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Turbulence measurements around a mild separation bubble and downstream of reattachment

Published online by Cambridge University Press:  26 April 2006

Amy E. Alving  and
H. H. Fernholz
Amy E. Alving
Affiliation:
Aerospace Engineering & Mechanics, University of Minnesota, Minneapolis, MN 55455, USA
H. H. Fernholz
Affiliation:
Hermann-F6ttinger Institut, Technische Universitat Berlin, Germany
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Abstract

This paper describes the behaviour of a turbulent boundary layer on a smooth, axisymmetric body exposed to an adverse pressure gradient of sufficient strength to cause a short region of mean reverse flow ('separation’). The pressure distribution is tailored such that the boundary layer reattaches and then develops in a nominally zero pressure gradient. Hot-wire and pulsed-wire measurements are presented over the separated region and downstream of reattachment. The response of the turbulence quantities to separation and to reattachment is discussed, with emphasis on the relaxation behaviour after reattachment. Over the separation bubble, the response is characteristic of that seen by other workers: the Reynolds stresses in the inner region are reduced and stress peaks develop away from the wall. At reattachment, the skewness of the fluctuating wall shear stress vanishes, as it is known to do at separation. After reattachment, the outer-layer stresses decay towards levels typical of unperturbed boundary layers. But the inner-layer relaxation is unusual. As the viscous wall stress increases downstream of reattachment, the recovery does not start at the wall and travel outward via the formation of an ‘internal’ layer, the process observed in many other relaxing flows. In fact, the inner layer responds markedly more slowly than the outer layer, even though response times are shortest near the wall. It is concluded that the large-scale, outer structures in the turbulent boundary layer survive the separation process and interfere with the regeneration of Reynolds stresses in the inner region after reattachment. This behaviour continues for at least six bubble lengths (20 boundary-layer thicknesses) after reattachment and is believed to have profound implications for our understanding of the interaction between inner and outer layers in turbulent boundary layers.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 322 , 10 September 1996 , pp. 297 - 328
Copyright
© 1996 Cambridge University Press

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References

Alving, A. E. 1988 Boundary layer relaxation from convex curvature. PhD dissertation, Princeton University (T-1816, Mechanical and Aerospace Engineering).
Alving, A. E. & Fernholz, H. H. 1995 Mean-velocity scaling in and around a mild, turbulent separation bubble. Phys. Fluids 7, 1956–1969 (referred to herein as AF).Google Scholar
Alving, A. E., Smits, A. J. & Watmuff, J. H. 1990 Turbulent boundary layer relaxation from convex curvature. J. Fluid Mech. 211, 529–556.Google Scholar
Bradbury, L. J. S. & Castro, I. P. 1971 A pulsed-wire technique for velocity measurements in highly turbulent flows. J. Fluid Mech. 49, 657–691.Google Scholar
Chandrsuda, C. & Bradshaw, P. 1981 Turbulence structure of a reattaching mixing layer. J. Fluid Mech. 110, 171–194.Google Scholar
Cherry, N. J., Hillier, R. & Latour, M. E. M. P. 1984 Unsteady measurements in a separated and reattaching flow. J. Fluid Mech. 144, 13–46.Google Scholar
Dengel, P. 1992 über die Struktur und die Sensibilität einer inkompressiblen turbulenten Gren- zschicht am Rande der AblÖsung (Concerning the structure and sensitivity of an incompressible turbulent boundary layer close to separation). Dissertation, Technische Universitat Berlin D83.
Dengel, P. & Fernholz, H. H. 1989 Generation of and measurements in a turbulent boundary layer with zero skin friction. In Advances in Turbulence 2, (ed. H. H. Fernholz & H. E. Fielder), pp. 432–437. Springer (referred to herein as DF).
Dengel, P. & Fernholz, H. H. 1990 An experimental investigation of an incompressible turbulent boundary layer in the vicinity of separation. J. Fluid Mech. 212, 615–636.Google Scholar
Driver, D. M. 1991 Reynolds shear stress measurements in a separated boundary layer flow. AIAA Paper 91-1787.
Durbin, P. A. & Belcher, S. E. 1992 Scaling of adverse-pressure-gradient turbulent boundary layers. J. Fluid Mech. 238, 699–722.Google Scholar
Fernholz, H. H. 1993 Near-wall phenomena in turbulent separated flows. Acta Mechanica [suppl.] 4, 1–8.Google Scholar
Goldberg, P. 1966 Upstream history and apparent stress in turbulent boundary layers. MIT Gas Turbine Rep. 85.Google Scholar
Jaroch, M. 1985 Development and testing of pulsed-wire probes for measuring fluctuating quantities in highly turbulent flows. Exps. Fluids 3, 315–322.Google Scholar
Johansson, A. V. & Alfredsson, P. H. 1982 On the structure of turbulent channel flow. J. Fluid Mech. 122, 295–314.Google Scholar
Kline, S. J., Bardina, J. G. & Strawn, R. C. 1983 Correlation of the detachment of two-dimensional turbulent boundary layers. AIAA J. 21, 68–73.Google Scholar
Melnik, R. E. 1989 An asymptotic theory of turbulent separation. Computers Fluids 17, 165–184.Google Scholar
Melnik, R. E. 1991 Some applications of asymptotic theory to turbulent flow. AIAA Paper 91-0220.
Menter, F. R. 1992 Performance of popular turbulence models for attached and separated adverse pressure gradient flows. AIAA J. 30, 2066–2072.Google Scholar
Moses, H. L. 1964 The behaviour of turbulent boundary layers in adverse pressure gradients. PhD dissertation; MIT Gas Turbine Rep. 73.
Naguib, A. M. & Wark, C. E. 1992 An investigation of wall-layer dynamics using a combined temporal filtering and correlation technique. J. Fluid Mech. 243, 541–560.Google Scholar
Perry, A. E. & Schofield, W. H. 1973 Mean velocity and shear stress distributions in turbulent boundary layers. Phys. Fluids 16, 2068–2074.Google Scholar
Robinson, S. K. 1991a Coherent Motions In The Turbulent Boundary Layer. Ann. Rev. Fluid Mech. 23, 601–639.Google Scholar
Robinson, S. K. 1991b The kinematics of turbulent boundary layer structure. NASA-TM 103859.
Ruderich, R. & Fernholz, H. H. 1986 An experimental investigation of a turbulent shear flow with separation, reverse flow, and reattachment. J. Fluid Mech. 163, 283–322.Google Scholar
Schlichting, H. 1979 Boundary Layer Theory. McGraw-Hill.
Schalau, B. Dengel, P. & Thiele, F. 1989 Computation of turbulent boundary-layer flow with separation - a critical evaluation of parameters influencing the results. In Advances in Turbulence 2 (ed. H. H. Fernholz & H. E. Fiedler), pp. 432–437. Springer.
Schofield, W. H. 1981 Equilibrium boundary layers in moderate to strong adverse pressure gradient. J. Fluid Mech. 113, 91–122.Google Scholar
Schofield, W. H. 1986 Two-dimensional separating turbulent boundary layers. AIAA J. 24, 1611–1620.Google Scholar
Shiloh, K., Shivaprasad, B. G. & Simpson, R. L. 1981 The structure of a separating turbulent boundary layer. Part 3. Transverse velocity measurements. J. Fluid Mech. 113, 75–90.Google Scholar
Simpson, R. L., Chew, Y.-T. & Shivaprasad, B. G. 1981O The Structure Of A Separating Turbulent Boundary Layer. Part 1. Mean Flow And Reynolds Stresses. J. Fluid Mech. 113, 23–51.
Simpson, R. L., Chew, Y.-T. & Shivaprasad, B. G. 1981T The Structure Of A Separating Turbulent Boundary Layer. Part 2. Higher-Order Turbulence Results. J. Fluid Mech. 113, 53–73.Google Scholar
Smits, A. J. & Wood, D. H. 1985 The response of turbulent boundary layers to sudden perturbations. Ann. Rev. Fluid Mech. 17, 321–358.Google Scholar
Spangenberg, W. G., Rowland, W. R. & Mease, N. R. 1967 Measurements in a turbulent boundary layer maintained in a nearly separation condition. In Fluid Mechanics of Internal Flow (ed. G. Sovran), pp. 110–151. Elsevier.
Stratford, B. S. 1959a The prediction of separation of the turbulent boundary layer. J. Fluid Mech. 5, 1–16.Google Scholar
Stratford, B. S. 1959b An experimental flow with zero skin friction throughout its region of pressure rise. J. Fluid Mech. 5, 17–35.Google Scholar
Thomas, N. H. & Hancock, P. E. 1977 Grid turbulence near a moving wall. J. Fluid Mech. 82, 481–496.Google Scholar
Townsend, A. A. 1961 Equilibrium layers and wall turbulence. J. Fluid Mech. 11, 97–120.Google Scholar
Wagner, P. M. 1986 Entwicklung eines verbesserten Pulsdrahtanemometers zur Erfassung von Geschwindigkeiten und Korrelationen in turbulenten StrÖmungen (The development of an improved pulsed-wire anemometer to measure speeds and correlations in turbulent flows). Diplomarbeit (thesis), Technische Universitat, Berlin, Germany.