Unsteady kE with scalar transport - Outlet-geometry heavely effects scalar transport
 

Hi OpenFoamers,
I have a problem getting my custom OpenFOAM solver to transport scalar specie to the outlet!

I have tried several things:
1. It works with steadyState kE, solution converges and scalar is trasported.
2. It works as unsteady - if the outlet is a Ø80 tube and a pressure condition at the end! (no big opening)
3. I have tried symmetry BC, outletInlet BC and pressure Outlet BC for a square box
4. I have tried pressure Outlet BC for a half sphere.
5. I dont know why, but I have seen new variables in the time-folders U_0 and scalar_0 - why is there suddenly thees parallel files?
6. Residuals for specie are 1E-5
7. The falty solution seems to be caused by my outlet?

My custom code is like this:

fvScalarMatrix CH4Eqn
(
fvm::ddt(CH4)
+fvm::div(phi, CH4)
- fvm::laplacian(turbulence->nut()/0.7,CH4)
);
CH4Eqn.solve();

I use QUICK scheme for div and Euler for timestep.

I have attached jpegs of the current solutions.

Any suggestions?

BR Christian