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The effect of the upstream wake of a Formula 1 car on a following vehicle has been investigated using experimental and computational methods. Multiple vehicle studies in conventional length wind tunnels pose challenges in achieving a realistic vehicle separation and the use of a short axial length wake generator provides an advantage here. Aerodynamic downforce and drag were seen to reduce, with greater force reductions experienced at shorter axial spacings. With lateral offsets, downforce recovers at a greater rate than drag, returning to the level for a vehicle in isolation for offsets greater than half a car width. The effect of the wake was investigated in CFD using multiple vehicle simulations and non-uniform inlet boundary conditions to recreate the wake. Results closely matched those for a full two-vehicle simulation provided the inlet condition included unsteady components of the onset wake.

Detailed flow-field measurements in the wake of a 40 percent full-scale exposed wheel have been obtained using particle image velocimetry (PIV). Additional data have been acquired in the form of surface static pressure measurements acquired using the Durham University radio telemetry system. The results presented in this paper compare and contrast, both quantitatively and qualitatively, the physical differences that exist with respect to the flow structures of rotating and non-rotating wheels. Some of the ‘special’ features of the flow-field postulated by Fackrell, such as the ‘jetting’ phenomenon, have been revisited, examined and revised based on the surface static pressure and PIV data presented in this paper. The experimental observation of a flow mechanism is presented in terms of the rear jetting after the line of contact, and the effects of this have been considered and analyzed.

A radio telemetry system has been designed and developed at Durham University that enables surface pressure data to be transmitted from a rotating racing wheel to a host PC, where data post-processing is carried out. A multi-element wheel rim has been designed to allow the telemetry system to be located inside a pneumatic tire. Surface pressure distributions around the centerline of the wheel show good agreement with previous research. A flow field investigation has also been conducted, downstream of the wheel, for both stationary and rotating wheel cases. The results presented highlight some of the key features of the flow field and give confidence in the telemetry system.

Transient wake surveys have been conducted on a generic three dimensional vehicle shape. The flow conditions were those generated by the unique crosswind facility at Durham University, which imitates a vehicle passing through a sharp-edged, finite length cross-wind gust. Each survey consisted of some 7000 cross-wind gusts, with each point in the wake being phase-averaged over 20 gusts. The surveys clearly show the development of the wake structure from the familiar axial flow conditions, through the transient to a nominally steady yawed flow. Although both the structure and total pressure loss that develop in the wake flow are comparable to those found for quasi-steady flow conditions, the developing flow reveals characteristics that are not found in the quasi-steady measurements. New data are also presented with regard to the character of the gust that develops in this wind tunnel and their impact upon the reported wake measurements is discussed.