[elsebaer]

Hi everybody,


I have to include the term div(rho * dU & U) in a fvVectorMatrix, where & denotes the inner product of dU and U. The equation shall be solved for dU. I implemented the following code:

surfaceScalarField dPhi
(
    IOobject
    (
        "dPhi",
        runTime.timeName(),

        mesh,
        IOobject::READ_IF_PRESENT,
        IOobject::AUTO_WRITE
    ),
    fvc::flux(dU)

);


surfaceScalarField rhoDPhi(fvc::interpolate(rho)*dPhi);



fvVectorMatrix dUEqn.H
(
    ...
  + fvm::div(rhoDPhi & U)
    ...

);

I didn't get an error while compilation, but when I want to solve a test case, I get the following error:

incompatible fields for operation [dU] + [U]

In my opinion, this results from the fact, that the term fvm::div(rhoDPhi & U) causes OpenFOAM to think that U is the solution variable of the system instead of dU.


Do you have an idea how to "switch" dU and U in a mathematically correct way, without writing a new divergence operator?


Thanks a lot for thinking about this!