So far most researcWheels are a source of drag
-40% of the total drag on a Formula 1 car

Wheels have an influence on the aerodynamics of the car as a whole
-front and rear wings, underbody and diffuser

Wheels are a source of noise
-above 40 MPH wheels are the dominant source of road vehicle noise

Upper Near Wake
Stationary: Entrained main flow promotes a central attached flow down the rear face
Rotating: Arch shaped separation vortex cuts off flow down the rear face

Lower Separation
Presence of ground boundary layer causes a wider separation around the stationary wheel

Lower Near Wake
Stationary: Counterrotating longitudinal ground vortices formed from rolling up of flow down the rear face of the wheel
Rotating: Weaker longitudinal ground vortices formed from recirculation in lower separation