Hostname: page-component-745bb68f8f-kw2vx Total loading time: 0 Render date: 2025-01-09T14:44:48.288Z Has data issue: false hasContentIssue false
  • English
  • Français

Manipulation of three-dimensional asymmetries of a turbulent wake for drag reduction

Published online by Cambridge University Press:  04 February 2021

Yann Haffner Open the ORCID record for Yann Haffner [Opens in a new window] ,
Thomas Castelain ,
Jacques Borée  and
Andreas Spohn
Yann Haffner*
Affiliation:
Département Fluides Thermique et Combustion, Institut Pprime – UPR 3346, CNRS-ENSMA-Université de Poitiers, 86360Futuroscope-Chasseneuil, France
Thomas Castelain
Affiliation:
UDL, Université Claude Bernard Lyon I, Ecole Centrale de Lyon, INSA Lyon, CNRS-LMFA UMR 5509, 69100Villeurbanne, France
Jacques Borée
Affiliation:
Département Fluides Thermique et Combustion, Institut Pprime – UPR 3346, CNRS-ENSMA-Université de Poitiers, 86360Futuroscope-Chasseneuil, France
Andreas Spohn
Affiliation:
Département Fluides Thermique et Combustion, Institut Pprime – UPR 3346, CNRS-ENSMA-Université de Poitiers, 86360Futuroscope-Chasseneuil, France
*
Email address for correspondence: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

Combinations of passive and active flow control are used to reduce the aerodynamic drag of a three-dimensional blunt body by manipulating its large-scale wake asymmetries. An Ahmed-like body with a square-back is mounted in ground proximity in the test section of a wind tunnel to produce a canonical turbulent wake at $Re_H = 5 \times 10^5$ based on the height $H$ of the body. By using passive perturbations around the model, the large-scale asymmetry and dynamics of the unforced recirculation region are modified. Depending on the unforced wake equilibrium, additional high-frequency pulsed blowing, coupled with small curved deflecting surfaces along selected edges of the base, produces a very different impact on the drag. On the one hand, forcing the wake along all edges results in important drag reduction of up to 12 % through a wake-shaping mechanism with weak influence on the large-scale asymmetry. On the other hand, the reorganization of the recirculation region equilibrium plays a key role in the observed drag changes when the wake is only forced along some edges of the base. In particular, the symmetrization of the mean wake and the influence of forcing on the interaction mechanism between facing shear layers described by Haffner et al. (J. Fluid Mech., vol. 894, 2020, A14) appears to be one of the main mechanisms involved in drag reduction. Even if asymmetric forcing strategies resulting in symmetrization of the mean wake provide more modest drag reductions of up to 7 % compared with forcing around the whole base, they are more efficient from an energetic point of view. This study provides key ingredients to adapt forcing strategies for drag reduction in the presence of various wake asymmetries typically imposed in real flow conditions around ground vehicles.

JFM classification

Flow Control: Drag reduction Wakes/Jets: Separated flows Wakes/Jets: Wakes
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 912 , 10 April 2021 , A6
Check for updates
Copyright
© The Author(s), 2021. Published by Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Footnotes

†

Present address: Centre Scientifique et Technique du Bâtiment, Direction Climatologie Aérodynamique Pollution et Epuration, 44323 Nantes, France.

References

REFERENCES

Ahmed, S.R., Ramn, G. & Faltin, G. 1984 Some salient features of the time averaged ground vehicle wake. Tech. Rep. 840300. SAE International.CrossRefGoogle Scholar
Barros, D., Borée, J., Cadot, O., Spohn, A. & Noack, B.R. 2017 Forcing symmetry exchanges and flow reversals in turbulent wakes. J. Fluid Mech. 829, R1.CrossRefGoogle Scholar
Barros, D., Borée, J., Noack, B.R., Spohn, A. & Ruiz, T. 2016 Bluff body drag manipulation using pulsed jets and Coanda effect. J. Fluid Mech. 805, 422–459.Google Scholar
Bonnavion, G. & Cadot, O. 2018 Unstable wake dynamics of rectangular flat-backed bluff bodies with inclination and ground proximity. J. Fluid Mech. 854, 196–232.Google Scholar
Bonnavion, G. & Cadot, O. 2019 Boat-tail effects on the global wake dynamics of a flat-backed body with rectangular section. J. Fluids Struct. 89, 61–71.CrossRefGoogle Scholar
Brackston, R.D., De La Cruz, J.M.G., Wynn, A., Rigas, G. & Morrison, J.F. 2016 Stochastic modelling and feedback control of bistability in a turbulent bluff body wake. J. Fluid Mech. 802, 726–749.CrossRefGoogle Scholar
Cabitza, S. 2015 Active control of the wake from a rectangular-sectioned body. PhD thesis, Imperial College London.Google Scholar
Cadot, O., Evrard, A. & Pastur, L. 2015 Imperfect supercritical bifurcation in a three-dimensional turbulent wake. Phys. Rev. E 91, 063005.CrossRefGoogle Scholar
Castelain, T., Michard, M., Szmigiel, M., Chacaton, D. & Juvé, D. 2018 Identification of flow classes in the wake of a simplified truck model depending on the underbody velocity. J. Wind Engng Ind. Aerodyn. 175, 352–363.CrossRefGoogle Scholar
Choi, H., Jeon, W.P. & Kim, J. 2008 Control of flow over a bluff body. Annu. Rev. Fluid Mech. 40, 113–139.Google Scholar
Dalla Longa, L., Evstafyeva, O. & Morgans, A.S. 2019 Simulations of the bi-modal wake past three-dimensional blunt bluff bodies. J. Fluid Mech. 866, 791–809.CrossRefGoogle Scholar
De La Cruz, J.M.G., Brackston, R.D. & Morrison, J.F. 2017 a Adaptive base-flaps under variable cross-wind. Tech. Rep. 2017-01-7000. SAE International.Google Scholar
De La Cruz, J.M.G., Oxlade, A.R. & Morrison, J.F. 2017 b Passive control of base pressure on an axisymmetric blunt body using a perimetric slit. Phys. Rev. Fluids 2, 043905.CrossRefGoogle Scholar
D'Hooge, A., Rebbeck, L., Palin, R., Murphy, Q., Gargoloff, J. & Duncan, B. 2015 Application of real-world wind conditions for assessing aerodynamic drag for on-road range prediction. Tech. Rep. 2015-01-1551. SAE International.Google Scholar
Evrard, A., Cadot, O., Herbert, V., Ricot, D., Vigneron, R. & Délery, J. 2016 Fluid force and symmetry breaking modes of a 3D bluff body with a base cavity. J. Fluids Struct. 61, 99–114.CrossRefGoogle Scholar
Evstafyeva, O., Morgans, A.S. & Dalla Longa, L. 2017 Simulation and feedback control of the Ahmed body flow exhibiting symmetry breaking behaviour. J. Fluid Mech. 817, R2.CrossRefGoogle Scholar
Fabre, D., Auguste, F. & Magnaudet, J. 2008 Bifurcations and symmetry breaking in the wake of axisymmetric bodies. Phys. Fluids 20, 1–4.CrossRefGoogle Scholar
Freund, J.B. & Mungal, M.G. 1994 Drag and wake modification of axisymmetric bluff bodies using Coanda blowing. J. Aircraft 31 (3), 572–578.Google Scholar
Gentile, V., Van Oudheusden, B., Schrijer, F. & Scarano, F. 2017 The effect of angular misalignment on low-frequency axisymmetric wake instability. J. Fluid Mech. 813, R3.Google Scholar
Grandemange, M., Gohlke, M. & Cadot, O. 2012 Reflectional symmetry breaking of the separated flow over three-dimensional bluff bodies. Phys. Rev. E 86, 035302(R).Google ScholarPubMed
Grandemange, M., Gohlke, M. & Cadot, O. 2013 a Bi-stability in the wake past parallelepiped bodies with various aspect ratios and wall effects. Phys. Fluids 25 (9), 095103.Google Scholar
Grandemange, M., Gohlke, M. & Cadot, O. 2013 b Turbulent wake past a three-dimensional blunt body. Part 1. Global modes and bi-stability. J. Fluid Mech. 722, 51–84.Google Scholar
Grandemange, M., Gohlke, M. & Cadot, O. 2014 Turbulent wake past a three-dimensional blunt body. Part 2. Experimental sensitivity analysis. J. Fluid Mech. 752, 439–461.CrossRefGoogle Scholar
Grandemange, M., Mary, A., Gohlke, M. & Cadot, O. 2013 c Effect on drag of the flow orientation at the base separation of a simplified blunt road vehicle. Exp. Fluids 54, 1529.Google Scholar
Haffner, Y. 2020 Manipulation of three-dimensional turbulent wakes for aerodynamic drag reduction. PhD thesis, Ecole Nationale Supérieure de Mécanique et d'Aérotechnique (ENSMA).Google Scholar
Haffner, Y., Borée, J., Spohn, A. & Castelain, T. 2020 a Mechanics of bluff body drag reduction during transient near wake reversals. J. Fluid Mech. 894, A14.Google Scholar
Haffner, Y., Borée, J., Spohn, A. & Castelain, T. 2020 b Unsteady Coanda effect and drag reduction for a turbulent wake. J. Fluid Mech. 899, A36.CrossRefGoogle Scholar
Haffner, Y., Mariette, K., Bideaux, E., Borée, J., Eberard, D., Castelain, T., Bribiesca-Argomedo, F., Spohn, A., Michard, M. & Sesmat, S. 2020 c Large-scale asymmetries of a turbulent wake: insights and closed-loop control for drag reduction. In 55th 3AF International Conference on Applied Aerodynamics.Google Scholar
Li, R., Barros, D., Borée, J., Cadot, O., Noack, B.R. & Cordier, L. 2016 Feedback control of bimodal wake dynamics. Exp. Fluids 57, 158.CrossRefGoogle Scholar
Li, R., Borée, J., Noack, B.R., Cordier, L. & Harambat, F. 2019 Drag reduction mechanisms of a car model at moderate yaw by bi-frequency forcing. Phys. Rev. Fluids 4, 034604.CrossRefGoogle Scholar
Lorite-Díez, M., Jimenéz-González, J.I., Pastur, L., Martńez-Bazán, C. & Cadot, O. 2020 Experimental analysis of the effect of local base blowing on three-dimensional wake modes. J. Fluid Mech. 883, A53.Google Scholar
Lucas, J.-M., Cadot, O., Herbert, V., Parpais, S. & Délery, J. 2017 A numerical investigation of the asymmetric wake mode of a squareback Ahmed body – effect of a base cavity. J. Fluid Mech. 831, 675–697.CrossRefGoogle Scholar
Mariette, K., Bideaux, E., Bribiesca-Argomedo, F., Ebérard, D., Sesmat, S., Haffner, Y., Borée, J., Castelain, T. & Michard, M. 2020 Wake symmetrisation of a bluff Ahmed body based on sliding mode control. In 21st IFAC World Congress.Google Scholar
Oxlade, A. 2013 High-frequency pulsed jet forcing of an axisymmetric bluff body wake. PhD thesis, Imperial College London.Google Scholar
Oxlade, A.R., Morrison, J.F., Qubain, A. & Rigas, G. 2015 High-frequency forcing of a turbulent axisymmetric wake. J. Fluid Mech. 770, 305–318.CrossRefGoogle Scholar
Pfeiffer, J. & King, R. 2012 Multivariable closed-loop flow control of drag and yaw moment for a 3D bluff body. In 6th AIAA Flow Control Conference, doi:10.2514/6.2012-2802. American Institute of Aeronautics and Astronautics.CrossRefGoogle Scholar
Pier, B. 2008 Local and global instabilities in the wake of a sphere. J. Fluid Mech. 603, 39–61.CrossRefGoogle Scholar
Rigas, G., Morgans, A.S., Brackston, R.D. & Morrison, J.F. 2015 Diffusive dynamics and stochastic models of turbulent axisymmetric wakes. J. Fluid Mech. 778, R2.CrossRefGoogle Scholar
Rigas, G., Oxlade, A.R., Morgans, A.S. & Morrison, J.F. 2014 Low-dimensional dynamics of a turbulent axisymmetric wake. J. Fluid Mech. 755, R5.CrossRefGoogle Scholar
Spohn, A. & Gilliéron, P. 2002 Flow separations generated by a simplified geometry of an automotive vehicle. In IUTAM Symposium: Unsteady Separated Flows, pp. 8–12. International Union for Theoretical and Applied Mechanics.Google Scholar
Sujar-Garrido, P., Michard, M., Castelain, T. & Haffner, Y. 2019 Identification of efficient flow control strategies for truck model drag reduction. In 11th International Symposium on Turbulence and Shear Flow Phenomena (TSFP11), http://www.tsfp-conference.org/proceedings/2019/244.pdf.Google Scholar
Szmigiel, M. 2017 Effet du flux de soubassement sur la dynamique du sillage d'un corps non profilé à culot droit: application du contrôle actif pour la réduction de traînée de véhicule industriel. PhD thesis, Ecole Centrale de Lyon.Google Scholar
Wong, D.T.-M. & Mair, W.A. 1983 Boat-tailed afterbodies of square section as drag-reduction devices. J. Wind Engng Ind. Aerodyn. 611, 1–11.Google Scholar