AD: add new projection method and BEM methods

[ebranlard]

This pull request is ready to be merged. It has been reviewed by @bjonkman.

Feature or improvement description To help the development of new BEM algorithms, with different projection methods and implementations, some flags are introduced to the AeroDyn code. The flags are currently "hidden" to the user, as we need more time to decide on the implementation, document it, and add tests. In the long term, this version should have limited code differences with Envision's version.

Impacted areas of the software AeroDyn

Additional supporting information Two main toggles are introduced

• “AeroProjMod” to distinguish between the different coordinate system used: o APM_BEM_NoSweepPitchTwist=1 "Original AeroDyn model where momentum balance is done in the WithoutSweepPitchTwist system" o APM_BEM_Polar=2 "Use staggered polar grid for momentum balance in each annulus" o APM_LiftingLine=3 "Use the blade lifting line (i.e. the structural) orientation (currently for OLAF with VAWT)"
• “BEM_Mod” to switch between different BEM implementations: o BEMMod_2D=0 "2D BEM assuming Cx, Cy, phi, L, D are in the same plane" o BEMMod_3D=2 "3D BEM assuming a momentum balance system, and an airfoil system"

The BEM time integration now uses the standard "utimes" vector instead of indices 1 and 2 which were hardcoded.

The coordinate system "withoutSweepPitchTwist" is now renamed orientationAnnulus, and of type R8Ki.

Test results, if applicable Test should match.

Checklist

• [ ] potentially wait for #957

[ebranlard]

Hi @bjonkman

These outputs are indeed a bit confusing with the different coordinate systems. Thank you for this careful review!