Proposed Changes

This pull request restricts the use of the FLUID_MIXTURE model only when the KIND_SCALAR_MODEL is SPECIES_TRANSPORT.

Related Work

Reported in CDF-Online
https://www.cfd-online.com/Forums/su2/257519-kind_scalar_model-mixture.html

PR Checklist

Put an X by all that apply. You can fill this out after submitting the PR. If you have any questions, don't hesitate to ask! We want to help. These are a guide for you to know what the reviewers will be looking for in your contribution.

• [ x] I am submitting my contribution to the develop branch.
• [ x] My contribution generates no new compiler warnings (try with --warnlevel=3 when using meson).
• [ x] My contribution is commented and consistent with SU2 style (https://su2code.github.io/docs_v7/Style-Guide/).
• I used the pre-commit hook to prevent dirty commits and used pre-commit run --all to format old commits.
• 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.