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Influence of Geometry of Rear part on the Aerodynamic Drag and Wake Structure of a Vehicle
Technical Paper
871236
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English
Abstract
The substantial part of the drag of an automobile is the pressure drag. Therefore, the car must be designed as it produces minimum pressure drag. The present paper describes effects of geometrical configuration of the rear part of a car on the aerodynamic drag. Experiments were made on 1/5 scale models of fastback and notchback design.
For the fastback car the drag depends heavily on the angle of a rear window. At a certain critical angle the drag shows a sharp peak. This peak drag can be reduced drastically by the tapering of plan form of the rear geometry. For the notch-back design some combination of the angle of rear window and height of trunk deck shows similar maximum in the drag. Methods of avoiding the large drag were also found.
Our experiment was extended to the measurement of structure of wake by hot wire anemometers and total pressure tubes. The correlation between the wake structure and drag was clarified by the consideration of vorticity and circulation.
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Authors
Citation
Nouzawa, T., Hiasa, K., Yoshimoto, M., and Haruna, S., "Influence of Geometry of Rear part on the Aerodynamic Drag and Wake Structure of a Vehicle," SAE Technical Paper 871236, 1987.Also In
References
- Ahmed S.R. Ramm G. Faltin G. “Some Salient Features of the Time-Averaged Ground Vehicle Wake” SAE 840300 1984
- Bearman P.W. “Some Observations on Road Vehicle Wakes” SAE 840301 1984
- Hackett J.E. Sugavanam A. “Evaluation of a Complete Wake Integral for the Drag of a Car-Like Shape” SAE 840577 1984
- Cogotti A. “Car-Wake imaging Using a Seven-Hole Probe” SAE 860214 1986
- Nouzawa T. Hiasa K. Yoshimoto M. “Research of the Aerodynamic Characteristics through Wake Survey of Bluff Body -Second Report-” Mazda Technical Review 98 105 5 1937
- Nouzawa T. et al. “Current Techniques of Flow Visualization for Automobile Development” Flow Visualization 6 23 1986