This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
On-Road Aerodynamic Drag Measurements Compared with Wind Tunnel Data
Annotation ability available
Sector:
Language:
English
Abstract
Ever since aerodynamics became an essential element of the automobile design process, the principal development tool for the vehicle aerodynamicist has been the full-scale wind tunnel. In the absence of a reliable alternative, it is expected that this will continue for many years.
As a true simulation of the conditions on the road the conventional full-scale wind tunnel has limitations. The ground is fixed relative to the vehicle allowing an unrepresentative boundary layer to develop, the wheels of the test vehicle do not rotate and there is some uncertainty over the influences imposed by the tunnel walls. In addition, the aerodynamic data obtained from different wind tunnels shows a degree of scatter and even configuration changes do not necessarily produce consistent effects.
With particular regard for aerodynamic drag, the aerodynamicist should ensure that gains obtained in the wind tunnel generate real benefits on the road. This paper describes work undertaken to enhance the understanding of differences between road and wind tunnel derived data. To assist this process, an advanced coastdown technique has been employed to determine aerodynamic drag on the road. In contrast with previous investigations, the principal vehicle tested was systematically reconfigured to provide a range of drag and lift characteristics. Saloon and fastback vehicle shapes have been tested with a range of front and rear spoilers. In addition, the influence of underfloor smoothing and the effects of wheel design and tyre size were studied.
Comparison of track results with data derived from one wind tunnel shows that the wind tunnel under-predicts drag and that differences are configuration dependent. In certain cases a relationship with lift is established.
Recommended Content
Topic
Citation
Le Good, G., Howell, J., Passmore, M., and Garry, K., "On-Road Aerodynamic Drag Measurements Compared with Wind Tunnel Data," SAE Technical Paper 950627, 1995, https://doi.org/10.4271/950627.Also In
References
- COGOTTI A. et al Comparison Tests Between Some Full-Scale European Automotive Wind Tunnels - Pininfarina Reference Car SAE 800139 1980
- BUCHHEIM R. et al Comparison Tests Between Major European Wind Tunnels SAE 800140 1980
- COSTELLI A. et al FIAT Research Centre Reference Car Correlation Tests Between Four Full Scale European Wind Tunnels and Road SAE 810187 1981
- CARR G.W. Correlation of Aerodynamic Force Measurements in MIRA and Other Automotive Wind Tunnels SAE 820374 1982
- HOWELL J.P. HAYNES T.L. Wind Tunnel Correlation Rover Internal Report October 1991
- CARR G.W. ROSE M.J. Correlation Of Full-Scale Wind Tunnel Measurements Of Aerodynamic Drag MIRA Report No. 1958/10
- MORELLI A. et al Automobile Aerodynamic Drag on the Road Compared With Wind Tunnel Tests SAE 810186 1981
- EAKER G.W. Wind Tunnel-to-Road Aerodynamic Drag Correlation SAE 880250 1988
- ROUSSILON G. Contribution To An Accurate Measurement Of Aerodynamic Drag From Coastdown Tests And Determination Of Actual Rolling Resistance Proceedings of 4th Colloquium on Industrial Aerodynamics Aachen 18-20 June 1980
- MERCKER E. KNAPE H.W. Ground Simulation With Moving Belt And Tangential Blowing For Full-Scale Automotive Testing In A Wind Tunnel SAE 890367 1989
- LARSSON L. et al A Study Of Ground Simulation Correlation Between Wind-Tunnel And Water Basin Testing Of A Full-Scale Car SAE 890368 1989
- PASSMORE M.A. JENKINS E.G. A Comparison of the Coastdown and Steady State Torque Methods of Estimating Vehicle Drag Forces SAE 880475 1988
- PASSMORE M.A. The Measurement And Analysis Of Road Vehicle Drag Forces Loughborough University of Technology 1990
- PASSMORE M.A. LE GOOD G.M. A Detailed Drag Study Using The Coastdown Method SAE 94 420 1994
- SCHURIG D.J. et al Transient Speed and Temperature Effects on the Rolling Loss of Passenger Car Tires SAE 850463 1985
- HOWELL J.P. The Influence Of A Vehicle Underbody On Aerodynamic Drag IMechE Autotech Congress 1991
- MULLENBACH P. DEUTENBACH K-R. Influence Of Boundary Layer Control Systems To The Flow Fields Around Passenger Cars Proceedings of 8th Colloquium on Industrial Aerodynamics Aachen 4-7 September 1989
- MERCKER E. A Blockage Correction For Automotive Testing In A Closed Wind Tunnel Journal of Wind Engineering and Industrial Aerodynamics 22 1985 149 167
- CARR G. W. The Aerodynamics of Basic Shapes for Road Vehicles, Part 3, Streamlined Bodies MIRA Report No. 1970/4