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-   -   Multispecies jet flow in a garage, HELP !! (http://www.cfd-online.com/Forums/openfoam/76399-multispecies-jet-flow-garage-help.html)

Pierre Mathieu May 25, 2010 04:36

Multispecies jet flow in a garage, HELP !!
 
Hi everyone,

I want to simulate the injection of Helium into air in a confined space, and I am quite new with OpenFoam.

I used the reactingFoam solver adding the gravity effect (rho*g) to the velocity equation (UEqn.H) but my results are bad : my species are mixing like if there was no buoyancy effects between them...

I want to figure the density effects between the species during the injection.

If someone have some advices to give, I would be grateful.
Thank you !!

eelcovv May 27, 2010 11:04

Hi Pierre,

Perhaps you can use something simular as buoyantBoussinesqPisoFoam, which means you only solve one phase (air) and solve helium as a passive scalar A mixing into the room with A=1 at inlet and A=0 at t=0 in the room. Solve the transport of A and add a momentum source to your U equation based on the fraction of helium in air (just a the boussinesq equation). Something like below, but I haven't checked it, so probably needs some adjustments. Goodluck

To solve transport of A (helium fraction)
Code:

{
    volScalarField kappaEff
    (
        "kappaEff",
        turbulence->nu()/Pr + turbulence->nut()/Prt
    );

    fvScalarMatrix AEqn
    (
        fvm::ddt(A)
      + fvm::div(phi, A)
      - fvm::laplacian(kappaEff, A)
    );

    AEqn.relax();

    AEqn.solve();

    rhok = (rho_air-rho_hel)/rho_air*A;

and to solve U

Code:

    fvVectorMatrix UEqn
    (
        fvm::ddt(U)
      + fvm::div(phi, U)
      + turbulence->divDevReff(U)
    );

    UEqn.relax();

    if (momentumPredictor)
    {
        solve
        (
            UEqn
        ==
            fvc::reconstruct
            (
                (
                    fvc::interpolate(rhok)*(g & mesh.Sf())
                  - fvc::snGrad(p)*mesh.magSf()
                )
            )
        );
    }


phsieh2005 May 27, 2010 14:08

Hi,

Have you looked into twoLiquidMixingFoam?

Pei

Pierre Mathieu May 28, 2010 10:33

Hi,

I am actually trying with twoLiquidMixingFoam, I am waiting for the results.

Thanks for the advices Eelco, I wil try this way too!
Pierre


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