Hostname: page-component-cd9895bd7-mkpzs Total loading time: 0 Render date: 2025-01-05T23:48:19.276Z Has data issue: false hasContentIssue false
  • English
  • Français

Effect of initial conditions on two-dimensional free shear layers

Published online by Cambridge University Press:  20 April 2006

B. Dziomba  and
H. E. Fiedler
B. Dziomba
Affiliation:
Hermann-Föttinger-Institut für Thermo- und Fluiddynamik, Technische Universität Berlin Currently at University of British Columbia, Vancouver.
H. E. Fiedler
Affiliation:
Hermann-Föttinger-Institut für Thermo- und Fluiddynamik, Technische Universität Berlin
Get access Rights & Permissions [Opens in a new window]

Abstract

The influence of periodic perturbations on the development of two-dimensional free shear layers generated by a splitter plate was investigated in cases where the ratios of the two velocities u1 and u2 either side of the splitter plate were such that 0 < u1/u2 < 1. Investigations were carried out in both a suction and a blower wind tunnel. Results show that even very weak periodic perturbations caused by the wind tunnel may cause significant nonlinear spreading in the downstream development of the shear layer, a behaviour which is also observed when the shear layer is deliberately excited. Other things being equal, the effect of the disturbance is greater when flow separation at the splitter plate is turbulent than when it is laminar.

No self-induced feedback frequencies were measured in the test section. All tonal components that were detected in the flow could be traced to external sources.

The influence of trailing-edge thickness on the shear-layer development is found to become significant when it exceeds 50% of the sum of boundary-layer displacement thickness at the point of separation. As the trailing edge becomes thicker, the range over which the shear layer is self-similar is shifted farther downstream. This behaviour may be crucial for predicting the evolution of shear layers in high-speed flows having thin boundary layers at separation.

The momentum thickness criterion for estimating the development length of the flow as suggested by Bradshaw is shown to be insufficient for two-stream layers, where additional parameters, e.g. the trailing-edge geometry, have to be taken into account. Discrepancies between previously published observations of shear layers, as well as the considerable scatter in reported measurements, may therefore, to a large extent, be attributable to contamination of the experimental facility.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 152 , March 1985 , pp. 419 - 442
Copyright
© 1985 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.)

References

Abramovich, G. N. 1963 The theory of turbulent jets. MIT Press, Cambridge, Mass.
Batt, R. G. 1975 Some measurements on the effect of tripping the two-dimensional shear layer. AIAA J. 13, 245–247.Google Scholar
Bechert, D. 1982 Excited waves in shear layers. Deutsche Forschungs- und Versuchsanstali für Luft- und Raumfahrt. DFVLR-FB 82–83.
Birch, S. F. 1976 On the developing region of a plane mixing layer. In Proceedings of SQUID-conference. Plenum Press.
Birch, S. F. & Eggers, M. 1972 A critical review of the experimental data for developed free turbulent shear layers. Free turbulent shear flows. NASA SP-321, 11–40.
Bradshaw, P. 1966 The effect of initial conditions on the development of a free shear layer. J. Fluid Mech. 26, 225–236.Google Scholar
Browand, F. K. & Latigo, B. O. 1979 Growth of the two-dimensional mixing layer from a turbulent and non-turbulent boundary layer. Phys. Fluids 22, 1011–1019.Google Scholar
Brown, G. L. & Roshko, A. 1974 On density effects and large structure in turbulent mixing layers. J. Fluid Mech. 64, 775–816.Google Scholar
Crighton, D. G. & Gaster, M. 1976 Stability of slowly diverging jet flow. J. Fluid Mech. 77, 397–413.Google Scholar
Dimotakis, P. E. & Brown, G. L. 1976 The mixing layer at high Reynolds number: large structure dynamics and entrainment. J. Fluid Mech. 78, 535–60.Google Scholar
Drubka, R. E. & Nagib, H. M. 1981 Instabilities in the near field of turbulent jets and their dependence on initial conditions and Reynolds number. AFOSR Scientific Report IIT Fluids and Heat Transfer Rep. R. 81–2.Google Scholar
Dziomba, B. 1981 Experimentelle Untersuchung zum Einfluß von Anfangs-und Randbedingungen auf die Ausbreitung einer freien zwei-dimensionalen Scherschicht. Dissertation Tu Berlin.
Fiedler, H. E. & Mensing, P. 1985 The plane turbulent shear layer with periodic excitation. Submitted for publication in J. Fluid Mech.Google Scholar
Fiedler, H. & Thies, H. J. 1978 Some observations in a large two-dimensional shear layer. In Structure and Mechanisms of Turbulence I (ed. H. Fiedler), Lecture Notes in Physics, Vol. 75, pp. 108–117. Springer.
Freymuth, P. 1966 On transition in a separated laminar boundary layer. J. Fluid Mech. 25, 683–704.Google Scholar
Görtler, H. 1942 Berechnung von Aufgaben der freien Turbulenz auf Grund eines neuen Näherungsansatzes. Z. angew. Math. Mech. 22, 244–253.Google Scholar
Hussain, A. K. M. F. & Zedan, M. F. 1978a Effects of the initial condition on the axisymmetric free shear layer: Effects of the initial momentum thickness. Phys. Fluids 21, 1100–1111.Google Scholar
Hussain, A. K. M. F. & Zedan, M. F. 1978b Effects of the initial condition on the axisymmetric free shear layer: Effects on initial fluctuation level. Phys. Fluids 21, 1475–1481.Google Scholar
Kleis, S. J. & Hussain, A. K. M. F. 1979 The asymptotic state of the plane mixing layer. Bull. Am. Phys. Soc. 24, 1132.Google Scholar
Korst, H. H. & Chow, W. L. 1962 Mech. Eng. NT 392–3, Univ. of Illinois, Urbana.
Liepmann, M. W. & Laufer, J. 1947 Investigation of free turbulent mixing. NACA Tech. Note No. 1257.
Mensing, P. 1981 Einfluß kontrollierter Störungen auf eine ebene, turbulente Scherschicht. Dissertation, TU Berlin.
Michalke, A. 1965 On spatially growing disturbances in an inviscid shear layer. J. Fluid Mech. 23, 521–544.Google Scholar
Michalke, A. & Schade, H. 1963 Zur Stabilität von freien Grenzschichten. Ing. Arch. 33, 1.Google Scholar
Miles, J. B. & Shih, J. S. 1968 Similarity parameter for two-stream turbulent jet mixing region. AIAA J. 6, 7.Google Scholar
Oster, D. 1980 The effect of an active disturbance on the development of the two-dimensional turbulent mixing region. Ph.D. Thesis, Tel Aviv University.
Oster, D., Wygnanski, I. J. & Fiedler, H. 1976 Some preliminary observations on the structure of the two-dimensional turbulent mixing layer. In Proceedings of SQUID-Conference. Plenum.
Pui, N. K. & Gartshore, I. S. 1979 Measurements of the growth ratio and structure in plane turbulent mixing layers. J. Fluid Mech. 91, 111–130.Google Scholar
Sabin, C. M. 1963 An analytical and experimental study of the plane, incompressible turbulent free shear layer. US Air Force Report MD-9.
Spencer, B. W. & Jones, B. G. 1971 Statistical investigation of pressure and velocity fields in the turbulent two-stream mixing layer. AIAA Paper 771–613.
Winand, C. D. & Browand, F. K. 1974 Vortex pairing: The mechanism of turbulent mixing layer growth at moderate Reynolds Numbers. J. Fluid Mech. 63, 237–256.Google Scholar
Wygnanski, I., Oster, D. & Fiedler, H. 1979 A forced, plane, turbulent mixing layer; a challenge for the predictor. In Proc. 2nd Symp. on Turbulent Shear Flows, July 2–4, London.
Zaman, K. B. M. Q. & Hussain, A. K. M. F. 1981 Turbulence suppression in free shear flows. J. Fluid Mech. 103, 133–159.Google Scholar