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As part of the general program for comparing leading European automotive wind tunnels, three reference cars derived by Volkswagen (VW), Pininfarina (PF) and FIAT Research Center (CRT) from production models, were tested in different configurations. This report contains the result of tests carried out on a CRF reference car in CRF, VW, DB and PF wind tunnels as well as on the road. The wind tunnel tests of the car in 7 different configurations show a fairly good agreement particularly for the drag coefficients measured in the various tunnels. Road tests were carried out with the car in three configurations at constant speed (measuring front and rear axle lift, body pressure and visualising the wake) and in coast-down (measuring aerodynamic resistance). The results obtained proved that road driving conditions with no side wind or turbulence are correctly simulated in wind tunnel tests.

Comparative aerodynamic force measurements on a full scale notchback type vehicle have been performed between six European companies operating prominent full scale automotive wind tunnel facilities. The results obtained with 8 different vehicle configurations show a remarkably good correlation between the drag coefficients measured in the various wind tunnels. Pressure distributions also show an acceptable agreement. The comparison of front axle lift measurements revealed differences between the various wind tunnels; these differences are partly explainable. Six component measurements also show a satisfactory correlation between the various wind tunnels except where lift does contribute to the forces or moments. Suggestions to extend these correlation tests are presented.

A correlation test program between four European full-scale automotive wind tunnels has been performed on a passenger car modified in five different rear-end configurations which cover most of the present passenger cars. The aim of this program was mainly to evaluate to what extent the aerodynamic drag coefficients, measured in these four different wind tunnels, are reliable and therefore can be used for technical or legislative purposes. The correlation program was extended also to the other force coefficients, that is, lift and side forces, and to the pressure distributions. Tests were carried out at different speeds from 90 to 150 Km/h and at different yaw angles β from − 50° to + 50°. The comparison shows a generally good agreement between the results of these four tunnels, the differences for tests at β = 0° being, in terms of the standard deviations, in the order of ± 2% as regards the drag coefficient, ± 0.025 and ± 0.011 as regards the front and rear lifts.

During the past few years substantial advances have been made in reducing the drag of automobiles. Future improvements are becoming increasingly difficult to achieve; for this reason more-advanced flow investigation methods are required. This paper shows some results of flow analysis performed using two methods. The first is experimental and is based on car-wake flow surveying; the second is computational and is based on inviscid flow calculations simply corrected for viscous effects. The two methods may be usefully combined.

Automotive aerodynamic resistance is going lower and lower. New cars have a Cx near 0.30 and the trend is to reduce the drag even further. At this level the contributions of the car underside, wheel cavities and engine-cooling-system play an important role in the total drag. This paper shows relevant results from wind tunnel tests on a 1/1 scale model equipped with internal balances which allow measurement of the individual drag contributions from the car underside and upper body. Total drag was measured with the wind tunnel balance. The resistance of the engine-cooling-system was directly measured, and compared with the value obtained from the difference in the car total drag when tested with and without the radiator-intake sealed. Test results also show effect and interactions due to configuration changes.

Endurance cars regulations require an heavy aerodynamic research aimed to minimize car drag and to generate, in the meantime, high negative lift characteristics, both to reduce fuel consumption and to increase the car handling and cornering performance. This paper shows the work done to define new rear wing sections; it is essentially based on the use of computational aerodynamic programs, employed by aeronautical industries, and of corresponding wind tunnel tests. The work program was the following : a) Computational aerodynamic program validation by means od wind tunnel tests on an existing rear wing, aimed to compare theoretical and experimental results b) Use of computational aerodynamic program to define new wing contours with and without slotted flaps c) Wind tunnel tests on real scale isolated wings with new profiles defined by computational aerodynamic program d) Real car and 1/5 scale model wind tunnel tests to minimize the interferences between rear wing and car body.

Measurements are presented showing the influence of the trunk length of a road vehicle on drag coefficient. The experiments were made in the “Politecnico di Torino” wind tunnel on a 1/5 scale model. Data from balance measurements, body-surface pressure and wake flow surveys are reported. A method is shown for correlating to the aerodynamic drag data from wake survey.