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The structure of a turbulent shear layer bounding a separation region

Published online by Cambridge University Press:  21 April 2006

I. P. Castro  and
A. Haque
I. P. Castro
Affiliation:
Department of Mechanical Engineering, University of Surrey, Guildford, Surrey GU2 5XH, UK
A. Haque
Affiliation:
Department of Mechanical Engineering, University of Surrey, Guildford, Surrey GU2 5XH, UK Present address: Department of Chemical Engineering, Imperial College of Science and Technology, London SW7 2AZ, UK.
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Abstract

Detailed measurements within the separated shear layer behind a flat plate normal to an airflow are reported. A long, central splitter plate in the wake prevented vortex shedding and led to an extensive region of separated flow with mean reattachment some ten plate heights downstream. The Reynolds number based on plate height was in excess of 2 × 1044.

Extensive use of pulsed-wire anemometry allowed measurements of all the Reynolds stresses throughout the flow, along with some velocity autocorrelations and integral timescale data. The latter help to substantiate the results of other workers obtained in separated flows of related geometry, particularly in the identification of a very low-frequency motion with a timescale much longer than that associated with the large eddies in the shear layer. Wall-skin-friction measurements are consistent with the few similar data previously published and indicate that the thin boundary layer developing beneath the separated region has some ‘laminar-like’ features.

The Reynolds-stress measurements demonstrate that the turbulence structure of the separated shear layer differs from that of a plane mixing layer between two streams in a number of ways. In particular, the normal stresses all rise monotonically as reattachment is approached, are always considerably higher than the plane layer values and develop in quite different ways. Flow similarity is not a useful concept. A major conclusion is that any effects of stabilizing streamline curvature are weak compared with the effects of the re-entrainment at the low-velocity edge of the shear layer of turbulent fluid returned around reattachment. It is argued that the general features of the flow are likely to be similar to those that occur in a wide range of complex turbulent flows dominated by a shear layer bounding a large-scale recirculating region.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 179 , June 1987 , pp. 439 - 468
Copyright
© 1987 Cambridge University Press

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References

Adams, E. W., Johnston, J. P. & Eaton, J. K. 1984 Experiments on the structure of a turbulent reattaching shear layer. Rep. MD-43, Thermo-Sciences Div., Dept. Mech. Engng, Stanford University.
Arie, M. & Rouse, H. 1956 Experiments on two-dimensional flow over a normal wall. J. Fluid Mech. 1, 129.Google Scholar
Bradbury, L. J. S. 1976 Measurements with a pulsed wire and hot wire anemometer in the highly turbulent wake of a normal flat plate. J. Fluid Mech. 77, 473.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.Google Scholar
Bradshaw, P. 1967 The effect of initial conditions on the development of a free shear layer. J. Fluid Mech. 26, 255.Google Scholar
Bradshaw, P. & Wong, F. Y. F. 1972 Reattachment of a turbulent shear layer. J. Fluid Mech. 52, 113.Google Scholar
Brederode, V. A. S. L. De 1975 Three-dimensional effects in nominally two-dimensional flows. Ph.D. thesis, Imperial College, University of London.
Castro, I. P. 1973 A highly distorted turbulent free shear layer. Ph.D. thesis, Imperial College, University of London.
Castro, I. P. 1979 Relaxing wakes behind surface-mounted obstacles in rough wall boundary layers. J. Fluid Mech. 93, 631.Google Scholar
Castro, I. P. 1981 Measurements in shear layers separating from surface mounted obstacles. J. Wind. Engng Indust. Aero. 7, 253.Google Scholar
Castro, I. P. 1985 Time domain measurements in separated flows. J. Fluid Mech. 150, 183.Google Scholar
Castro, I. P. 1986 The measurement of Reynolds stresses. In Encyclopedia of Fluid Mechanics, p. 1256, Gulf.
Castro, I. P. & Bradshaw, P. 1976 The turbulence structure of a distorted mixing layer. J. Fluid Mech. 73, 265.Google Scholar
Castro, I. P. & Cheun, B. S. 1982 The measurements of Reynolds stresses with a pulsed wire anemometer. J. Fluid Mech. 118, 41.Google Scholar
Castro, I. P. & Dianat, M. 1983 Surface flow patterns on rectangular bodies in thick boundary layers. J. Wind Engng Indust. Aero. 11, 107.Google Scholar
Castro, I. P., Dianat, M. & Bradbury, L. J. S. 1987 The measurement of fluctuating skin friction with a pulsed wall probe. In Turbulent Shear Flows V (ed. F. Durst, B. E. Launder, F. W. Schmidt & J. H. Whitelaw), p. 278. Springer.
Castro, I. P. & Fackrell, J. E. 1978 A note on two-dimensional fence flows with emphasis on wall constraint. J. Indust. Aero. 3, 1.Google Scholar
Chandrsuda, C. & Bradshaw, P. 1981 Turbulent structure of a reattaching layer. J. Fluid Mech. 110, 171.Google Scholar
Cherry, N. J., Hillier, R. & Latour, M. E. M. P. 1983 The unsteady structure of two-dimensional and reattaching flows. J. Wind Engng Indust. Aero. 11, 95.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.Google Scholar
Devenport, W. J. 1985 Separation bubbles at high Reynolds number: measurement and computation. Ph.D. thesis, University of Cambridge.
Driver, D. M. & Seegmiller, H. L. 1982 Features of a reattaching turbulent shear layer subject to an adverse pressure gradient. AIAA 82–1029.
Eaton, J. K. & Johnston, J. P. 1980 Turbulent flow reattachment: an experimental study of the flow and structure behind a backward facing step. Rep. MD-39, Thermo-Sciences Div., Dept. Mech. Engng, Stanford University.
Eaton, J. K. & Johnston, J. P. 1982 Low frequency unsteadiness of a reattaching turbulent shear layer. In Turbulent Shear Flows, vol. III (ed. L. J. S. Bradbury, F. Durst, B. E. Launder, F. W. Schmidt & J. H. Whitelaw), p. 162. Springer.
Good, M. C. & Joubert, P. N. 1968 Form drag of two-dimensional bluff plates immersed in turbulent boundary layers. J. Fluid Mech. 31, 547.Google Scholar
Green, J. E. 1966 Two-dimensional reattachment as a boundary layer problem. AGARD Conf. Proc. 4.
Jaroch, M. 1985 Development and testing of pulsed wire probes for measuring fluctuating quantities in highly turbulent flows. Exp. Fluids 3, 315.Google Scholar
Kiya, M. & Sasaki, K. 1983 Structure of a turbulent separation bubble. J. Fluid Mech. 137, 83.Google Scholar
Kiya, M. & Sasaki, K. 1985 Structure of large scale vortices and unsteady reverse flow in the reattachment zone of a turbulent separation bubble. J. Fluid Mech. 154, 463.Google Scholar
Kiya, M., Sasaki, K. & Arie, M. 1982 Discrete vortex simulation of a turbulent separation bubble. J. Fluid Mech. 120, 209.Google Scholar
Kline, S. J., Cantwell, B. J. & Lilley, G. M. 1982 The 1980/81 ASOFR-HTTM-Stanford Conference in Complex Turbulent Flows. Thermo-sciences Div., Dept. Mech. Engng, Stanford University.
Mueller, T. J. & Robertson, J. M. 1963 In Modern Developments in Theoretical Applied Mechanics, vol. 1, p. 326.
Patel, V. C. 1965 Calibration of the Preston tube and limitations on its use in pressure gradients. J. Fluid Mech. 23, 185.Google Scholar
Plate, E. 1971 The aerodynamics of shelter belts. Agri. Met. 8, 203.Google Scholar
Pronchick, S. W. & Kline, S. J. 1983 An experimental investigation of the structure of a turbulent reattaching flow behind a backward facing step. Rep. MD-42, Thermo-Sciences Div., Dept. Mech. Engng, Stanford University.
Rodi, W. 1975 A review of experimental data of uniform density free turbulent boundary layers. In Studies in Convection, vol. 1 (ed. B. E. Launder). Academic.
Roshko, A. & Lau, J. C. 1965 Some observations on transition and reattachment of a free shear layer in incompressible flow. In Proc. 1965 Heat Transfer and Fluid Mech. Inst.
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.Google Scholar
Smits, A. J. 1982 Scaling parameters for a time-averaged separation bubble. Trans. ASME I: J. Fluids Engng 104, 178.Google Scholar
Tillman, W. 1945 British Ministry of Aircraft Production, Volkenrode Translation MAP-VG 34–45T.
Tutu, N. K. & Chevray, R. 1975 Crossed-wire anemometry in high intensity turbulence. J. Fluid Mech. 71, 785.Google Scholar
Westphal, R. V., Eaton, J. K. & Johnston, J. P. 1980 A new prove for measurement of velocity and wall shear stress in unsteady, reversing flow. Trans. ASME I: J. Fluids Engng 103, 478.Google Scholar
Westphal, R. V., Eaton, J. K. & Johnston, J. P. 1984 Experimental study of flow reattachment in a single sided sudden expansion. NASA CR-3765.
Wood, D. & Bradshaw, P. 1982 A turbulent mixing layer constrained by a solid surface- Part 1. Measurements before reaching the surface. J. Fluid Mech. 182, 57.Google Scholar