BUG: fix yPlus predictions of nut wall functions

Summary

• Corrects y+ predictions from nutUWallFunction, nutkWallFunction and nutLowReWallFunction, but the internal y+ predictions of these wall functions were kept the same in order to keep their nut predictions the same.

Resolved bugs

Closes #1773, #1838 (closed), #1846 (closed), #1843 (closed)

Risks

• No changes in wall-function output.
• No changes to user input.
  • New optional keyword into the yPlus function object: useWallFunction.
• Changes in the yPlus function object when the above nut wall functions are being used.

Tests

• Compilation: linux64ClangDPInt32Opt, linux64GccDPInt32Opt, linux64GccSPDPInt64Debug
• Alltest: No change
• simpleFoam & rhoSimpleFoam
• Verification: planeChannel

Verification 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}
• kOmegaSST & simpleFoam

Fields of interest:

• mag(wallShearStress) function object correctly returns ~ 1 for all test cases.
• yPlus function object (min) results for lowerWall rounded up to 2 decimals can be seen below:

y1+ = 0.05:

y1+ = 0.5:

y1+ = 1:

y1+ = 5:

y1+ = 10:

y1+ = 20:

y1+ = 30:

y1+ = 50:

y1+ = 100: