[leroyv]

Dear OpenFOAM users,
I recently wrote a simple custom boundary condition which computes the fluid velocity at the wall using a formula of the type:

v = f(rho) * normal

While my code yields the expected results using the rhoPimpleFoam solver, everything is messed up when using it with chtMultiRegionFoam, even though I use the exact same parameters for the BC. The near-wall velocity has an inverted orientation, and the upstream flow has a stagnation point, even if the wall velocity is oriented downstream. This is obviously a physical and numerical nonsense ...

Is there something in particular that should be taken care of when using chtMultiRegionFoam with custom BCs?

Parameters with rhoPimpleFoam:

squareWall
    {
        type            pyrolysisVelocity;
        refValue        0.001;
        massPR          0.001;
        rhoS            -1;
        rhoName         rho;
    }

Result: https://www.dropbox.com/s/n7cfws80w3...Foam_outer.png

With chtMultiRegionFoam:

fluid_to_solid
            {
                type pyrolysisVelocity;
                refValue 0.001;
                massPR 0.001;
                rhoS -1;
                rhoName rho;
            }

Result: https://www.dropbox.com/s/8t2re4piih...Foam_outer.png

[leroyv]

A little progress update: I went through the code and did some additional debugging. The coordinates of velocity on the patch seem to be computed correctly: I checked the values in the output files.

The results with a surfaceNormalFixedValue BC are okay:
https://www.dropbox.com/s/zui2qaz9tz...FixedValue.png
I'm guessing something wrong happens when running the updateCoeffs() method, maybe I shouldn't use the fixedValueFvPatchVectorField::operator==() member function?

[leroyv]

I ran an additional test using swak4foam:

fluid_to_solid
    {
        type groovyBC;
        valueExpression "- 0.001 * normal()";
    }

It gave nearly the same result as obtained with chtMultiRegionFoam:
https://www.dropbox.com/s/0yjr5vca1y..._swak4foam.png

[leroyv]

I computed the mass flux using the patchIntegrate utility.

Solver: chtMultiRegionFoam (using BCs for isothermal flow)
Inlet mass flux: 0.000811 kg/s

1. BC: surfaceNormalFixedValue, -0.001
fluid_to_solid mass flux: 0.000463 kg/s
Outlet mass flux: 0.00127 kg/s

2. BC: groovyBC, "- 0.001 * normal()"
fluid_to_solid mass flux: <something>e-20 = 0 kg/s
Outlet mass flux: 0.000811 kg/s

Mass conversation seems to be okay. Something might be going wrong with the phi field, because the value of U at the boundary seems to be fine:

        value           nonuniform List<vector>
40
(
(0.001 0 0)
(0 -0.001 0)
(0.001 0 0)
(0.001 0 0)
(0.001 0 0)
(0.001 0 0)
(0.001 -0 0)
(0.001 -0 0)
(0.001 -0 0)
(0.001 -0 0)
(0.001 -0 0)
(0 0.001 0)
(0 -0.001 0)
(0 0.001 0)
(0 -0.001 0)
(0 0.001 0)
(0 -0.001 0)
(0 0.001 0)
(0 -0.001 0)
(0 0.001 0)
(0 -0.001 0)
(0 0.001 0)
(0 -0.001 0)
(0 0.001 0)
(0 -0.001 0)
(0 0.001 0)
(0 -0.001 0)
(0 0.001 0)
(-0.001 -0 0)
(0 -0.001 0)
(-0.001 -0 0)
(-0.001 -0 0)
(-0.001 -0 0)
(-0.001 -0 0)
(-0.001 0 0)
(-0.001 0 0)
(-0.001 0 0)
(-0.001 0 0)
(0 0.001 0)
(-0.001 0 0)
)

Any idea of what that could be? I attached my case directory.