James, M., Watkins, S., and Watts, M., "The Effect of Upstream Turbulence on an Exposed Wheel Wake," SAE Technical Paper 2014-01-0616, 2014, doi:10.4271/2014-01-0616.
As open-wheeled racing cars frequently race in close proximity, a limiting factor on the ability to overtake is the aerodynamic performance of the vehicle while operating in a leading car's wake. Whilst various studies have examined the effectiveness of wings operating in turbulent flow, there has been limited research undertaken on the aerodynamic effect of such conditions on wheels.This study describes the influence of upstream turbulence on the wake flow features of an isolated wheel, since the flow field of a wheel will generally be turbulent (due to the wakes of upstream cars and/or bodywork). Pressure distributions and velocity vector plots are examined, which were obtained using a four-hole pressure-sensitive Cobra probe on a traverse 2.5 diameters downstream of the wheel axle line, in smooth and turbulent flow.This analysis also compares the effect of upstream turbulence on the wake for the rotating and stationary wheel; as well as investigating the sensitivity of the wake to the wheel-to-road gap in smooth and turbulent flow.The study found that, at 2.5 diameters downstream, the overall wake width of the stationary wheel decreased with increased levels of turbulence, it also showed that the effect on the wake of increasing the wheel-to-road gap was independent of the level of turbulence in the flow. Both rotating and stationary wheel wake maps also displayed a higher minimum pressure with nominally turbulent flow, than those displayed by the corresponding wake maps with nominally smooth flow, and a much more gradual transition to free-stream pressure.