Add upwinding option to Richards FV solver
The following discussion from !132 (merged) should be addressed:
Maybe create a new
RichardsFVUpwindinghere, like for the DG operator? Would be great to control this via the config file, especially because upwinding is much more important for FV (right...?).
Well, the usual upwinding (as far as I know) just that easy: Select the conductivity based on the direction of flux.
Nope, the usual upwinding is to upwind the conserved quantity with respect to an advective force (e.g., water flux in the case of solute transport)
Upwinding is a common technique for stabilizing the finite volume method. An option for selecting it like in the DG might be useful. However, I have not run into any stability issues with the FV solver yet. Infiltration fluxes higher than the saturated conductivity can turn the Richards equation hyperbolic, resulting in a very stiff problem. But the FV solver seems to deal with this just fine (although I admittedly only ran very few tests).
- Check back with Ole how upwinding should be implemented in case of the Richards FV solver (upwind conductivity or flux) or if it is necessary at all.
- Implement an upwinding option through the config file.
How to test the implementation?
Add upwinding case to ODE tests.
#159 (closed): Fix signs in upwinding query (follow-up)