The wall-bounded flow tends to separate at around the top of the wheel and forms a large area of low pressure behind the wheel. This is the basis of the drag on the wheel. This results in a pair of “jets” that travel around the contact patch. These “jets” then merge with the high speed freestream, laying the foundation for the counter-rotating vortex pair in the near wake.

The CVP is formed at around one diameter downstream of the wheel axle, due to the joint effort of the reversed “jets” behind the contact patch and the entrainment of the front separation flow. This CVP has relatively low velocity with high turbulence especially in ground proximity.

Usually in scientific research, the wheel is studied in isolation. However, in Formula racing, the effect of the front wing on the wheel wake is simply too great to ignore. To correctly condition the flow onto the wheel, the front wing must be included in both configurations.

The result of configuration one (without the flow deflector) is shown in Figure 2 with the fundamental flow structure such as the CVP preserved but its location shifted inboard by the suction effect created beneath and behind the front wing.

Figure 2: Velocity vectors at one diameter downstream of the wheel axle showing CVP, overlaid on velocity contour at the same location.