Fix the naming of wss field in the output of fieldConvert module

Issue

When we compute the wall shear stress using WSS module in FieldConvert, it produces new fields but the naming for these shear stresses are misleading. Currently, the names of new fields are "WSS_x" and "WSS_y" which implies these shear stresses are in x and y directions. However, they are not. They are in streamwise and normal directions at each point on the wall. It is more convenient to have the name of these fields such that avoid any confusions.

Proposed solution

I just modified the name of the output files as follows:

• WSS_x ---> WSS_s
• WSS_y ---> WSS_n

Implementation

It is implemented in library/FieldUtils/ProcessModules/ProcessWSS.cpp file

Tests

Since only two strings (the names) are changed, didn't provide any test for it. The WSS module already has tests and the name of variables in those tests are updated

Notes

Few lines are added for clarifications to the user guide as well

Checklist

• Functions and classes, or changes to them, are documented.
• [X ] User guide/documentation is updated.
• [X ] Changelog is updated.
• [X ] Suitable tests added for new functionality.
• Newly added files are correctly formatted.
• License added to any new files.
• [X ] No extraneous files have been added (e.g. compiler output or test data files).