Proposed Changes

@jtneedels and I have worked on implementing the Air-7 gas model to the NEMO native fluid model. This allows for simulations of inviscid weakly ionized flows with the addition of NO+ and e-.

I am open to adding a test case for this, similar to the thermal bath case, since they run extremely fast, though I am open to idea.

Work is ongoing to extend this viscous simulations.
Updates from #1533 are added here as well.

PR Checklist

• I am submitting my contribution to the develop branch.
• My contribution generates no new compiler warnings (try with the '-Wall -Wextra -Wno-unused-parameter -Wno-empty-body' compiler flags, or simply --warnlevel=2 when using meson).
• My contribution is commented and consistent with SU2 style.
• I have added a test case that demonstrates my contribution, if necessary.
• I have updated appropriate documentation (Tutorials, Docs Page, config_template.cpp) , if necessary.