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Wind tunnel tests were carried out with a full-scale passenger car over a moving belt. The suspension system of the vehicle was redesigned in such a way that drag and lift forces could be measured whilst the wheels were rolling on the moving ground. The measurements were carried out with an internal balance installed inside the vehicle. Additionally, total-pressure-deficit contour plots were reduced from wake-rake measurements behind the front and rear wheels in order to identify the origin of different bound vortices generated at the wheels. It was found from these tests that rolling wheels have a large aerodynamic influence on passenger cars. They decrease the drag and increase the lift forces in comparison to fixed wheels. This has been established in an absolute and a relative sense by investigating different vehicle configurations.

This paper provides a method that corrects errors induced by the empty-tunnel pressure distribution in the aerodynamic forces and moments measured on an automobile in a wind tunnel. The errors are a result of wake distortion caused by the gradient in pressure over the wake. The method is applicable to open-jet and closed-wall wind tunnels. However, the primary focus is on the open tunnel because its short test-section length commonly results in this wake interference. The work is a continuation of a previous paper [4] that treated drag only at zero yaw angle. The current paper extends the correction to the remaining forces, moments and model surface pressures at all yaw angles. It is shown that the use of a second measurement in the wind tunnel, made with a perturbed pressure distribution, provides sufficient information for an accurate correction. The perturbation in pressure distribution can be achieved by extending flaps into the collector flow.

An acoustic comparison test of eleven European and two American full-scale automotive wind tunnels was carried out with a passenger car. The scope of investigation comprised in-flow and out-of-flow background noise measurements of the empty test sections as well as interior noise measurements inside the passenger compartment of a standard type Volkswagen Passat Variant CL. For this purpose seven different vehicle configurations were investigated in the various wind tunnels. The aim of this experimental investigation was to establish physical criteria in order to carry out a suitable acoustic comparison between wind tunnels with different types of test sections and to establish upper limits of wind tunnel background noise levels where acoustic measurements inside a passenger compartment are questionable.

The influence on aerodynamic drag of a non-uniform, streamwise pressure distribution over the wake of an automobile model in both open-jet and closed-jet wind tunnels is considered in this paper. It has long been an unsolved issue in the theory of open-jet interference and is usually not important in closed-wall wind tunnels unless the model is very long. A new, semi-empirical approach is presented that is based on the observation that the drag changes due to a pressure gradient over a wake correlate with the empty-test-section pressure-coefficient difference between the base of the vehicle and the position of wake closure. A method is demonstrated that is able to remove the effect of the pressure gradient and that is not buoyancy related. This method is applied to a range of simplified and detailed automobile shapes at model scale and at full scale in various wind tunnels, as well as to normal flat plates.

The results of comparative aerodynamic force measurements on a full-scale notchback-type vehicle, performed between 6 European companies operating full-scale automotive wind tunnels, were published in the SAE Paper 800140. Correlation tests with the same vehicle have been extended to 2 further European and 3 North American wind tunnels. First the geometry, the design and the flow data of the different wind tunnels is compared. The facilities compared include wind tunnels with open-test-sections, closed-test-sections and one tunnel with slotted side walls. The comparison of results, especially for drag coefficients, show that the correlation between the differently designed wind tunnels is reasonable. Problems of blockage correction are briefly discussed. The comparison tests furthermore revealed that careful design of the wheel pads and blockage corrections for lift seem to be very influential in achieving reasonable lift correlations. Six-component measurements show similar problems.

Two different techniques, ground plane suction and blowing, were used in order to decrease the displacement thickness of the floor boundary layer in wind tunnels upstream of full-scale vehicles. A detailed description of both systems is given and comparison tests in three different wind tunnels were carried out. The vehicles tested were full-size passenger cars and simplified-model cars of notch back, fast back and wagon back type, as well as sport cars and a racing car with different trim heights simulating different ground clearances.

Full-scale vehicle tests were made on a standard-type passenger car in a wind tunnel and on the road in order to evaluate different moving-ground simulation techniques for wind tunnels. The test was first executed over a moving belt, supporting the car with a rear sting and measuring the aerodynamic forces with an internal balance. The test was then repeated with the same support arrangement over a fixed test-section floor, and moving-ground simulation was attained with boundary layer control by tangential blowing. Besides force measurements, the surface pressure distribution underneath the vehicle and at the base were also measured. Furthermore, the velocity distribution between vehicle and ground floor was assessed by measuring the total-pressure distribution.