Hostname: page-component-78c5997874-xbtfd Total loading time: 0 Render date: 2024-11-09T13:44:08.505Z Has data issue: false hasContentIssue false
  • English
  • Français

Coherence measurements in synthetic turbulent boundary layers

Published online by Cambridge University Press:  20 April 2006

Ömer Savas  and
Donald Coles
Ömer Savas
Affiliation:
School of Aerospace. Mechanical, and Nuclear Engineering, University of Oklahoma, Norman, Oklahoma 73019
Donald Coles
Affiliation:
Graduate Aeronautical Laboratories, California Institute of Technology, Pasadena, California 91125
Get access Rights & Permissions [Opens in a new window]

Abstract

Synthetic turbulent boundary layers were constructed on a flat plate by generating systematic moving patterns of turbulent spots in a laminar flow. The experiments were carried out in a wind tunnel at a Reynolds number based on plate length of 1.7 × 106. Spots were generated periodically in space and time near the leading edge to form a regular hexagonal pattern. The disturbance mechanism was a camshaft that displaced small pins momentarily into the laminar flow at frequencies up to 80 Hz. The main instrumentation was a rake of 24 single hot wires placed across the flow in a line parallel to the surface. The main measured variable was local intermittency; i.e. the probability of observing turbulent flow at a particular point in space and time. The results are reported in numerous (x, z, t)-diagrams showing the evolution of various synthetic flows along the plate. The dimensionless celerity or phase velocity of the large eddies was found to be very nearly 0.88, independent of eddy scale. All patterns with sufficiently small scales eventually showed loss of coherence as they moved downstream. A novel phenomenon called eddy transposition was observed in several flows that contained appreciable laminar regions. The original large eddies were replaced by new eddies at new positions, intermediate to the original ones, while preserving the hexagonal pattern. The present results, together with some empirical properties of a turbulent spot, were used to estimate the best choice of scales for constructing a synthetic boundary layer suitable for detailed study as a model for a natural flow. The values recommended are: spanwise period/thickness ≈ 2.5, streamwise period/thickness ≈ 8.0.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 160 , November 1985 , pp. 421 - 446
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

Badri Narayanan, M. A. & Marvin, J. G. 1978 On the period of the coherent structure in boundary layers at large Reynolds numbers. In Coherent Structure of Turbulent Boundary Layers (ed. C. R. Smith & D. E. Abbott), pp. 380–385. Lehigh University.
Brown, G. L. & Roshko, A. 1974 On density effects and large structure in turbulent mixing layers. J. Fluid Mech. 64, 775–816.Google Scholar
Cantwell, B. J. 1975 A flying hot wire study of the turbulent near wake of a circular cylinder at a Reynolds number of 140,000. Ph.D. Thesis, California Institute of Technology.
Cantwell, B. J. 1981 Organized motion in turbulent flow. Ann. Rev. Fluid Mech. 13, 457–515.Google Scholar
Cantwell, B. & Coles, D. 1983 An experimental study of entrainment and transport in the turbulent near wake of a circular cylinder. J. Fluid Mech. 136, 321–374.Google Scholar
Cantwell, B., Coles, D. & Dimotakis, P. 1978 Structure and entrainment in the plane of symmetry of a turbulent spot. J. Fluid Mech. 87, 641–672.Google Scholar
Chambers, F. W. 1982 Preliminary measurements of a synthetic turbulent boundary layer. Lockheed-Georgia Co., Rep. LG82RR0009.
Chambers, F. W. 1985 Synthetically generated turbulent boundary layer development and structure. AIAA Paper 85–0534.
Chen, C.-H. P. & Blackwelder, R. F. 1978 Large-scale motion in a turbulent boundary layer: a study using temperature contamination. J. Fluid Mech. 89, 1–31.Google Scholar
Coles, D. & Barker, S. J. 1975 Some remarks on a synthetic turbulent boundary layer. In Turbulent Mixing in Nonreactive and Reactive Flows (ed. S. N. B. Murthy), pp. 285–292. Plenum.
Coles, D. & Savaş, ö. 1979 Interactions for regular patterns of turbulent spots in a laminar boundary layer. In Proc. IUTAM Symp. on Laminar-Turbulent Transition, pp. 277–287. Springer-Verlag.
Elder, J. W. 1960 An experimental investigation of turbulent spots and breakdown to turbulence. J. Fluid Mech. 9, 235–246.Google Scholar
Emmons, H. W. 1951 The laminar-turbulent transition in a boundary layer. Part I. J. Aero. Sci. 18, 490–498.Google Scholar
Fleischmann, S. T. & Wallace, J. M. 1984 Mean streamwise spacing of organized structures in transitional and developed bounded turbulent flows. AIAA J. 22, 766–769.Google Scholar
Gad-El-Hak, M., Blackwelder, R. F. & Riley, J. J. 1981 On the growth of turbulent regions in laminar boundary layers. J. Fluid Mech. 110, 73–95.Google Scholar
Goodman, W. L. 1985 Emmons spot forcing for turbulent drag reduction. AIAA J. 23, 155–157.Google Scholar
Haritonidis, J. H., Kaplan, R. E. & Wygnanski, I. 1977 Interaction of a turbulent spot with a turbulent boundary layer. In Structure and Mechanisms of Turbulence I (ed. H. Fiedler), Lecture Notes in Physics No. 75, Springer-Verlag, 234–247.
Hernan, M. A. & Jimenez, J. 1982 Computer analysis of a high-speed film of the plane turbulent mixing layer. J. Fluid Mech. 119, 323–345.Google Scholar
Itsweire, E. C. & Van Atta, C. W. 1984 An experimental investigation of coherent substructures associated with turbulent spots in a laminar boundary layer. J. Fluid Mech. 148, 319–348.Google Scholar
Klebanoff, P. S. 1954 Characteristics of turbulence in a boundary layer with zero pressure gradient. NACA Tech. Note 3178; also NACA Tech. Rep. 1247, 1955.
Kovasznay, L. S. G., Kibens, V. & Blackwelder, R. F. 1970 Large-scale motion in the intermittent region of a turbulent boundary layer. J. Fluid Mech. 41, 283–325.Google Scholar
Matsui, T. 1979 Visualization of turbulent spots in the boundary layer along a flat plate in a water flow. In Proc. IUTAM Symp. on Laminar-Turbulent Transition, pp. 288–296. Springer-Verlag.
Mautner, T. S. & Van Atta, C. W. 1982 An experimental study of the wall-pressure field associated with a turbulent spot in a laminar boundary layer. J. Fluid Mech. 118, 59–77.Google Scholar
Savas, O. 1979a Some measurements in synthetic turbulent boundary layers. Ph.D. Thesis, California Institute of Technology.
Savas, ö. 1979b Some measurements in synthetic turbulent boundary layers. In AGARD CP 271, Turbulent Boundary Layers-Experiments, Theory and Modeling, Paper No. 23.
Schubauer, G. B. & Klebanoff, P. S. 1955 Contributions on the mechanics of boundary-layer transition. NACA Tech. Note 3489; also NACA Tech. Rep. 1289, 1956.
Thomas, A. S. W. & Bull, M. K. 1983 On the role of wall-pressure fluctuations in deterministic motions in the turbulent boundary layer. J. Fluid Mech. 128, 283–322.Google Scholar
Winant, C. D. & Browand, F. K. 1974 Vortex pairing: the mechanism of turbulent mixing-layer growth at moderate Reynolds number. J. Fluid Mech. 63, 237–255.Google Scholar
Wygnanski, I. 1978 On the possible relationship between the transition process and the large coherent structures in turbulent boundary layers. In Coherent Structure of Turbulent Boundary Layers (ed. C. R. Smith & D. E. Abbott), pp. 168–193. Lehigh University.
Wygnanski, I., Haritonidis, J. H. & Kaplan, R. E. 1979 On a Tollmien–Schlichting wave packet produced by a turbulent spot. J. Fluid Mech. 92, 505–528.Google Scholar
Wygnanski, I., Sokolov, M. & Friedman, D. 1976 On a turbulent ‘spot’ in a laminar boundary layer. J. Fluid Mech. 78, 785–819.Google Scholar
Wygnanski, I., Zilberman, M. & Haritonidis, J. H. 1982 On the spreading of a turbulent spot in the absence of a pressure gradient. J. Fluid Mech. 123, 69–90.Google Scholar
Zilberman, M., Wygnanski, I. & Kaplan, R. E. 1977 Transitional boundary layer spot in a fully turbulent environment. Phys. Fluids Suppl. 20, S258–S271.Google Scholar