XY plane anti-symmetry

[tomaso909]

Is your feature request related to a problem? Please describe.
A symmetry option for the x-y plane would allow the simulation of ground effect. I guess that a possible workaround is to just define an additional wing/plane that is a symmetry of the base one.

However, I need an anti-symmetry option for the x-y plane. The difference with the symmetry (slip wall) is that in the anti-symmetry case Cp is constant. This basically simulates a free-surface (e.g. sea surface) and therefore would open the door to using MachUpX for simulating hydrofoils. I believe there is no workaround for the anti-symmetry approach and the code has to be modified.

AVL does support the anti-symmetry approach (see iZsym option): http://web.mit.edu/drela/Public/web/avl/avl_doc.txt
However MachUpX is much easier to integrate in my workflow.

I think it should be a relatively simple feature to add for someone familiar with the code. As far as I understand, an anti-symmetry is the same as a symmetry but in this case the matrix of coefficients is inverted for the symmetric part. So basically, the matrix of control points of the wing has to be mirrored across the XY plane (symmetry) and then the matrix of coefficients has to be inverted for those points only. The effect of the anti-symmetry in the general circulation is taken into account but the forces for the mirrored part have to be discarded.

If the feature is implemented I am happy to perform a validation with commercial CFD software (StarCCM+) and share it here.

Describe the solution you'd like
Ideally there would be an anti-symmetry option in the input .json file. I guess that implementing an XY symmetry option is a necessary intermediate step so it will be done anyway and an option could also be added in the .json file.

Describe alternatives you've considered
As I mentioned, there is a workaround for the symmetry case, however the anti-symmetry requires some code changes.

Additional context
See AVL documentation: http://web.mit.edu/drela/Public/web/avl/avl_doc.txt

[corygoates]

We've had this request before. It would definitely not be trivial to add and would take some time. Unfortunately, this is not a lab priority, and we do not have time/funding for this currently. I'll keep the issue open though in case we do end up having some availability for implementing this.