Force computation for compressible solvers uses p field

[MakisH]

As discussed in https://precice.discourse.group/t/multiphase-fsi-case-with-the-openfoam-adapter/1163/3, the force computation for compressible solvers seems to be using the p field.

This is fine in many cases, but can lead to issues in cases where the rgh part changes in the domain.

As a workaround, you can for now manually change p to p_rgh in your simulations, if needed.

Edit: This is only important in buoyant and multiphase solvers that account for hydrostatic pressure effects. These solvers compute everything based on p_rgh and p is only a derived quantity for them, which may lead to strange issues.