[Edy]

Hi Foamers,

I am developing a Euler-Euler solver for two-phase flow. For the moment I only consider an adiabatic case and no interfacial area concentration transport equation (IACTE). [At a later stage, I will implement boiling and IATCE but this is not my goal right now]

I implemented the following interfacial forces :
- Ishii Zuber drag
- Zuber virtual mass
- Gosman (Favre averaged) turbulent dispersion
- Tomiyama lift
- Tomiyama wall lubrication

My case is based on the DEDALE experiment performed at EDF, which consists of a upwards water flow in a vertical pipe, in which is injected gas bubbles. No heating is applied. I even makes it simpler cause i consider basically a 2D channel instead of a 3D pipe.

However, my wall lubrication force seems to be wrong cause for 0.6 mm diameter bubbles, i do not observe wall peaking (the void fraction is maximum at the wall, like if the wall lubrication force was not big enough to countereffect the lift). Then I tried to run a new simulation for 2mm diameter bubbles and my code crashed after 0.002s of simulation, the wall lubrication force had tremendously increased and made the gas velocity explode (500 m/s).

I am a bit confused about this Tomiyama wall lubrication force. Concerning the relative velocity which is needed for its calculation, is it the relative velocity for each local cell, or at the centerline location? Should it be the total magnitude of the relative velocity or only the part in the flow direction?

Here is what I implemented for this force :

volScalarField AWallLubrication = wallLubricationa->AWL(alpha,DS,magUr);  //calls a

volVectorField wallLubricationForce = AWallLubrication*(1/pow(distToWall,2)-1/pow(D-distToWall,2))*normal

// I checked distToWall and D (the pipe diameter) and these fields are OK so the pb might be in AWL

The function AWL is defined in the Tomiyama wall lubrication class as following :

dimensionedScalar g
    (
        "g",
        dimensionSet(0, 1, -2, 0, 0, 0, 0),
        scalar (9.81)
    );

    volScalarField Eo = mag(g)*(phaseb_.rho()-phasea_.rho())*pow(DS,2.0)/phaseb_.sig();
    volScalarField CwlEo = exp(-0.933*Eo+0.179);

    forAll(Eo, celli)
    {
        if (Eo[celli] < 1.0)
        {
            CwlEo[celli] = 0.47;
        }
        else if (Eo[celli] >= 1.0 && Eo[celli] <= 5.0)
        {
            CwlEo[celli] = exp(-0.933*Eo[celli]+0.179);
        }
        else if (Eo[celli] > 5.0 && Eo[celli] <= 33.0)
        {
            CwlEo[celli] = 0.00599*Eo[celli]-0.0187;
        }
        else if (Eo[celli] > 33.0)
        {
            CwlEo[celli] = 0.179;
        }
    }

    return 0.5*CwlEo*phaseb_.rho()*pow(Ur,2.0)*DS;  //DS is the bubble diameter

Has anyone already implemented Tomiyama wall lubrication force? Or see what might be wrong in my implementation? Any other idea, suggestion is welcome.

Thanks in advance.
Best,


/Edy