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Relationship between the base pressure and the velocity in the near-wake of an Ahmed body

Bérengère Podvin

Stéphanie Pellerin and Yann Fraigneau

Guillaume Bonnavion

Olivier Cadot

  • EM2C, CentraleSupélec, CNRS, Université Paris-Saclay, 91190 Gif/Yvette, France

  • LISN, CNRS, Université Paris-Saclay, 91190 Gif/Yvette, France

  • École Nationale Supérieure de Mécanique et d'Aérotechnique, 1 Av. Clément Ader, 86360 Chasseneuil-du-Poitou, France

  • School of Engineering, University of Liverpool, L69 3BX Brownlow Hill, Liverpool L69 3GH, United Kingdom

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Phys. Rev. Fluids 7, 054602 – Published 9 May, 2022

DOI: https://doi.org/10.1103/PhysRevFluids.7.054602

Abstract

We investigate the near-wake flow of an Ahmed body which is characterized by switches between two asymmetric states that are mirrors of each other in the spanwise direction. The work focuses on the relationship between the base pressure distribution and the near-wake velocity field. Using direct numerical simulation obtained at a Reynolds number of 104 based on incoming velocity and body height as well as Bonnavion and Cadot's experiment [G. Bonnavion and O. Cadot, J. Fluid Mech. 854, 196 (2018)], we perform proper orthogonal decomposition (POD) of the base pressure field. The signature of the switches is given by the amplitude of the most energetic, antisymmetric POD mode. However, switches are also characterized by a global base suction decrease, as well as deformations in both vertical and lateral directions, which all correspond to large-scale symmetric modes. Most of the base suction reduction is due to the two most energetic symmetric modes. Using the linear stochastic estimation technique of Podvin et al. [Exp. Fluids 59, 58 (2018)], we show that the large scales of the near-wake velocity field can be recovered to some extent from the base pressure modes. Conversely, it is found that the dominant pressure modes and the base suction fluctuation can be well estimated from the POD velocity modes of the near-wake.

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References (36)

  1. M. Grandemange, M. Gohlke, and O. Cadot, Turbulent wake past a three-dimensional blunt body. Part 1. Global modes and bi-stability, J. Fluid Mech. 722, 51 (2013).
  2. D. Barros, T. Ruiz, J. Borée, and B. Noack, Control of three-dimensional blunt body wake using low and high frequency pulsed jets, Int. J. Flow Control 6, 61 (2014).
  3. R. Li, D. Barros, J. Borée, O. Cadot, B. Noack, and L. Cordier, Feedback control of bimodal wake dynamics, Exp. Fluid 51, 158 (2016).
  4. A. Evrard, O. Cadot, V. Herbert, D. Ricot, R. Vigneron, and J. Delery, Fluid force and symmetry breaking modes of a 3D bluff body with a base cavity, J. Fluids Struct. 61, 99 (2016).
  5. R. Brackston, J. G. D. L. Cruz, A. Wynn, G. Rigas, and J. Morrison, Stochastic modelling and feedback control of bistability in a turbulent bluff body wake, J. Fluid Mech. 802, 726 (2016).
  6. B. Plumejeau, S. Delpart, L. Keirsbulck, M. Lippert, and W. Abassi, Ultra-local model-based control of the square-back Ahmed body wake flow, Phys. Fluids 31, 085103 (2019).
  7. G. Pavia, M. Passmore, and C. Sardu, Evolution of the bi-stable wake of a square-back automotive shape, Exp. Fluids 59, 2742 (2018).
  8. A. Perry, G. Pavia, and M. Passmore, Influence of short rear end tapers on the wake of a simplified square-back vehicle: Wake topology and rear drag, Exp. Fluids 57, 169 (2016).
  9. J. Lucas, O. Cadot, V. Herbert, S. Parpais, and J. Délery, A numerical investigation of the asymmetric wake mode of a squareback Ahmed body – Effect of a base cavity, J. Fluid Mech. 831, 675 (2017).
  10. O. Evsafyeva, A. Morgans, and L. D. Longa, Simulation and feedback control of the Ahmed body flow exhibiting symmetry breaking behaviour, J. Fluid Mech. 817, R2 (2017).
  11. A. Rao, G. Minelli, B. Basara, and S. Krajnovic, On the two flow states in the wake of a hatchback Ahmed body, J. Wind Eng. Ind. Aerodyn. 173, 262 (2018).
  12. L. Dalla Longa, O. Evstafyeva, and A. S. Morgans, Simulations of the bi-modal wake past three-dimensional blunt bluff bodies, J. Fluid Mech. 866, 791 (2019).
  13. Y. Fan, X. Chao, S. Chu, Z. Yang, and O. Cadot, Experimental and numerical analysis of the bi-stable turbulent wake of a rectangular flat-backed bluff body, Phys. Fluids 32, 105111 (2020).
  14. R. Adrian and P. Moin, Stochastic estimation of organized turbulent structure: Homogeneous shear flow, J. Fluid Mech. 190, 531 (1988).
  15. J. Taylor and M. Glauser, Towards practical flow sensing and control via POD and LSE-based low-dimensional tools, in ASME 2002 Fluids Engineering Division Summer Meeting, Montreal, Quebec, 14–18 July 2002 (ASME, New York, 2002).
  16. J. Bonnet, D. Cole, J. Delville, M. Glauser, and L. Ukeiley, Stochastic estimation and proper orthogonal decomposition: Complementary techniques for identifying structure, Exp. Fluids 17, 307 (1994).
  17. J. Boree, Extended proper orthogonal decomposition: A tool to analyse correlated events in turbulent flows, Exp. Fluids 35, 188 (2003).
  18. J. Citriniti and W. George, Reconstruction of the global velocity field in the axisymmetric mixing layer utilizing the proper orthogonal decomposition, J. Fluid Mech. 418, 137 (2000).
  19. C. Tinney, F. Coiffet, J. Delville, A. Hall, P. Jordan, and M. Glauser, On spectral linear stochastic estimation, Exp. Fluids 41, 763 (2007).
  20. L. Hudy and A. Naguib, Stochastic estimation of a separated-flow field using wall-pressure-array measurements, Phys. Fluids 19, 024103 (2007).
  21. D. Lasagna, M. Orazi, and G. Iuso, Multi-time delay, multi-point linear stochastic estimation of a cavity shear layer velocity from wall-pressure measurements, Phys. Fluids 25, 017101 (2013).
  22. V. Durgesh and J. Naughton, Multi-time delay, multi-point linear stochastic estimation of a cavity shear layer velocity from wall-pressure measurements, Exp. Fluids 49, 571 (2010).
  23. B. Podvin, S. Nguimatsia, J. Foucaut, C. Cuvier, and Y. Fraigneau, On combining linear stochastic estimation and proper orthogonal decomposition for flow reconstruction, Exp. Fluids 59, 58 (2018).
  24. P. A. Chang III, U. Piomelli, and W. Blake, Relationship between wall pressure and velocity-field sources, Phys. Fluids 11, 3434 (1999).
  25. M. Ferreira and B. Ganapathisubramani, Scale interactions in velocity and pressure within a turbulent boundary layer developing over a staggered-cube array, J. Fluid Mech. 910, A48 (2021).
  26. B. Podvin, S. Pellerin, Y. Fraigneau, G. Bonnavion, and O. Cadot, Low-order modelling of the wake dynamics of an Ahmed body, J. Fluid Mech. 927, R6 (2021).
  27. G. Bonnavion and O. Cadot, Unstable wake dynamics of rectangular flat-backed bluff bodies with inclination and ground proximity, J. Fluid Mech. 854, 196 (2018).
  28. K. Goda, A multistep technique with implicit difference schemes for calculating two- or three-dimensional cavity flows, J. Comput. Phys. 30, 76 (1979).
  29. L. Sirovich, Turbulence and the dynamics of coherent structures. Part I: Coherent structures, Quart. Appl. Math. 45, 561 (1987).
  30. S. Pope, Turbulent Flows (Cambridge University Press, Cambridge, England, 2000).
  31. P. Holmes, J. Lumley, and G. Berkooz, Turbulence, Coherent Structures, Dynamical Systems and Symmetry (Cambridge University Press, Cambridge, England, 1996).
  32. P. Moin and R. Moser, Characteristic-eddy decomposition of turbulence in a channel, J. Fluid Mech. 200, 471 (1989).
  33. S. Muralidhar, B. Podvin, L. Mathelin, and Y. Fraigneau, Spatio-temporal proper orthogonal decomposition of turbulent channel flow, J. Fluid Mech. 864, 614 (2019).
  34. L. Soucasse, B. Podvin, P. Rivière, and A. Soufiani, Proper orthogonal decomposition analysis and modelling of large-scale flow reorientations in a cubic Rayleigh-Bénard cell, J. Fluid Mech. 881, 23 (2019).
  35. B. Podvin, S. Pellerin, Y. Fraigneau, A. Evrard, and O. Cadot, Proper orthogonal decomposition analysis and modelling of the wake deviation behind a squareback Ahmed body, Phys. Rev. Fluids 5, 064612 (2020).
  36. J. Lumley, The structure of inhomogeneous turbulent flows, in Atmospheric Turbulence and Radio Wave Propagation, edited by A. Iaglom and V. Tatarski (Nauka, Moscow, 1967), pp. 221–227.

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Phys. Rev. Fluids 7, 054602– Published 9 May, 2022
  • Received 30 November 2021
  • Accepted 20 April 2022
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