Hostname: page-component-cd9895bd7-jkksz Total loading time: 0 Render date: 2024-12-20T06:23:30.089Z Has data issue: false hasContentIssue false
  • English
  • Français

Experiments on transitional boundary layers with wake-induced unsteadiness

Published online by Cambridge University Press:  26 April 2006

X. Liu  and
W. Rodi
X. Liu
Affiliation:
Institute for Hydromechanics, University of Karlsruhe, 7500 Karlsruhe. Germany Present address: Pratt & Whitney Canada, Mississauga, Ontario, Canada.
W. Rodi
Affiliation:
Institute for Hydromechanics, University of Karlsruhe, 7500 Karlsruhe. Germany
Get access Rights & Permissions [Opens in a new window]

Abstract

Hot-wire measurements were carried out in boundary layers developing along a flat plate over which wakes passed periodically. The wakes were generated by cylinders moving on a squirrel cage in front of the plate leading edge. The flow situation studied is an idealization of that occurring on turbomachinery blades where unsteady wakes are generated by the preceding row of blades. The influence of wake-passing frequency on the boundary-layer development and in particular on the transition processes was examined. The hot-wire signals were processed to yield ensemble-average values and the fluctuations could be separated into periodic and stochastic turbulent components. Hot-wire traces are reported as well as time variations of periodic and ensemble-averaged turbulent fluctuations and of the boundary-layer integral parameters, yielding a detailed picture of the flow development. The Reynolds number was relatively low so that in the limiting case of a boundary layer undisturbed by wakes this remained laminar over the full length of the test plate. When wakes passed over the plate, the boundary layer was found to be turbulent quite early underneath the free-stream disturbances due to the wakes, while it remained initially laminar underneath the undisturbed free-stream regions in between. The turbulent boundary-layer stripes underneath the disturbed free stream travel downstream and grow together so that the embedded laminar regions disappear and the boundary layer becomes fully turbulent. The streamwise location where this happens moves upstream with increasing wake-passing frequency, and a clear correlation could be determined in the experiments. The results are also reported in a mean Lagrangian frame by following fluid parcels underneath the disturbed and undisturbed free stream, respectively, as they travel downstream.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 231 , October 1991 , pp. 229 - 256
Copyright
© 1991 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

Abu Hannam, B. J. & Shaw, R. 1980 Natural transition of boundary layers - the effects of turbulence, pressure gradient, and flow history. J. Mech. Engng Sci. 22, 213–228.Google Scholar
Addison, J. S. & Hodson, H. P. 1989a Unsteady transition in an axial flow turbine. Part 1 -Measurements on the turbine rotor. ASME Paper 89-GT-299.Google Scholar
Addison, J. S. & Hodson, H. P. 1989b Unsteady transition in an axial flow turbine, Part 2-Cascade measurements and modelling. ASME Paper 89-GT-290.Google Scholar
Ashworth, D. A., Lagraff, J. E. & Schultz, D. L. 1989 Unsteady interaction effects on a transitional turbine blade boundary layer. J. Turbomachinery 111, 162–168.Google Scholar
Brembati, F. 1975 An investigation of unsteady turbulent boundary layers. Project Rep. 1975–17. Von Kármán Institute of Fluid Dynamics, Rhode Saint Genese, Belgium.Google Scholar
Carr, W. 1981 A review of unsteady turbulent boundary layer experiments. In Proc. IUTAM Symp. on Unsteady Turbulent Shear Flows (ed. R. Michel), p. 3. Springer.
Cousteix, J. & Houdeville, R. 1988 Effects of unsteadiness on turbulent boundary layers. VKI Lecture Series, 1988–07. 0
Dong, Y. & Cumpsty, N. A. 1989 Compressor blade boundary layers: Part 1 - Test facility and measurements with no incident wakes. ASME Paper 89-GT-50.Google Scholar
Bong, Y. & Cumpsty, N. A. 1989b Compressor blade boundary layers: Part 2 - Measurements with incident wakes. ASME Paper 89-GT-51.Google Scholar
Herbst, R. 1980 Entwieklung von Grenzschichten bei instationärer Zuströmung. Ph.D. thesis, Technical University Darmstadt.
Hodson, H. P. 1983 The development of unsteady boundary layers on the rotor of an axial-flow turbine. AGARD CP 351.Google Scholar
Karlsson, S. K. F. 1985 An unsteady turbulent boundary layer. Ph.D. thesis. Johns Hopkins University.
Lagraff, J. E., Ashworth, D. A. & Schultz, D. L. 1988 Measurement and modelling of the gas turbine blade transition process as disturbed by wakes. ASME Paper 88-GT-232.Google Scholar
Liu, X. & Rodi, W. 1989 Measurements of unsteady flow over and heat transfer from a flat plate. ASME Paper 89-0GT-2.Google Scholar
Parikh, P. G., Reynolds, W. C. & Jayaraman, R. 1981 On the behaviour of an unsteady turbulent boundary layer. In Numerical and Physical Aspects of Aerodynamic Flows (ed. T. Cebeci). University of California at Long Beach. Springer.
Pfeil, H. & Schroder, T. 1981 Decay of the wake behind a cylinder crossing rapidly the flow. AIAA-81-0209.Google Scholar
Pfeil, H., Herbst, R. & Schroder, T. 1983 Investigation of the laminar-turbulent transition of boundary layers disturbed by wakes. Trans. ASME A: Engng for Power 105, 130–137.Google Scholar
Raj, R. & Lakshminarayana, B. 1973 Characteristics of the wake behind a cascade of airfoils. J. Fluid Mech. 61, 707–730.Google Scholar
Rodi, W., Liu, X. & Schönung, B. 1989 Transitional boundary layers with wake-induced unsteadiness. Proc. Fourth Symp. on Numerical and Physical Aspects of Aerodynamic Flows, Long Beach, California, USA.
Schroder, H. 1985 Entwieklung des instationären Nachlaufs hinter quer zur Strömungsrichtung bewegten Zylindern und dessen Einfluß auf das Umschlagverhalten von ebenen Grenz-schichten stromabwärts angeordneter Versuchskörper. Ph.D. thesis, Technical University Darmstadt.
Schubauer, G. B. & Klebanoff, P. S. 1955 Contributions on the mechanics of boundary layer transition. NACA TN 3489.Google Scholar
Spalart, P. R. & Baldwin, B. S. 1989 Direct simulation of a turbulent oscillating boundary layer. In Turbulent Shear Flows VI, pp. 417–440. Springer.
Walker, G. J. 1974 The unsteady nature of boundary layer transition on an axial-flow compressor blade. ASME Paper 74-GT-135.Google Scholar