Calculate buoyancy for an MHK turbine

[hkross]

This pull request is ready to be merged.

Development is complete and all existing regression tests pass. New regression tests have been added, along with baselines. A corresponding pull request (#55) has been added to my r-test repository.

Feature or improvement description

This pull request allows buoyant loads on a marine hydrokinetic turbine to be calculated and adds the following features:

• Buoyancy parameters for the blade, tower, hub, and nacelle added to the AeroDyn blade and primary input files
• Buoyancy flag added to the AeroDyn primary input file
• Buoyant loads on the blade, tower, hub, and nacelle calculated in AeroDyn and added to existing loads
• Hub and nacelle loads passed to ElastoDyn (glue code changes for nacelle included in prior pull request)
• Outputs added for buoyant loads
• Outputs denoted as 'Aero' changed to 'Fld'

Impacted areas of the software

• AeroDyn module
• AeroDyn driver
• OpenFAST glue code

Test results

All existing regression tests have been updated and pass. New regression tests have been added, including input files and baselines.

Check list

• Fix glue code bug (see section below)
• Merge in [BugFix] Nacelle position set inconsistently by glue code and AeroDyn driver #1009
• Update docs/source/user/api_change.rst
• Update documentation
• Merge in Enable cavitation calculation and outputs using FVW #1078

Additional supporting information

Update: This bug was fixed by this pull request.
There is a bug in the glue code changes that prevents test cases from converging when buoyancy is turned on. Cases only converge if all degrees of freedom are turned off in ElastoDyn (with the exception of the blades) or if the new code in FAST_Solver.f90 that transfers hub loads from AeroDyn to ElastoDyn is commented out (line 381).

[ebranlard]

My small comments here would be:

• I've added some backward compatibility so that blade files without Buoyancy inputs can still be read
• I would be in favor of having the nacelle NacCenBx,y,z inputs to be on one line instead of 3
• I would place the Hub and Nacelle inputs above the tower, to have the inputs in that order: Blades > Hub > Nacelle > Tower

I'm eager to get this pull request in, so I can take care of some changes if needed.

[hkross]

My small comments here would be:

• I've added some backward compatibility so that blade files without Buoyancy inputs can still be read
• I would be in favor of having the nacelle NacCenBx,y,z inputs to be on one line instead of 3
• I would place the Hub and Nacelle inputs above the tower, to have the inputs in that order: Blades > Hub > Nacelle > Tower

I'm eager to get this pull request in, so I can take care of some changes if needed.

Thanks, @ebranlard. I can take of the input file changes for this if you can make the code modifications. Would that work?

[ebranlard]

No worries, I'm happy to do all of it.
Do you think the changes would make sense? I'm waiting for @jjonkman feedback as well.

[hkross]

I am fine with either option for both the NacCenBx,y,z inputs and the order of inputs for the tower, hub, and nacelle. The main motivation for putting the hub/nacelle inputs after the tower was that hub/nacelle inputs are only relevant for MHK turbines, whereas the tower inputs are more generally used. So, it made sense to me to have them after the tower since they will more often be neglected. But, I am fine with having it either way.

[ebranlard]

I guessed so, in the future we can add aerodynamics loads on the nacelle, that's why I think it makes sense to have it higher up.

[ebranlard]

I will take care of the changes

[jjonkman]

I approve this PR. I heard from @hkross that her recent changes to the buoyancy calculation solved the problem with residual moments that was delaying the merge of this pull request.

See two minor comments on the documentation below, which I assume can be easily addressed before merging.

I agree with moving the hub and nacelle inputs up, between the blade and tower inputs before merging. This will make more sense once hub and nacelle aerodynamics are added to AeroDyn in the future.

I don't have a strong preference whether NacCenBx,y,z is one line or three in the input file.

Looking forward to getting this new functionality merged in!

[hkross]

I will take care of the changes

Thanks, @ebranlard. I can take care of the documentation changes @jjonkman suggested.

[hkross]

@ebranlard I changed a couple small things in the documentation. Otherwise, all the changes look good.