[open]

Hi all,

Working on a problem with non-Newtonian shear thinning materials. It is expected (cf. experiments) that the outlet velocity is substantially increased (order of 20-50 %) in response to interaction with high shear rate objects. By this I mean oscillating wall or similar.

However in all the cases I've tried so far (2D, 3D, oscillating walls, oscillating velocity BC; pimpleDyMFoam, nonNewtonianIcoFoam) the outlet velocity tends to equalize with the inlet velocity (1 m/s). I'm not anticipating mesh problems since checkMesh passes and the geometry is a rectangular channel. What are the appropriate boundary conditions to permit shear thinning velocity increases?

Example:

U

    wInlet
    {
        type            pressureInletVelocity;
        value           uniform ( 0 0 0 );
    }

    wOutlet
    {
        type            pressureInletOutletVelocity;
        value           uniform ( 0 0 0 );
    }

    wWall
    {
        type            oscillatingFixedValue;
        refValue    uniform ( 0 0 -1 );
        offset          ( 0 0 1 );
        frequency    40;
        amplitude    0.156078;
    }

P

wOutlet
    {
        type            fixedValue;
        value           uniform 0;
    }

    wInlet
    {
        type            fixedValue;
        value           uniform 9810; // rho*g
    }

    wWall
    {
        type            zeroGradient;
    }

transportModel  powerLaw;

powerLawCoeffs
{
    nuMin        nuMin [ 0 2 -1 0 0 0 0 ] 1e-4; 
    nuMax        nuMax [ 0 2 -1 0 0 0 0 ] 4;
    k               k [ 0 2 -1 0 0 0 0 ] 0.04; // k/rho k=40
    n               n [ 0 0 0 0 0 0 0 ] 0.3;
}

   rho rho [1 -3 0 0 0 0 0 ] 1000.0;

dt~1e-8 (variable)