Fix ForcingAbsorption (Sponge layer) for 2.5D simulations

Issue/feature addressed

Using the ForcingAbsorption for dampening the flow in a certain region of the domain was not working properly for 2.5D simulations. It did apply the absorption in non-WaveSpace while the solution was in WaveSpace.

Proposed solution

Added detection of homogeneous expansions during initialisation and an additional HomogeneousFwdTrans for the absorption forcing to be in WaveSpace.

Implementation

See Proposed solution

Tests

• Kovasznay flow where the sponge should essentially apply the exact solution. This would cause a high error prior to the fix.

Suggested reviewers

@CFD-Xing @ssherw

Notes

• This has only been tested with the IncNavierStokesSolver, because the issue popped up here.

Checklist

• Functions and classes, or changes to them, are documented.
• [ ] User guide/documentation is updated.
• Changelog is updated.
• Suitable tests added for new functionality.
• Contributed code is correctly formatted. (See the contributing guidelines).
• [ ] License added to any new files.
• No extraneous files have been added (e.g. compiler output or test data files).