The NACA airfoils are airplane wing shapes developed by the National Advisory Committee for Aeronautics (NACA). These shapes are described by a series of digits, which are translated into actual shapes by a series of computer programs. These programs date back several decades, and were written in Fortran.

BRL-CAD's interest in this code is as a possible means of procedurally generating wing geometry in BRL-CAD models, but we would prefer to have the shape generating logic in one of BRL-CAD's standard languages - C or C++. The target code for this effort is a modernization of older NACA codes by Ralph Carmichael called naca456.

The initial conversion will attempt to precisely reproduce the functionality as currently expressed in the Fortran code - any more elaborate reworking of the logic will be evaluated after we have a C/C++ version that reproduces the Fortran outputs correctly.

This task depends on the successful completion of tasks #1 - #3 - this file makes use of the files from those tasks. Students shouldn't claim (and mentors shouldn't assign) this task until the others are complete.

Your task involves converting the file https://github.com/starseeker/naca/blob/master/naca456.f90 to C++.

1. Check out the git repository: git clone https://github.com/starseeker/naca
2. Make sure you can build the stub files that are there (cd naca; mkdir build; cd build; cmake ..; make)
3. Translate the logic in naca456.f90 into naca456.cxx
4. Make sure the code compiles (it will not be expected to do anything at this stage.)
5. Submit the new .cxx file. (If you are comfortable doing so, you can fork the project on github, do your work in the fork, and submit a github pull request instead - either approach is fine.)

You'll want to make sure to preserve any comments that contain useful information from the Fortran sources, as well as the actual logic. If you're successful, there will be follow-on tasks building on this one to compare the output of the new C++ naca456 to the original Fortran version.

• http://www.pdas.com/naca456.html
• https://github.com/starseeker/naca