heat flux boundary condition multiphase flow
 

This is with reference to openfoam 2.3

How can one specify constant heat flux BC for multiphase flows;

For single phase flows, fixedGradient BC can be specified (where the gradient is heatFlux/thermalConductivity)

However, in multiphase flows (eulerian or interFoam with TEqn), the alpha (volumeFraction) on the wall is not equal to 1 in many cases when a bubble or droplet comes in contact with the heated wall temporarily, and hence, an alpha-dependant BC must be specified - something like

gradient = heatFlux / (alpha1*k1 + (1-alpha1)*k2)

could this be accomplished using the standard BCs or should one use a groovyBC.

using a groovyBC like this,

b_heater
{
type groovyBC;
refValue uniform 293.15;
gradientExpression "qflux/kAlphaEff";
variables "qflux=10000;kAlphaEff=alpha1*0.5+(1.0-alpha1)*0.02;";
// value uniform 293.15;
}

I get the error message shown in the attached file.

however, if I change the groovyBC to exclude alpha1 from the expression (by using dummy values=0.5) like below:

b_heater
{
type groovyBC;
refValue uniform 293.15;
gradientExpression "qflux/kAlphaEff";
variables "qflux=10000;kAlphaEff=0.5*0.5+(1.0-0.5)*0.02;";
// value uniform 293.15;
}

the simulation runs without errors.

How can this be resolved ?

Thanks.