Aerodynamic Investigation on the Effect of Varying Through-Hub Flow on a Formula One Front Wheel Assembly

For open wheel race cars the front wheel flow and the interaction of its wake with downstream components is of significant importance. Considerable effort goes into the design of front wing end plates, barge boards and underfloor components in order to manage the front wheel flow. In this study a 50% scale Formula One front wheel assembly has been tested in the Durham University 2m(2) open jet wind tunnel to evaluate the effect of through-hub flow on its cooling drag and flow structures. Varying the amount of through- hub flow gave rise to a negative cooling drag trend whereby increasing the flow through the hub resulted in a decrease in drag. This observation has been explained both qualitatively and quantitatively by inlet spillage drag. Lower than optimum airflows through the brake scoop result in undesirable separation at the inside edge and hence, an increase in drag (reversing the cooling drag trend). The dominant processes at different flow rates have been assessed by applying several modifications to the scoop design in order to suppress or overcome the contributions to the drag change. This methodology has also shown a greater aerodynamic efficiency across the whole through- hub flow range for the case with rounded edges. A combination of PIV, pressure probe wake maps, CFD and surface flow visualisation techniques have been used to investigate the effect of through- hub flow on the overall wake of the wheel. The well documented counter rotating vortices or ground lobes are shown to be displaced toward the outboard side due to the outflow of the cooling flow causing a lower pressure. The size of these vortices also changes significantly with through- hub flow rate. The effect of outboard wheel fairings has been investigated in the context of through- hub flow. By positioning the exit orifice facing downward or rearward, the overall drag was significantly reduced and the structure of the wake was further altered toward the outboard side.