Search Results

Starting from September 2006, a new Moving Ground System is in operation in the Pininfarina wind tunnel. This system has replaced the old one, in service since 1995, which was the first in the world with a narrow belt integrated into the balance/turntable. The new Moving Ground System has a number of improvements, namely: An increased top speed, up to 250 Km/h A much longer and slightly wider central belt, e.g. it is 6.7 m long and 1.1 m wide Two additional belts at the sides A number of innovative features that make this system well suited for testing racing cars. In particular, this system has two additional belts at the sides of the central belt to cover the part of the ground that is under the car front end, for a width of 2.5 m and a length of 1.5 m. This feature, patented by Pininfarina, greatly improves the simulation of the flow under the front wing of a Formula 1 car or under the front end of a racing car. Details are shown in the paper.

Starting from September 2006, a new Moving Ground System is in operation in the Pininfarina wind tunnel. This system has replaced the old one, in service since 1995, which was the first in the world with a narrow belt integrated into the balance/turntable. The new Moving Ground System has a number of improvements, namely: - An increased top speed, up to 250 Km/h. - A much longer and slightly wider central belt, e.g. it is 6.7 m long and 1.1 m wide. - Two additional belts at the sides. - A number of innovative features that make this system well suited for testing racing cars. In particular, this system has two additional belts at the sides of the central belt to cover the part of the ground that is under the car front end, for a width of 2.5 m and a length of 1.5 m. This feature, patented by Pininfarina, greatly improves the simulation of the flow under the front wing of a Formula 1 car or under the front end of a racing car. Details are shown in the paper.

Aerodynamic drag of a modern car is generated mainly by underbody flows. A better understanding of these flows and of their interactions with the car underbody, may contribute to the future improvement of the car drag characteristics. This paper reports the results of a parametric study carried out in the Pininfarina wind tunnel, on a full scale simplified car model, by using the Ground Effect Simulation System built in 1995. The main aim of this study was to investigate the effect on the aerodynamic coefficients produced by important geometric changes which affect the flows under the car, in proximity of the ground, and are often difficult or impossible to be modified when tests are made on real cars. The model chosen for this research program is that defined by the SAE “Open Jet Interference Committee” as a reference model to be used for investigating wind tunnel interference and for comparison between wind tunnels. In particular it has no wheels.

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.

The paper refers to a research program which is presently in progress at Pininfarina. It deals with a new ground effect simulation system for full-scale car testing in an automotive wind tunnel. This research program is carried out in the framework of the “Progetto Finalizzato Trasporti 2” of the Italian C.N.R. The first part of the paper makes an analysis of: The various ground effect simulation systems already existing in the world. The results which can be achieved using these systems. Their main limitations and drawbacks and some considerations about the possibility of using these systems for routine aerodynamic development work on full-scale vehicles. The second part of the paper describes the new Ground Effect Simulation System (GESS) which is presently in operation in the wind tunnel of the Pininfarina Aerodynamic and Aeroacoustic Research Center. Its layout is quite different from the ground effect simulation systems existing in other full-scale automotive wind tunnels.

The flow-field mapping technique previously developed in the Pininfarina wind tunnel has further evolved during 1986. The former technique (1985), based on the use of a “seven-hole” probe, had two main limitations: poor sensitivity at low speed (<8 m/sec.) incapability of measuring at flow angles greater than +− 70° Both these conditions often occur inside the near-wakes of passenger-car models. Therefore, wake maps (velocities and pressures) made in the past were largely incomplete in their inner parts. The new probe has a double “seven-hole” pattern and its performance exceeds that of two “seven-hole” probes used separately. It was developed during the fourth year of a research program aimed at providing new experimental information on reverse flows in automobile wakes, for use in developing improved computational fluid dynamic (CFD) techniques for automobiles. Reverse flows inside the near-wake of three full-scale squareback car models were 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”.