CST airfoil parameterization

[eytanadler]

Purpose

This PR adds a CST parameterization for airfoil optimization. It allows for design variables of the CST parameters, class shape, and chord length. All derivatives analytically defined.

Expected time until merged

2 furlongs

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

Tests for the new DVGeometryCST can be found in tests/reg_tests/test_DVGeometryCST.py.

Checklist

• I have run flake8 and black to make sure the code adheres to PEP-8 and is consistently formatted
• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[eytanadler]

Not sure what's going on with flake8, but it must be due to a new version since it's from code I didn't touch. What's the best approach to handle that?

[ewu63]

Not sure what's going on with flake8, but it must be due to a new version since it's from code I didn't touch. What's the best approach to handle that?

Yeah this is from flake8-bugbear which just had a new version released. It gets a bit tricky pinning versions of all packages but I guess we could do it. Though for this kind of thing new versions bring better bug detection.

[eytanadler]

Not sure what's going on with flake8, but it must be due to a new version since it's from code I didn't touch. What's the best approach to handle that?

Yeah this is from flake8-bugbear which just had a new version released. It gets a bit tricky pinning versions of all packages but I guess we could do it. Though for this kind of thing new versions bring better bug detection.

Got it. I'm happy to fix it in this PR, I'm just not exactly sure what it needs. I tried adding a nonlocal, but that didn't do it.

[ewu63]

Yeah at first glance I'm not really sure either. If we can't figure it out we can always tell flake8 to skip the warning.

[anilyil]

Looking a lot better. few issues left

[anilyil]

It looks like the flake check is complaining that the twist function defined in the dvgeomulti test can vary with different axes. Especially, the nrefaxis variable there might be getting updated, or there's a risk of it. we can just add it as an optional parameter to the function and set the value when we define the function. maybe that way it wont complain. sth like:

            # Set up a twist variable
            def twist(val, geo, nRefAxPts=nRefAxPts):
                for i in range(1, nRefAxPts):
                    geo.rot_z["box"].coef[i] = val[i - 1]

I don't know if this will fix it though.

[eytanadler]

It looks like the flake check is complaining that the twist function defined in the dvgeomulti test can vary with different axes. Especially, the nrefaxis variable there might be getting updated, or there's a risk of it. we can just add it as an optional parameter to the function and set the value when we define the function. maybe that way it wont complain. sth like:

            # Set up a twist variable
            def twist(val, geo, nRefAxPts=nRefAxPts):
                for i in range(1, nRefAxPts):
                    geo.rot_z["box"].coef[i] = val[i - 1]

I don't know if this will fix it though.

Nice! Looks like this did the trick

[anilyil]

Looks good. Thanks for working on the changes