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High-frequency forcing of a turbulent axisymmetric wake

Published online by Cambridge University Press:  31 March 2015

Anthony R. Oxlade ,
Jonathan F. Morrison ,
Ala Qubain  and
Georgios Rigas
Anthony R. Oxlade
Affiliation:
Department of Aeronautics, Imperial College, London SW7 2AZ, UK
Jonathan F. Morrison*
Affiliation:
Department of Aeronautics, Imperial College, London SW7 2AZ, UK
Ala Qubain
Affiliation:
Mustakbal Clean Tech, PO Box 5272, Amman 11183, Jordan
Georgios Rigas
Affiliation:
Department of Aeronautics, Imperial College, London SW7 2AZ, UK
*
†Email address for correspondence: j.morrison@imperial.ac.uk
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Abstract

A high-frequency periodic jet, issuing immediately below the point of separation, is used to force the turbulent wake of a bluff axisymmetric body, its axis aligned with the free stream. It is shown that the base pressure may be varied more or less at will: at forcing frequencies several times that of the shear layer frequency, the time-averaged area-weighted base pressure increases by as much as 35 %. An investigation of the effects of forcing is made using random and phase-locked two-component particle image velocimetry (PIV), and modal decomposition of pressure fluctuations on the base of the model. The forcing does not target specific local or global wake instabilities: rather, the high-frequency jet creates a row of closely spaced vortex rings, immediately adjacent to which are regions of large shear on each side. These shear layers are associated with large dissipation and inhibit the entrainment of fluid. The resulting pressure recovery is proportional to the strength of the vortices and is accompanied by a broadband suppression of base pressure fluctuations associated with all modes. The optimum forcing frequency, at which amplification of the shear layer mode approaches unity gain, is roughly five times the shear layer frequency.

JFM classification

Flow Control: Instability control Turbulent Flows: Turbulence control Wakes/Jets: Wakes
Type
Papers
Information
Journal of Fluid Mechanics , Volume 770 , 10 May 2015 , pp. 305 - 318
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Copyright
© 2015 Cambridge University Press 

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References

Achenbach, E. 1974 Vortex shedding from spheres. J. Fluid Mech. 62, 209–221.Google Scholar
Adrian, R. J. 1982 Comment on ‘A note on Poisson’s equation for pressure in a turbulent flow’. Phys. Fluids 25, 577.Google Scholar
Barros, D., Ruiz, T., Borée, J. & Noack, B. R. 2014 Control of a three-dimensional blunt body wake using low and high frequency pulsed jets. Intl J. Flow Control 6 (1), 61–74.Google Scholar
Berger, E., Scholz, D. & Schumm, M. 1990 Coherent vortex structures in the wake of a sphere and a circular disk at rest and under forced vibrations. J. Fluids Struct. 4, 231–257.Google Scholar
Bradshaw, P. & Koh, Y. M. 1981 A note on Poisson’s equation for pressure in a turbulent flow. Phys. Fluids 24, 777.Google Scholar
Cabitza, S.2013 Active control of the wake from a rectangular-sectioned body. PhD dissertation, Imperial College, Department of Aeronautics.Google 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
Corrsin, S. & Kistler, A. L.1955 Free-stream boundaries of turbulent flows. NACA Tech. Rep. TN-1244.Google Scholar
Dahan, J. A., Morgans, A. S. & Lardeau, S. 2012 Feedback control for form-drag reduction on a bluff body with a blunt trailing edge. J. Fluid Mech. 704, 360–387.Google Scholar
Fuchs, H. V., Mercker, E. & Michel, U. 1979 Large-scale coherent structures in the wake of axisymmetric bodies. J. Fluid Mech. 93, 185–207.Google Scholar
Gaster, M., Kit, E. & Wygnanski, I. 1985 Large-scale structures in a forced turbulent mixing layer. J. Fluid Mech. 150, 23–39.Google Scholar
Gerrard, J. H. 1966 The mechanics of the formation region of vortices behind bluff bodies. J. Fluid Mech. 25 (2), 401–413.Google Scholar
Glezer, A. & Amitay, M. 2002 Synthetic jets. Annu. Rev. Fluid Mech. 34, 503–529.CrossRefGoogle Scholar
Grandemange, M., Gohlke, M. & Cadot, O. 2013 Turbulent wake past a three-dimensional blunt body. Part 1. Global modes and bi-stability. J. Fluid Mech. 722, 51–84.Google Scholar
Heenan, A. F. & Morrison, J. F. 1996 Passive control of backstep flow. Exp. Therm. Fluid Sci. 13, 211–222.Google Scholar
Heenan, A. F. & Morrison, J. F. 1998 Passive control of pressure fluctuations generated by separated flow. AIAA J. 36, 1014–1022.Google Scholar
Ho, C.-M. & Huerre, P. 1984 Perturbed free shear layers. Annu. Rev. Fluid Mech. 463, 365–424.Google Scholar
Huerre, P. 2000 Open shear flow instabilities. In Perspectives in Fluid Dynamics (ed. Batchelor, G. K., Moffatt, H. K. & Worster, M. G.). Cambridge University Press.Google Scholar
Kang, S. & Choi, H. 2002 Suboptimal feedback control of turbulent flow over a backward facing step. J. Fluid Mech. 463, 201–227.Google Scholar
Kim, J. & Choi, H. 2005 Distributed forcing of flow over a circular cylinder. Phys. Fluids 17, 033103.Google Scholar
Monkewitz, P. A. 1988 A note on vortex shedding from axisymmetric bluff bodies. J. Fluid Mech. 192, 561–575.Google Scholar
Morrison, J. F. & Qubain, A. 2009 Control of an axisymmetric turbulent wake by a pulsed jet. In Advances in Turbulence XII: Proceedings of the 12th EUROMECH European Turbulence Conference (ed. Eckhardt, B.), Springer Proceedings in Physics, vol. 132, pp. 225–228. Springer.Google Scholar
Oxlade, A. R.2013 High-frequency periodic jet forcing of a turbulent axisymmetric wake. PhD dissertation, Imperial College, Department of Aeronautics.Google Scholar
Oxlade, A. R., Valente, P. C., Ganapathisubramani, B. & Morrison, J. F. 2012 Denoising of time-resolved PIV for accurate measurement of turbulence spectra and reduced error in derivatives. Exp. Fluids 53, 1561–1575.Google Scholar
Parezanovic, V. & Cadot, O. 2012 Experimental sensitivity analysis of the global properties of a two-dimensional turbulent wake. J. Fluid Mech. 693, 115–149.Google Scholar
Philip, J. & Marusic, I. 2012 Large-scale eddies and their role in entrainment in turbulent jets and wakes. Phys. Fluids 24, 055108.Google Scholar
Qubain, A.2007 Separated shear flow manipulation using periodic forcing. Transfer Report, Imperial College, Department of Aeronautics.Google Scholar
Qubain, A.2009 Active control of a turbulent bluff body wake. PhD dissertation, Imperial College, Department of Aeronautics.Google Scholar
Qubain, A. & Morrison, J. F. 2009 Control of an axisymmetric turbulent wake by a pulsed jet. In 12th EUROMECH European Turbulence Conference, pp. 225–228. Springer.Google Scholar
Raffel, M., Willert, C., Wereley, S. & Kompenhans, J. 2007 Particle Image Velocimetry: A Practical Guide, 2nd edn. Springer.Google Scholar
Rigas, G., Morgans, A. S., Brackston, R. D. & Morrison, J. F.2014a Diffusive dynamics of turbulent axisymmetric wake flows (in preparation).Google Scholar
Rigas, G., Oxlade, A. R., Morgans, A. S. & Morrison, J. F. 2014b Low-frequency dynamics of a turbulent axisymmetric wake. J. Fluid Mech. 755, R5.Google Scholar
Roshko, A. 1993 Perspectives on bluff body aerodynamics. J. Wind Engng Ind. Aerodyn. 49, 79–100.Google Scholar
Strykowski, P. J. & Sreenivasan, K. R. 1990 On the formation and suppression of vortex ‘shedding’ at low Reynolds numbers. J. Fluid Mech. 218, 71–107.Google Scholar
Taneda, S. 1978 Visual observations of the flow past a sphere at Reynolds numbers between $10^{4}$ and $10^{6}$ . J. Fluid Mech. 85, 187–192.Google Scholar
Townsend, A. A. 1976 The Structure of Turbulent Shear Flow, 2nd edn. Cambridge University Press.Google Scholar
Turner, J. S. 1986 Turbulent entrainment: the development of the entrainment assumption, and its application to geophysical flows. J. Fluid Mech. 173, 431–471.Google Scholar
Vukasinovic, B., Rusak, Z. & Glezer, A. 2010 Dissipative small-scale actuation of a turbulent shear layer. J. Fluid Mech. 656, 51–81.Google Scholar
Westerweel, J., Kukushima, C., Pedersen, J. M. & Hunt, J. C. R. 2005 Mechanics of the turbulent–nonturbulent interface of a jet. Phys. Rev. Lett. 95, 174501.Google Scholar
Zaman, K. B. M. Q. & Hussain, A. K. M. F. 1981 Turbulence suppression in free shear flows by controlled excitation. J. Fluid Mech. 103, 133–159.Google Scholar