The unsteady environment road vehicles are exposed to is subject of many investigations that are currently made. Yet, the approaching flow is only one aspect of unsteady forces acting on the vehicle. Unsteady wake structures also lead to time-varying surface pressures and consequently fluctuating forces even in steady and low turbulent flows. However, little is known about the influence of realistic flow conditions, i.e. as found on road, on the unsteady surface pressures and wake structures of a vehicle.
Therefore, to derive a deeper understanding of the unsteady aerodynamic properties of a vehicle this paper presents results of measurements conducted on a vehicle body both in smooth and turbulent flow conditions in the IVK model scale wind tunnel. Unsteady surface pressure measurements in the area where separation occurs and the base of the vehicle were made together with time accurate total pressure measurements in the wake. The analysis of periodic surface pressure fluctuations and flow structures reveals remarkable changes in time averaged and instantaneous properties of the flow field when the turbulence intensity is brought to levels typical for on road conditions.
These findings give insight into the interaction between realistic turbulence levels and changes in the flow around the vehicle body. From this the impact on unsteady forces is derived.
