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- - Solve dS_dt + div(vect(U)*f(S))=q (https://www.cfd-online.com/Forums/openfoam/75591-solve-ds_dt-div-vect-u-f-s-q.html)

Solve dS_dt + div(vect(U)*f(S))=q

Hi
I am trying to solve this equation in openfoam.

dS_dt + div(vect(U)*f(S))=q

where f(S) is a known equation dependent of S. S cannot be explicitly extracted from f(S).

up to now if I implement the equation as stated above I get an error concerning calculatedFvPatchField.

Has anybody had similar problems?

Thanks

Andres

A bit vague :-)

You should give some more detail on how the equation was implemented, and be specific with the error message.

Best,

Hi Alberto,

I hope that the problem declaration this time is more illustrating.

Implementation:

The initial values of

Code:

volScalarField S

volVectorField U

are read from the case directory 0 and

Code:

dimensionedScalar const1

dimensionedScalar const2

from the constant directory.

The implementation reads

Code:

    volScalarField X = (S-const1)/(const2);

    f = pow(X,2)/(2*pow(X,2)-2*X-1);



    phi = linearInterpolate(U) & mesh.Sf();

    fvScalarMatrix SEqn

        (

            por*fvm::ddt(S) +

            fvm::div(phi,f) ==

            q

        );

        solve(SEqn);

Code:

Error: 



--> FOAM FATAL ERROR: 



    valueInternalCoeffs cannot be called for a calculatedFvPatchField

    on patch fixedWalls of field f in file "/home/i/andres/Simulations/FOAM/darcy2/0/f"

    You are probably trying to solve for a field with a default boundary condition.



    From function calculatedFvPatchField<Type>::valueInternalCoeffs(const tmp<scalarField>&) const

    in file fields/fvPatchFields/basic/calculated/calculatedFvPatchField.C at line 145.

I am no very sure what this means. Do I need to create my own boundary condition to fulfill this? or can I define my equation in another way ?

Thanks

Andres

try to replace
fvm::div(phi,f)
with
fvc::div(phi,f)

You cant solve implicitly for both f and S, they arent really the same fields are they?