[Roie_E]

Dear FOAMers,

I have a problem with a boundary condition for a diffusive scalar field I added to my BouyantBoussinesquPimpleFOAM solver.
I have a 2D tank filled with the scalar field C which settling at a constant velocity (using a modified flux I called "phiC" which has a uniform downward component of velocity).

I want this field to simply pass through the bottom of the tank without accumulating. I figured this should be done using Advective boundary condition, but looks like just above the bottom the field still accumulates.

I attach here the profile of the C field and a "plot over line" in the vertical direction of it, so the accumulation at the bottom could be visible.
In another image I attach a zoom-in of the bottom to emphasize the effect:




The 0/C file looks like this:
dimensions [0 0 0 0 0 0 0]; // salt crystals is dimless

internalField uniform 1;

boundaryField
{

top
{
type zeroGradient;
}

left
{
type zeroGradient;
}
slope
{
type advective;
phi phiC;
}
bottom
{
type advective;
phi phiC;
}
right
{
type zeroGradient;
}
defaultFaces
{
type empty;
}

}


Does anyone know why I get this accumulation?

Thanks,
Roie