This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Experimental and Computational Study of Unsteady Wake Flow Behind a Bluff Body with a Drag Reduction Device
Technical Paper
2001-01-1042
ISSN: 0148-7191, e-ISSN: 2688-3627
Annotation ability available
Sector:
Event:
SAE 2001 World Congress
Language:
English
Abstract
Simple devices have been shown to be capable of tailoring the flow field around a vehicle and reducing aerodynamic drag. An experimental and computational investigation of a drag reduction device for bluff bodies in ground proximity has been conducted. The main goal of the research is to gain a better understanding of the drag reduction mechanisms in bluff-body square-back geometries. In principle, the device modifies the flow field behind the test model by disturbing the shear layer. As a consequence, the closure of the wake is altered and reductions in aerodynamic drag of more than 20 percent are observed. We report unsteady base pressure, hot-wire velocity fluctuations and Particle Image Velocimetry (PIV) measurements of the near wake of the two models (baseline and the modified models). In addition, the flows around the two configurations are simulated using the Reynolds Averaged Navier-Stokes (RANS) equations in conjunction with the V2F turbulence model. In order to capture the oscillating behavior of the wake the equations are solved in their unsteady form.
The mean pressure results show a significant increase in the base pressure with the drag reduction device. For the present geometries, the drag reduction device suppresses large-scale turbulent motions in the wake. The results show a reduction of the turbulence intensity as well as a rapid upward deflection of the underbody flow with the device in place. The effect of the drag reduction device on the length of the recirculation region in the near wake is small. Furthermore, the results confirm that the separated flow from the trailing edge of the model reattaches on the extended plate (add-on device) which is similar to that of a boat-tail effect. This boat-tail effect is documented by mean flow streamlines that show the dividing streamlines originating at the tip of the plates making the recirculation region narrower even though the main recirculation length does not change. Finally, both the measurements and simulations reveal that the instantaneous flow fields differ significantly from the averaged ones.
Recommended Content
Authors
Citation
Khalighi, B., Zhang, S., Koromilas, C., Balkanyi, S. et al., "Experimental and Computational Study of Unsteady Wake Flow Behind a Bluff Body with a Drag Reduction Device," SAE Technical Paper 2001-01-1042, 2001, https://doi.org/10.4271/2001-01-1042.Also In
SAE 2001 Transactions Journal of Passenger Cars - Mechanical Systems
Number: V110-6; Published: 2002-09-15
Number: V110-6; Published: 2002-09-15
References
- Mair, W.A. “Drag-Reducing Techniques for Axi-Symmetric Bluff Bodies,” Aerodynamic Drag Mechanisms of Bluff Bodies and Road Vehicles,” Plenum Press, New York 1978 161 187
- Lanse, W.R. Ross, J.C. Kaufman, A.E. “Aerodynamic Performance of a Drag Reduction Device on a Full-Scale Tractor/Trailer,” SAE Paper 912125 1991
- Bearman, P.W. “Investigation of the Flow Behind a Two-Dimensional Model with a Blunt Trailing Edge and Fitted with Splitter Plates” J. Fluid Mech. 21 241 255 1965
- Mansingh, V. Oosthuizen, P.H. “Effects of Splitter Plates on the Wake Flow Behind a Bluff Body” AIAA J. 28 778 783 1990
- Mason, W.T. Beebe P.S. “The Drag Related Flow Field Characteristics of Trucks and Buses” Aerodynamic Drag Mechanisms of Bluff Bodies and Road Vehicles 45 84 1978
- Roshko, A. “On the Drag and Shedding Frequency of Bluff Cylinders,” 1954
- Bearman, P.W. “The Effect of Base Bleed on the Flow Behind a Two-Dimensional Model with a Blunt Trailing Edge,” Aero. Quart. 1967 18 207 224
- Salari, K. Rutledge, W. McBride, D. “Computational Prediction of Aerodynamic Drag for a Simplified Truck Geometry,” U.S. DOE Third Workshop on Heavy Vehicle Aerodynamics November 1999
- Storms, B.L Heineck, J.T. walker, S.M. Ross, J.C. Driver, D. Bell, J. “Experimental Measurements of the 1/8 th -Scale Ground Transportation System in the NASA Ames 7-by 10-Ft Wind Tunnel,” U. S. DOE Third Workshop on Heavy Vehicle Aerodynamics November 1999
- Nash, J.F. Quiency, V.G. Callinan, J. “Experiments on Two-Dimensional Base Flow at Subsonic and Transonic Speeds,”
- Tanner, M. “A method for Reducing the Base Drag of Wings with Blunt Trailing Edge,” Aero. Quart. 1972 23 15 23
- Han, T. “Computational Analysis of Three-Dimensional Turbulent flow Around a Bluff Body in Ground Proximity,” AIAA Journal 27 9 September 1989
- Duell, E.G. George, A.R. “Measurements in the Unsteady Near Wakes of Ground Vehicle Bodies,” SAE Paper 930298 1993
- Duell, E.G. George, A R. “Unsteady Wake Flows of Ground Vehicle Bodies,” AIAA Paper 92-2641, AIAA 10 th Applied Aerodynamics Conference June 1992
- Hucho, W-H. “Aerodynamics of Road Vehicles,” SAE International Fourth 1998
- Ahmed, S.R. Ramm, G. Faltin, G. “Some Salient Features of the Time Averaged Ground Vehicle Wake,” SAE Paper 840300 1984
- Morel, T. “The Effect of Base-Slant on the Flow Pattern and Drag of Three-Dimensional Bodies,” Aerodynamic Drag Mechanisms of Bluff Bodies and Road Vehicles, Proc. Of Symposium at GMRL 1976
- Lanse, W.R. Ross, J.C. Kaufman, A.E. “Aerodynamic Performance of a Drag Reduction Device on a Full-Scale Tractor/Trailer,” SAE Paper 912125 1991
- Mair, W.A. “Reduction of Base Drag by Boat-Tailed Afterbodies in Low Speed Flow,” Aero. Quart. 1969 20 307 320
- Balkanyi, S.R. Bernal, L. P. Khalighi, B. Sumantran, V. “Dynamics of Manipulated Bluff Body Wakes,” AIAA-2000-2556 Denver, CO 19-22 June 2000
- Haworth, D.C. El Tahry, S.H. Huebler, M.S. Chang, S. “Multidimensional Port-and-Cylinder-Flow Calculations for Two-and Four-Valve-per-Cylinder Engines: Influence of Intake Configuration on Flow Structure,” SAE Paper 900257 1990
- Khalighi, B. El Tahry, S.H. Haworth, D.C. Huebler, M.S. “Computation and Measurement of Flow and Combustion in Four-Valve Engine with Intake Variation,” SAE Paper no. 950287 1995
- Durbin, P.A. “Separated Flow Computations with the k -ε - v 2 Model” AIAA J. 33 659 664 1995