ENH: yPlus: add option to disable wall function contributions (#1773)

Summary

See the self-explanatory commit messages.

Resolved bugs (If applicable)

#1773

Details of new models (If applicable)

Small test cases: GL1773-pre-fix.zip vs GL1773-post-fix

Test-case characteristics:

• One-dimensional smooth-wall plane channel flow, ReTau=5200
• Number of cells = 20
• nu = 0.000192827 [m2/s]
• The case was designed to produce => -1*sqrt(mag(wallShearStress)) = 1
• The y1+ set (expected) = {0.05, 0.5, 1, 5, 10, 20, 30, 50, 100, 1000}
• kOmegaSST/SpalartAllmaras, simpleFoam

Main field of interest:

• mag(wallShearStress) function object returns ~ 1 for all test cases, therefore the expected y1+
• yPlus function object (min) results for lowerWall rounded up to 2 decimals:

y1+ = 0.05:

y1+ = 0.5:

y1+ = 1:

y1+ = 5:

y1+ = 10:

y1+ = 20:

y1+ = 30:

y1+ = 50:

y1+ = 100:

Risks

• Compiled with Gcc-7.4.1/Clang-9.0, DPInt32Opt
• No regression issue: 1-pre-fix-yPlus.zip vs 2-post-fix-yPlus.zip (Test: incompressible/pisoFoam/RAS/cavity)
• No changes in the default behaviour.
  • User can now select the new behaviour by useWallFunction=false which is by default true.