Skip to main content

Drag reduction on the 25° slant angle Ahmed reference body using pulsed jets


This paper highlights steady and unsteady measurements and flow control results obtained on an Ahmed model with slant angle of 25° in wind tunnel. On this high-drag configuration characterized by a large separation bubble along with energetic streamwise vortices, time-averaged and time-dependent results without control are first presented. The influence of rear-end periodic forcing on the drag coefficient is then investigated using electrically operated magnetic valves in an open-loop control scheme. Four distinct configurations of flow control have been tested: rectangular pulsed jets aligned with the spanwise direction or in winglets configuration on the roof end and rectangular jets or a large open slot at the top of the rear slant. For each configuration, the influence of the forcing parameters (non-dimensional frequency, injected momentum) on the drag coefficient has been studied, along with their impact on the static pressure on both the rear slant and vertical base of the model. Depending on the type and location of pulsed jets actuation, the maximum drag reduction is obtained for increasing injected momentum or well-defined optimal pulsation frequencies.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11
Fig. 12
Fig. 13
Fig. 14
Fig. 15
Fig. 16
Fig. 17
Fig. 18
Fig. 19
Fig. 20
Fig. 21
Fig. 22
Fig. 23
Fig. 24
Fig. 25


  • Ahmed SR, Ramm G, Faltin G (1984) Some salient features of the time-averaged ground vehicle wake. SAE 840300

  • Aider JL, Danet A, Lesieur M (2007) Large-eddy simulation applied to study the influence of upstream conditions on the time-dependant and averaged characteristics of a backward-f acing step flow. J Turbul 8:N51

    Article  Google Scholar 

  • Aider JL, Beaudoin JF, Wesfreid JE (2009) Drag and lift reduction of a 3D bluff-body using active vortex generators. Exp Fluids 48:771–789

    Article  Google Scholar 

  • Barnard RH (1996) Road vehicle aerodynamic design: an introduction. Longman, Essex

    Google Scholar 

  • Beaudoin JF, Aider JL (2008) Drag and lift reduction of 3D bluff-body using flaps. Exp Fluids 44:491–501

    Article  Google Scholar 

  • Beaudoin JF, Aider JL, Cadot O, Gosse K, Paranthoen P, Hamelin B, Tissier M, Wesfreid JE (2004) Characterization of longitudinal vortices on a 3D bluff-body using cavitation. Exp Fluids 37:763–768

    Article  Google Scholar 

  • Beaudoin JF, Cadot O, Wesfreid JE, Aider JL (2008) Feedback control using extremum seeking method for drag reduction of a 3D bluff body. In: IUTAM symposium on flow control and MEMS, London

  • Brunn A, Nitsche W, Henning L, King R (2008) Application of Slope-seeking to a Generic Car Model for Active Drag Control. In: 26th AIAA applied aerodynamics conference, Honolulu

  • Cherry NJ, Hillier R, Latour MEMP (1984) Unsteady measurements in a separated and reattaching flow. J Fluid Mech 144:13–46

    Article  Google Scholar 

  • Cortelezzi L, Karagozian AR (2001) On the formation of the counter-rotating vortex pair in transverse jets. J Fluid Mech 446:347–373

    MathSciNet  MATH  Google Scholar 

  • Duriez T, Aider JL, Wesfreid JE (2006) Base flow modification by streamwise vortices. Application to the control of separated flows. In: ASME Joint U.S.—European fluids engineering summer meeting, Miami

  • Duriez T, Aider JL, Wesfreid JE (2008a) Control of a separated flow over a smoothly contoured ramp using vortex generators. In: IUTAM symposium on flow control and MEMS, London

  • Duriez T, Aider JL, Wesfreid JE (2008b) Non-linear modulation of a boundary layer induced by vortex generators. AIAA 2008-4076

  • Fares E (2006) Unsteady flow simulation of the Ahmed reference body using a lattice Boltzmann approach. Comput Fluids 35:940–950

    Article  MATH  Google Scholar 

  • Fourrié G, Keirsbulck L, Labraga L, Gilliéron P (2011) Bluff-body drag reduction using a deflector. Exp Fluids 50:385–395

    Article  Google Scholar 

  • Gilliéron P (2000) La technique des visualisations pariétales. Lesson, Conservatoire National des Arts et Métiers

  • Gilliéron P (2010) Influence of the slant angle of 3D bluff-bodies on longitudinal vortex formation. J Fluids Eng 132(051104–1):051104–051109

    Article  Google Scholar 

  • Ho CM, Huerre P (1984) Perturbed free shear layers. Ann Rev Fluid Mech 16:365–424

    Article  Google Scholar 

  • Hucho WH (1998) Aerodynamics of road vehicles. Cambridge University Press, Cambridge

    Google Scholar 

  • Kiya M, Sasaki K (1985) Structure of large scale vortices and unsteady reverse flow in the reattaching zone of a turbulent separation bubble. J Fluid Mech 154:463–491

    Article  Google Scholar 

  • Krajnović S, Davidson L (2005a) Flow around a simplified car, part 1: large eddy simulation. J Fluids Eng 127:907–918

    Article  Google Scholar 

  • Krajnović S, Davidson L (2005b) Flow around a simplified car, part 2: understanding the flow. J Fluids Eng 127:919–928

    Article  Google Scholar 

  • Krajnović S, Östh J, Basara B (2009) LES of active flow control around an Ahmed body with active flow control. In: Conference on modelling fluid flow (CMFF’09), Budapest

  • Krentel D, Mumiovic R, Brunn A, Wolfgang N, King R (2010) Application of active flow control on generic 3D car models. In: King R (ed) Active flow control II 2010. Springer, Berlin

  • Leclerc C (2008) Réduction de la trainée d’un véhicule automobile simplifié à l’aide du contrôle actif par jet synthétique. PhD thesis, Institut National Polytechique de Toulouse

  • Lehugeur B (2009) Contrôle des structures tourbillonnaires longitudinales dans le sillage d’une géométrie simplifiée de véhicule automobile: approche expérimentale. Mech Ind 9:533–541

    Google Scholar 

  • Pastoor M, Henning L, Noack BR, King R, Tadmor G (2008) Feedback shear layer control for bluff body drag reduction. J Fluid Mech 608:161–196

    Article  MATH  Google Scholar 

  • Pujals G, Depardon S, Cossu C (2010) Drag reduction of a 3D bluff-body using coherent streamwise streaks. Exp Fluids 49:1085–1094

    Article  Google Scholar 

  • Rouméas M (2006) Contribution à l’analyse et au contrôle des sillages de corps épais par aspiration ou soufflage continu. PhD thesis, Institut National Polytechnique de Toulouse

  • Rouméas M, Gilliéron P, Kourta A (2008) Drag reduction by flow control on a car after body. Int J Numer Meth Fluids 60:1222–1240

    Article  Google Scholar 

  • Sigurdson LW (1995) The structure and control of a turbulent reattaching flow. J Fluid Mech 298:139–165

    Article  Google Scholar 

  • Thacker A (2010) Contribution expérimentale à l’analyse stationnaire et instationnaire de l’écoulement à l’arrière d’un corps de faible allongement. PhD thesis, Université d’Orléans

  • Thacker A, Leroy A, Aubrun S, Loyer S, Devinant P (2009) Caractéristiques du sillage du corps de Ahmed: effet de la suppression du décollement de lunette arrière. In: GDR 2502 Contrôle des décollements, Orléans

  • Tihon J, Penkavova V, Pantzali M (2010) The effect of inlet pulsations on the backward-facing step flow. E J Mech B Fluids 29:224–235

    Article  MATH  Google Scholar 

  • Vino G, Watkins S, Mousley P, Watmuff J, Prasad S (2005) Flow structures in the near wake of the Ahmed model. J Fluids Struct 20:673–695

    Article  Google Scholar 

Download references


This work was carried out in the framework of the CARAVAJE project supported by the Agence pour le Développement Et la Maîtrise de l’Energie (ADEME). We thank the Renault SA and PSA Peugeot-Citroën Aerodynamics Research teams and the Plastic Omnium research team for fruitful discussions. Technical support by the S4 Wind Tunnel team is also gratefully acknowledged.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Jean-Luc Aider.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Joseph, P., Amandolèse, X. & Aider, JL. Drag reduction on the 25° slant angle Ahmed reference body using pulsed jets. Exp Fluids 52, 1169–1185 (2012).

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: