The Aerodynamic Characteristics of a Fully Deformable Formula One Wind Tunnel Tyre

Competitive aerodynamic performance of a Formula One car relies upon total understanding of the downstream wake of exposed rotating wheels. Sensitivities to the downstream vortices and low stagnation-pressure regions lead to subtle design decisions in bargeboards, side-pods and the leading edge of the highly sensitive floor region. A significant proportion of an F1 aerodynamicist's time is spent dealing with front wheel wake structures and indeed much of the front wing is developed to provide pressure gradients and vortex structures to control this wake. Wind tunnel testing of scaled deformable tyres has become a common occurrence in F1 in recent years although there is a significant lack of available literature, academic or otherwise. Due to high vertical loads experienced by a grand prix car and the relatively high levels of camber used for mechanical advantage, the use of a rigid tyre is no longer considered suitable for the accurate simulation of an F1 wheel wake. This investigation has studied in detail the aerodynamic consequences born from sidewall bulge and contact patch parameters through the use of an innovative rotating sidewall scanning technique, static contact patch measurements, five-hole pressure-probe wake measurements, Particle Image Velocimetry (PIV) and load-cell drag measurements. A table of three-dimensional coordinates for the maximum and minimum deformation levels has been included in this paper to enable further CFD studies to be undertaken. For longevity of tyre and moving ground plane, deformation levels are often fairly conservative in industrial and race team applications. The work presented here includes a full range of on-track axle heights, which far exceed those usually tested in the aforementioned settings and the aerodynamic consequences of under-deforming have been identified. It has been concluded that insufficient deformation of the tyre sidewalls leads to a significant overestimate in the width of the wake as well as the aerodynamic loads associated with it. As a result of this study, the most sensitive parameters of a deformable tyre relating to aerodynamic testing have been identified and summarised. For development of an F1 car, a compromise in tyre pressure is considered less detrimental to the downstream wake compared to providing insufficient deformation with an incorrect axle height.