Your search terms would be 'wheel spats' and 'air curtain'.
The shear forces in the underbody are more straightforward than what's happening in the wheelwells. Try this:
Numerical simulation of the flow around the wheel within wheelhouse - Sasan_Sarmast_Jan2010.pdf
See also:
A_New_Aerodynamic_Approach_to_advanced_automobile_ shapes.pdf
On page seven Dr. A. Morelli describes a Fiat with centrifugal fans built into the wheels to suck air out of the wheelwells and eject it through slots in the underbody to separate the external turbulence and complete his 'fluid tail'.