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Influence of moving-belt dimensions on vehicle aerodynamic forces
Published April 14, 1997 by Royal Aeronautical Society in United Kingdom
This paper describes an investigation of the validity of using a short and narrow moving-belt as a means of facilitating the simulation of the road surface in a full-scale automotive wind tunnel. The project was jointly funded by Rover Group Ltd. and by MIRA.
Three 1:4-scale model vehicles were tested in the MIRA Model Wind Tunnel with moving-belt widths ranging from 250 percent down to 60 percent of the model width. The moving-belt length downstream of the models was then reduced from approximately one model length down to zero.
The models represented a passenger car, a 4 x 4 vehicle, and an F.1 racing car. Configuration changes were effected by varying the rear upper body shape, the underbody roughness and profile, the engine cooling airflow and the ride heights. Measurements were made of the drag and lift forces acting on the body of each model, and the drag of the wheels was measured separately.
Broadly, the results showed that both narrowing and shortening of the belt gave reductions in the model drag forces and increases in their lift forces (or reductions in down force where the lift was negative). The magnitude of these changes in forces was significant, especially in the case of the maximum reduction in belt size, and there was a degree of model configuration dependence.
It is therefore concluded that reducing the width of a moving-belt to allow it to run between the wheels of a car and shortening its length to fit within a typical balance turntable would significantly detract from the simulation of road conditions obtained with a "full-size"" moving belt.