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 2m₂ 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 visualization 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.
