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The Effect of Base Bleed and Rear Cavities on the Drag of an SUV
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 12, 2010 by SAE International in United States
Annotation ability available
Two methods of passive flow control were investigated to determine their effectiveness in reducing aerodynamic drag on large Sports Utility Vehicles (SUVs). Passive means of flow control were selected since all active methods require the input of additional energy (e.g., pressurized fluids or electrical energy). The selected methods were base bleed and the use of a rear cavity, and various combinations of these were experimentally tested in full-scale wind tunnels with and without a moving belt/rotating wheel assembly. Aerodynamic drag reduction was accomplished by restructuring the low-pressure wake directly behind the vehicle.
External cavity depths ranging from d/h=0.17 to 0.83 were used, while body cavity depths ranged from d/h=0 to 0.83, where the depth of the cavity d is non-dimensionalized by the height h of the base area. External cavities always resulted in an increase in the drag coefficient, while for body cavities the reduction in drag improved with increasing cavity depth. A maximum drag reduction of -3.3% was achieved.
The base bleed coefficient was varied from Cq=(3-21) x 10-⁴, and various bleed outlet locations in the base area were considered. Bleeding air around the periphery of the base area was found to be the most effective implementation, and depending on the outlet location the drag reduction ranged from -0.3% to -1.1%.
CitationIrving Brown, Y., Windsor, S., and Gaylard, A., "The Effect of Base Bleed and Rear Cavities on the Drag of an SUV," SAE Technical Paper 2010-01-0512, 2010, https://doi.org/10.4271/2010-01-0512.
- Fukuda, H. Yanagimoto, K. China, H. Nakagawa, K. “Improvement of vehicle aerodynamics by wake control,” JSAE Review 16 151 155 1995
- Gaylard, A.P. “The Appropriate Use of CFD in the Automotive Design Process,” SAE Technical Paper 2009-01-1162 2009
- Tanner, M. “Reduction of Base Drag,” Prog. Aerospace Sci. 16 4 369 384 1975
- Mair, W.A. “Drag-Reducing Techniques for Axi-Symmetric Bluff Bodies,” AIChE Symposium Series 161 187 1978
- Oertel, H., Jr. “Wakes Behind Blunt Bodies,” Annual Review of Fluid Mechanics 22 539 564 1990
- Viswanath, P.R. “Flow Management Techniques for Base and Afterbody Drag Reduction,” Prog. Aerospace Sci. 32 79 129 1996
- Morel, T. “Effect of base cavities on the aerodynamic drag of an axisymmetric cylinder,” Aeronautical Quarterly 30 400 412 1979
- Goodyer, M.J. “Some experimental investigations into the drag effects of modifications to the blunt base of a body of revolution,” Institute of Sound and Vibration, University of Southampton 1966
- Nash, J.F. Quincey, V.G. Callinan, J. “Experiments on two-dimensional base flow at subsonic and transonic speeds,” Aeronautical Research Council R & M 3427 1966
- Khalighi, B. Zhang, S. Koromilas, C. Balkanyi, S.R. Bernal, L.P. Iaccarino, G. Moin, P. “Experimental and Computational Study of Unsteady Wake Flow Behind a Bluff Body with a Drag Reduction Device,” SAE Technical Paper 2001-01-1042 2001
- Geropp, D. Odenthal, H.-J. “Drag reduction of motor vehicles by active flow control using the Coanda effect,” Experiments in Fluids 28 74 85 2000
- Howell, J. Sheppard, A. Blakemore, A. “Aerodynamic Drag Reduction for a Simple Bluff Body Using Base Bleed,” SAE Technical Paper 2003-01-0995 2003
- Englar, R.J. “Drag Reduction, Safety Enhancement, and Performance Improvement for Heavy Vehicles and SUVs Using Advanced Pneumatic Aerodynamic Technology,” SAE Technical Paper 2003-01-3378 2003
- Wood, C.J. “Visualization of an incompressible wake with base bleed,” J. Fluid Mech. 29 2 259 272 1967
- Leal, L.G. Acrivos, A. “The effect of base bleed on the steady separated flow past bluff bodies,” J. Fluid Mech. 39 4 735 752 1969
- Sykes, D.M. “The Effect of Low Flow Rate Gas Ejection and Ground Proximity on After Body Pressure Distribution,” 1st Symposium on Road Vehicle Aerodynamics City University London, United Kingdom November 1969
- Kohri, I. Kataoka, T. “Reduction of Aerodynamic Drag with Base Bleed System,” Journal of JSAE 45 4 78 83 1991
- Zhdanov, V.L. “Effect of Jet Bleed Out of the Base of a Model on the Base Pressure and Frequency Characteristics of Wake Flow,” Journal of Engineering Physics and Thermophysics 71 4 627 632 1998
- Sterneus, J. Bannister, M. Volvo Car Corporation Test Report No. 288638 2007