Automotive Drag Reduction through Distributed Base Roughness Elements

Abstract:

This paper focuses on the effect of base roughness added to the rear of an automotive reference model, the Windsor model. This roughness addition was found to reduce both the drag and the lift of the model. RANS CFD simulations presented here replicate the experimentally observed drag reduction and enable a detailed examination of the mechanisms behind this effect. Investigations into the wake structure of the configurations with base roughness and the baseline case without base roughness showed the main changes to the wake to include a reduction in the overall size of the wake with base roughness present. Furthermore a reduction in the near wall velocities at the rear of the model caused stretching of the upper and lower vortices, a more turbulent near wake and pressure recovery over much of the rear face. This leads to reduce levels of pressure drag on the model.

• Periodical: Applied Mechanics and Materials (Volume 553)
• Pages: 267-272
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.553.267
• Online since: May 2014
• Authors: Iain Robertson*, Adrien Becot, Adrian Gaylard, Ben Thornber
• Keywords: Automotive, Drag Reduction, RANS, Roughness Element, Windsor Body

References

[1] Ford Motor Company Streamlined all-new Ford Focus significantly reduces aerodynamic drag, adding fuel efficiency. http: /media. ford. com/article_display. cfm?article_id=33939 (accessed 28/05/2012).

[2] W. Hucho and G. Sovran, Aerodynamics of road vehicles. Ann. Rev. of Fluid Mech., 25: 1 (1993) 485-537.

DOI: 10.1146/annurev.fl.25.010193.002413

[3] R. Littlewood, M. Passmore and D. Wood, An investigation into the wake structure of square back vehicles and the effect of structure modification on resultant vehicle forces. S. l. : SAE International, (2011) 10. 4271/2011-37-0015.

DOI: 10.4271/2011-37-0015

[4] G. Le Good and K. Garry, On the Use of Reference Models in Automotive Aerodynamics, S. l. : SAE International, (2004) 10. 4271/2004-01-1308.

[5] F.R. Menter, Performance of popular turbulence models for attached and separated adverse pressure gradient flows. AIAA J., 30: 8 (1992) 2068-(2072).

DOI: 10.2514/3.11180

[6] D.C. Wilcox, Reassessment of the scale-determining equation for advanced turbulence models. AIAA J. 26: 11 (1998) 1299-1310.

DOI: 10.2514/3.10041

[7] A-K. Perry and M. Passmore, The impact of underbody roughness on rear wake structure of a squareback vehicle. SAE Technical Paper 2013-01-0463 (2013).

DOI: 10.4271/2013-01-0463

[8] A-K. Perry and M. Passmore, Loughborough University, Personal communication, 10th July (2012).

[9] N. Axelsson, M. Ramnefors, and R. Gustafsson, R., Accuracy in Computational Aerodynamics Part 1: Stagnation Pressure, SAE Technical Paper 980037 (1998).

DOI: 10.4271/980037

[10] A.P. Gaylard, J. Bickerton, J.P. Howell Current issues in the use of CFD to predict aerodynamic characteristics of car shapes. In: 2nd MIRA International Conference on Vehicle Aerodynamics; (1998).

[11] J. Williams, J. Barlow and R. Ranzenbach, Experimental Study of CD Variation With Aspect Ratio, SAE Technical Paper 1999-01-0649 (1999).

DOI: 10.4271/1999-01-0649