Fix sign error in incompressible Spalding wall function

[dunapkt]

Proposed Changes

Fix a sign error in the Spalding wall function term in INC_NSSolver.cpp. The constant '+1.0' is changed to '-1.0' to match Spalding(1961) and Nichols & Nelson (2004). I've also checked the derivatives, but there were no issues.

Related Work

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.

• I am submitting my contribution to the develop branch.
• My contribution generates no new compiler warnings (try with --warnlevel=3 when using meson).
• 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.

[bigfooted]

Looks like in the incompressible flow implementation, the minus sign is wrong.
The reference from Nichols and Nelson:

[bigfooted]

The regression tests for the wall functions fail now and have to be updated. Can you do this?

You have to go to Testcases/serial_regression.py
and then these lines:

inc_turb_wallfunction_flatplate_sa.test_vals = [-6.894206, -5.715970, -6.743740, -4.242551, -9.550272, 10.000000, -2.879370, 0.001021, 0.003759]
The new values according to the checks are:
inc_turb_wallfunction_flatplate_sa.test_vals = [-6.894226, -5.716031, -6.743814, -4.242551, -9.550079, 10.000000, -2.879412, 0.001021, 0.003759]

Same for:

inc_turb_wallfunction_flatplate_sst.test_vals = [-6.881306, -5.729111, -6.724803, -4.242636, -7.162846, -2.044959, 10.000000, -2.877924, 0.001151, 0.003161, 0.000000]
new values are:
inc_turb_wallfunction_flatplate_sst.test_vals = [ -6.881321, -5.729177, -6.724837, -4.242636, -7.162893, -2.044945, 10.000000, -2.877955, 0.001151, 0.003161, 0.000000]

and in Testcases/Tutorials.py:

sudo_tutorial.test_vals = [-14.664419, -12.789769, -13.280336, -13.016392, -13.018817, -9.510066, 15.000000, -1.994192]
New values are:
sudo_tutorial.test_vals = [-10.243992, -8.397140, -8.812974, -8.525505, -8.731439, -5.183918, 15.000000, -1.941343]

[dunapkt]

I've completed all the updates you requested. Let me know if anything else needs adjusting

[bigfooted]

LGTM