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In 1995, in order to bring the wind tunnel simulation as close as possible to the road condition, Pininfarina integrated the “rolling road” with the balance system and provided a means to rotate the car wheels. That was certainly an important first step to improve the airflow simulation of a vehicle moving on the road. However, to reproduce real on-road flow conditions in the wind tunnel, it is necessary to do a second equally important step. That is, it is necessary to be able to reproduce turbulent flow conditions similar to what a vehicle usually experiences on the road. In fact, it is known from previous works that for most of the time, a road vehicle is moving in the presence of turbulent flows, generated either by some natural low-speed wind or by other vehicles moving upstream. These flow conditions are very different from the almost perfect low-turbulence flow that is typical of modern automotive wind tunnels.

Particle Image Velocimetry (PIV) is a recent measuring technique, which has been used up to now mainly by University Laboratories in small-scale wind tunnels and by Aeronautical Research Centers in small and large facilities. Its use in full-scale automotive testing is not common. It is not so easy, often rather difficult, due to a number of problems, sometimes of practical nature, sometime caused by technology limitations. This paper reports the results of some tests, carried out by CIRA (Centro Italiano Ricerche Aerospaziali) in the Pininfarina wind tunnel on a full-scale car, in the frame of the European Thematic Network “PIVNET”. A description of the test set up, of the instrumentation used for these tests, as well as an analysis of the advantages provided by this technique and of its present limitations, are reported. During the tests, in order to outline the potential of this measuring technique, some specific areas of the car flow field, have been investigated.

Aerodynamics of modern cars is usually investigated in condition of very low turbulence flow and zero yaw. Furthermore, the majority of the tests are often carried out in wind tunnels with fixed ground and static wheels. The effects of a more realistic flow simulation on the car underbody produced by the ground motion and the wheel rotation have been reported in the SAE paper 980031 presented at the 1998 Int’I SAE Congress. This parametric study was carried out in the Pininfarina wind tunnel, by using the Ground Effect Simulation System (“GESS”) built in 1995 and a full-scale simplified car model. This paper reports the follow up of this investigation. The same simplified car model and its underbody interchangeable underbody parts has been tested again, using the “GESS”.