CFD Online Discussion Forums - Making density dependent on concentration

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Making density dependent on concentration

Hello,

My current solver is based on the incompressible pimpleFoam, in which I've added a solver for solute concentration C:

Code:

solve

    (

    fvm::ddt(C)

    + fvm::div(phi, C)

    - fvm::laplacian(Diff, C)

    );

Now, I would like to have the fluid density depend on the solute concentration according to:

Code:

rho = base_value + rho_factor * C

Not having much experience with OpenFOAM, I'm a bit in the dark about how to go about implementing this. I can't claim to fully understand the compressible solvers I've looked at yet, but I'm not sure I have to go there either? Already having the C field in place, it shouldn't be neccesary to create a rho field as well? given the simple relation that is.

Currently, the momentum equation is solved as follows:

Code:

tmp<fvVectorMatrix> UEqn

(

    fvm::ddt(U)

  + fvm::div(phi, U)

  + turbulence->divDevReff(U)

);

Basically, the question is, how do I go about implementing this? any hints or help would be appreciated!

Have a look at settlingFoam, which implements a solver for the transport of solid particles in an incompressible fluid by means of a mixture model. The description of the solver can be found in Brennan's thesis. Maybe these resources will inspire you :)

I've been going through settlingFoam, however I'm still having difficulties getting this to work - whatever approach I take, I end up with a dead-end. This seems like something that should be simple to implement? Any more help would be appreciated..