Restrict isOnWall()/isOnWallAtPos() in RANS to wall specific boundaries
Feature request A different format for the isOnWall function (and variations) used in the Rans Models
What does this feature / why does DuMux need it: At the moment the user can set the isOnWall function to any domain boundary face, regardless of the boundary conditions set there. This function should not be user defined, but be defined by the locations where wall boundary conditions have been specified.
Which issue does this feature fix (if any) This is related to !2224 (merged), !2289 (merged), and #941 (closed), but addresses a general issue with the Rans models