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. The agreement seems to be satisfactory also for force measurements in side wind conditions and for pressure measurements.