A Comparison Between On-Road and Wind Tunnel Surface Pressure Measurements on a Mid-Sized Hatchback

The aerodynamic development and evaluation of passenger vehicles is almost universally performed in the controlled, low turbulence environment of a wind tunnel or under similarly idealized conditions using CFD. This environment is substantially different from that which is experienced on-road due to the effects of atmospheric winds and the wake flows from other road vehicles. The scope of this work is to establish, with regard to surface pressures, if a low turbulence wind tunnel evaluation of passenger cars yields results which accurately reproduce on-road data or whether a more complete simulation of the real world is required. The test vehicle was a Rover 214, a typical European mid-sized hatchback. Data were obtained from both the MIRA full-scale wind tunnel and on the road using the same vehicle and instrumentation. The on-road data were gathered under various atmospheric wind conditions. Time averaged surface pressures for the centerline, side glass and backlight are presented together with the standard deviations associated with those side glass pressures. Also presented are the characteristics of the turbulence experienced on the road. The results demonstrate differences between wind tunnel and road data that confirm the need for extended research over a broader range of vehicle geometries and for the need for more detailed analysis of the flow physics.