh     ),```
dimensions [0 0 0 0 0 0 0];

Boundary and internal values all set to 1.

Code:

```  multivariateSurfaceInterpolationScheme<scalar>::fielTable fields;     fields.add(f);     tmp<fv::convectionScheme<scalar> > convection     (         fv::convectionScheme<scalar>::New         (             mesh_,             fields,             phi,             mesh_.divScheme("div(phi,f)")         )     );```

So again keep in mind, for testing purpose I set all values to 1. Now I'm trying to solve the following equations:
Code:

```Info << "fmin/max  = " << min(f_).value() << ", " << max(f_).value() << endl;; tmp<fvScalarMatrix> fEqn (     fvm::ddt(rho, f_)     +  convection->fvmDiv(phi, f_)     -  fvm::laplacian(turbulence_->alphaEff(), f_) ); fEqn().relax(); solve(fEqn == rho* fSource);```
fSource is set to 0.

Code:

`Info << "fmin/max  = " << min(f_).value() << ", " << max(f_).value() << endl;;`
The Output is:

f min/max = 1, 1
f min/max = 0.90082369, 1.1320949

Schemes:

laplacian(alphaEff,f) Gauss linear corrected;
div(phi,f) Gauss upwind;

RASModel kEpsilon;

 galap February 14, 2013 06:05

solver used:

solver PBiCG;
preconditioner DILU;
tolerance 1e-7;
relTol 0.01;

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