Hostname: page-component-cd9895bd7-lnqnp Total loading time: 0 Render date: 2024-12-28T06:38:36.014Z Has data issue: false hasContentIssue false
  • English
  • Français

The forced mixing layer between parallel streams

Published online by Cambridge University Press:  20 April 2006

D. Oster  and
I. Wygnanski
D. Oster
Affiliation:
School of Engineering, Tel-Aviv University, Ramat-Aviv. Tel-Aviv. Israel Present address: Department of Aerospace Engineering, University of Southern California, Los Angeles, California 90007.
I. Wygnanski
Affiliation:
School of Engineering, Tel-Aviv University, Ramat-Aviv. Tel-Aviv. Israel
Get access Rights & Permissions [Opens in a new window]

Abstract

The effect of periodic two-dimensional excitation on the development of a turbulent mixing region was studied experimentally. Controlled oscillations of variable ampli- tude and frequency were applied at the initiation of mixing between two parallel air streams. The frequency of forcing was at least an order of magnitude lower than the initial instability frequency of the flow in order to test its effect far downstream. The effect of the velocity difference between the streams was also investigated in this experiment. A typical Reynolds number based on the velocity difference and the momentum thickness of the shear layer was l04.

It was determined that the spreading rate of the mixing layer is sensitive to periodic surging even if the latter is so small that it does not contribute to the initial energy of the fluctuations. Oscillations at very small amplitudes tend to increase the spreading rate of the flow by enhancing the amalgamation of neighbouring eddies, but at higher amplitudes the flow resonates with the imposed oscillation. The resonance region can extend over a significant fraction of the test section depending on the Strouhal number and a dimensionless velocity-difference parameter. The flow in the resonance region consists of a single array of large, quasi-two-dimensional vortex lumps, which do not interact with one another. The exponential shape of the mean-velocity distribution is not affected in this region, but the spreading rate of the flow with increasing distance downstream is inhibited. The Reynolds stress in this region changes sign, indicating that energy is extracted from the turbulence to the mean motion; the intensity of the spanwise fluctuations is also reduced, suggesting that the flow tends to become more two-dimensional.

Amalgamation of large coherent eddies is resumed beyond the resonance region, but the flow is not universally similar. There are many indications suggesting that the large eddies in the turbulent mixing layer at fairly large Re are governed by an inviscid instability.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 123 , October 1982 , pp. 91 - 130
Copyright
© 1982 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

Ashurst, W. T. 1977 Sandia Lab. Rep. SNAD 77–8613.
Batt, R. G. 1975 A.I.A.A. 13, 245.
Birch, S. F. 1977 In Turbulence in Internal Flows (ed. S. N. B. Murthy). p. 89. Hemisphere.
Birch, S. F. 1980 In Proc. Stanford Conf. on Complex Turbulent Flows.
Browand, F. K. 1980 Bull. Am. Phys. Soc. 25, 1102.
Browand, F. K. & Latigo, B. O. 1979 Phys. Fluids 22, 1011.
Brown, G. L. & Roshko, A. 1971 Turbulent shear flows. AGARD-CP-93. 23–1.
Brown, G. L. & Roshko, A. 1974 J. Fluid Mech. 64, 775.
Champagne, F. H., Pao, Y. H. & Wygnanski, I. J. 1976 J. Fluid Mech. 74, 209.
Chandrsuda, C., Mehta, R. D., Weir, A. D. & Bradshaw, P. 1978 J. Fluid Mech. 85, 693.
Crighton, D. D. 1975 Prog. Aero. Sci. 16, 31.
Crow, S. C. & Champagne, F. H. 1971 J. Fluid Mech. 48, 547.
Delcourt, B. A. G. & Brown, G. L. 1979 In Proc. 2nd Symp. on Turbulent Shear Flows, London.
Dimotakis, P. E. & Brown, G. L. 1976 J. Fluid Mech. 78, 535.
Dziomba, B. 1981 Ph.D. thesis D83, Technical University Berlin.
Ffowcs Williams, J. E. & Kempton, A. J. 1978 In Structure and Mechanisms of Turbulence II (ed. H. Fiedler). Lecture Notes in Physics, vol. 76, p. 265. Springer.
Fiedler, H. E. 1980 In Proc. Int. Conf. on Turbulent Flows, Madrid.
Fiedler, H. & Thies, H. J. 1978 In Structure and Mechanisms in Turbulence I (ed. H. Fiedler). Lecture Notes in Physics vol. 75, p. 108, Springer.
Foss, J. F. 1977 In Proc. 1st Int. Symp. on Turbulent Shear Flows, Penn. State University.
Goldstein, S. 1930 Proc. Camb. Phil. Soc. 26, 1.
Hernan, M. A. & Jimenez, J. 1979 In Proc. 2nd Symp. on Turbulent Shear Flows, London.
Hill, J. C. 1976 Ann. Rev. Fluid Mech. 8, 135.
Ho, C. M. & Nosseir, N. S. 1978 Bull. Am. Phys. Soc. 23, 1007.
Ho, C. M. & Nosseir, N. S. 1981 J. Fluid Mech. 105, 119.
Hussain, A. K. M. F. & Zedan, M. F. 1978a Phys. Fluids 21, 1100.
Hussain, A. K. M. F. & Zedan, M. F. 1978b Phys. Fluids 21, 1475.
Kelly, R. E. 1967 J. Fluid Mech. 27, 657.
Kibens, V. 1980 A.I.A.A. 18, 434.
Knight, D. 1979 In Proc. 6th Biennial Symp. on Turbulence, University of Missouri–Rolla.
Laufer, J. & Monkewitz, P. 1980 A.I.A.A. Preprint no. 80–0962.
Liepmann, H. W. & Laufer, J. 1947 NACA Tech. Note no. 1257.
Liu, J. T. C., Alper, A. & Mankbudi, R. 1978 In Structure and Mechanisms in Turbulence II (ed. H. Fiedler). Lecture Notes in Physics, vol. 76, p. 202, Springer.
Moore, C. J. 1978 In Structure and Mechanisms of Turbulence II (ed. H. Fiedler). Lecture Notes in Physics, vol. 76, p. 254. Springer.
Michalke, A. 1964 J. Fluid Mech. 19, 543.
Michalke, A. 1965 J. Fluid Mech. 22, 371.
Michalke, A. 1972 Prog. in Aero Sci 13, 213.
Oster, D., Wygnanski, I. & Fiedler, H. 1977 In Turbulence in Internal Flows (ed. S. N. B. Murthy), p. 67. Hemisphere.
Oster, D., Wygnanski, I., Dziomba, B. & Fiedler, H. 1978 In Structure and Mechanisms of Turbulence I (ed. H. Fiedler). Lecture Notes in Physics, vol. 75, p. 48. Springer.
Patel, R. P. 1973 A.I.A.A. J. 11, 67.
Patnaik, P. C., Sherman, F. S. & Corcos, G. M. 1976 J. Fluid Mech. 73, 215.
Pui, N. K. & Gartshore, I. 1979 J. Fluid Mech. 91, 111.
Reichardt, H. 1951 VDI-Forschungsheft 414, 2nd edn [1st edn 1942].
Riley, J. J. & Metcalfe, R. W. 1980 A.I.A.A. Paper no. 80–0274.
Spencer, B. W. 1970 Statistical investigation of turbulent velocity and pressure fields in a two stream mixing layer. Ph.D. thesis, Nuclear Engng Program, Univ. of Illinois. Urbana.
Spencer, B. W. & Jones, B. J. 1971 A.I.A.A. Paper no. 71–613.
Townsend, A. A. 1976 The Structure of Turbulent Shear Flows, 2nd edn. Cambridge University Press.
Yule, A. J. 1971 A.R.C. R&M 3683.
Winant, C. D. & Browand, F. K. 1974 J. Fluid Mech. 63, 237.
Wygnanski, I. 1978 In Proc. Dynamic Flow Conference, Marseille.
Wygnanski, I. J. & Fiedler, H. E. 1970 J. Fluid Mech. 41, 327.
Wygnanski, I., Oster, D. & Fiedler, H. 1979 In Proc. 2nd Symp. on Turbulent Shear Flows, London.
Wygnanski, I., Oster, D., Fiedler, H. & Dziomba, B. 1979 J. Fluid Mech. 93, 325.
Zaman, K. B. M. Q. & Hussain, A. K. M. F. 1980 J. Fluid Mech. 101, 449.
Zaman, K. B. M. Q. & Hussain, A. K. M. F. 1981 J. Fluid Mech. 103, 133.