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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.

Modern vehicles require a low aerodynamic drag to minimize fuel consumption. A not negligible share of the overall CD-value of a vehicle is produced by the engine compartment air flow. Therefore this share has also to be optimized. Furthermore, customer wishes for higher powered engines as well as for more safety and comfort result in more tightly packed engine compartments. Even the reduction of pass-by-noise required by legal reasons is often achieved with the help of underbody covers which in turn affect the engine compartment flow. All these items may lead to rising underhood temperatures. To reduce the development time of new vehicles, numerical simulations of engine compartment air flow are more and more used to predict high temperature fields and to show ways to develop suitable remedies in the concept phase of the vehicle development. The experimental basis for such codes is provided by aerodynamic investigations in a wind tunnel.

Aeroacoustics is playing an increasing role in the development of new passenger cars. However, most existing wind tunnels, with few recent exceptions, have been designed and built with little or no attention to their aeroacoustic aspects. Building new wind tunnels with excellent low noise levels is technically feasible today, however it is not often justifiable from an economic standpoint. In the case of the Pininfarina wind tunnel, built in 1972 without any specific noise target, a decision was taken in 1984 to progressively upgrade the facility and the acoustic measuring techniques. A target of reaching a background noise level low enough to allow satisfactory acoustic development work on new cars, with the contemporary use of more modern measuring techniques, was established. This decision implicitly assumed that, to do this development work, it is not necessary to reach the very low noise levels of a pure acoustic wind tunnel.

The paper summarizes various flow-field survey techniques which have been developed at Pininfarina in recent years to analyse the flow field around cars in the wind tunnel. Some of these techniques are now fully integrated into wind tunnel everyday work. Among them, the “14-hole probe” technique has been recently upgraded by the development of two new “micro-drag” and “vorticity” maps. The paper describes the most recent advances in these techniques and, mainly, the strategy employed in the Pininfarina wind tunnel to maximize the usefulness of the information obtained about a car flow-field with a minimum of wind tunnel run-time. The core of this strategy is the choice of a carefully chosen set of planar surveys carried out around the car in the most critical areas, so that a complete overview of the whole car flow-field can be achieved.

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.