CFD Online Discussion Forums - Multispecies jet flow in a garage, HELP !!

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)

- OpenFOAM (http://www.cfd-online.com/Forums/openfoam/)

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

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 !!

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()

                )

            )

        );

    }

Hi,

Have you looked into twoLiquidMixingFoam?

Pei

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