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The turbulence environment in the real world is known to be significantly different to that found in a typical automotive wind tunnel. Various studies have shown that raising the level of freestream turbulence has an effect on the forces on generic bluff bodies and real vehicles. Previous work at Loughborough has shown a significant effect of raised freestream turbulence on edge radius optimisation using measurements of forces and moments, and in this paper the underlying changes in the flowfield are investigated using PIV. Results are presented of the flowfield around the leading edge radius of the generic bluff body used in the previous work. The effect of changing the Reynolds number is investigated in the clean tunnel (0.2% turbulence), and it is found that, when the radius is small, there is a significant separation that persists up to a high speed, and then abruptly collapses.

It has been recognised that the ideal flow conditions that exist in the modern automotive wind tunnel do not accurately simulate the environment experienced by vehicles on the road. This paper investigates the effect of varying one flow parameter, freestream turbulence, and a single shape parameter, leading edge radius, on aerodynamic drag. The tests were carried out at model scale in the Loughborough University Wind Tunnel, using a very simple 2-box shape, and in the MIRA Full Scale Wind Tunnel using the MIRA squareback Reference Car. Turbulence intensities up to 5% were generated by grids and had a strong effect on transcritical Reynolds number and Reynolds sensitivity at both model scale and full scale. There was a good correlation between the results in both tunnels.