Hostname: page-component-78c5997874-m6dg7 Total loading time: 0 Render date: 2024-11-05T03:56:16.414Z Has data issue: false hasContentIssue false
  • English
  • Français

Optical compensation measurements on the unsteady exit condition at a nozzle discharge edge

Published online by Cambridge University Press:  29 March 2006

D. Bechert  and
E. Pfizenmaier
D. Bechert
Affiliation:
DFVLR-Institut für Turbulenzforschung, 1 Berlin 12, Müller-Breslau-Strasse 8
E. Pfizenmaier
Affiliation:
DFVLR-Institut für Turbulenzforschung, 1 Berlin 12, Müller-Breslau-Strasse 8
Get access Rights & Permissions [Opens in a new window]

Abstract

The exit condition at the trailing edge of a nozzle for slightly unsteady flow has been investigated experimentally. This problem plays a crucial role in sound transmission through nozzles with flow. The measuring technique used is new and is based on the synchronization of a laser beam to the wave motion of a small smoke filament in the boundary layer leaving the nozzle. The resolution of the jet flow deflexion measurements is of the order of 1–3μm. The authors found the jet deflexion envelope to have a nearly parabolic shape near the nozzle edge. The size of this ‘parabolic’ region decreases with decreasing Strouhal number. This statement applies to the motion of the exterior border of the boundary layer at the dividing streamline between flow originating from the interior of the nozzle and flow coming from outside. It was found that the unsteady flow problem near the edge remains linear for fluctuating velocities of small magnitude.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 71 , Issue 1 , 9 September 1975 , pp. 123 - 144
Copyright
© 1975 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

Bechert, D. 1971 About some simplifications concerning calculations in aeroacoustics [in German]. D.L.R. Rep. FB 71–25.Google Scholar
Bechert, D. & Michel, U. 1974 The control of a thin free shear layer with and without a semi-infinite plate with a pulsating monopole or dipole. Some new closed form solutions. D.L.R. Rep. FB 74–22.Google Scholar
Bechert, D. & Michel, U. 1975 The control of a thin free shear layer with and without a semi-infinite plate by a pulsating flow field. Acustica, 33 (to appear).Google Scholar
Bechert, D. & Pfizenmaier, E. 1971 On the Kutta condition at the nozzle discharge edge in a weakly unsteady nozzle flow [in German]. D.L.R. Rep. FB 71–09. (Trans. R.A.E. Lib. Trans. no. 1617.)
Bechert, D. & Pfizenmaier, E. 1973 Optical compensation measurements on the unsteady exit condition at a nozzle discharge edge. An investigation in connection with sound transmission through nozzles with flow [in German]. D.L.R. Rep. FB 73–93.
Brown, S. N. & Stewartson, K. 1970 Trailing-edge stall. J. Fluid Mech. 42, 561.Google Scholar
Grighton, D. G. 1972a Radiation properties of the semi-infinite vortex sheet. Proc. Roy. Soc. A 330, 185.Google Scholar
Crighton, D. G. 1972b The excess noise field of subsonic jets. J. Fluid Mech. 56, 683.Google Scholar
Crighton, D. G. & Leppington, F. G. 1974 Radiation properties of the semi-infinite vortex sheet: the initial-value problem. J. Fluid Mech. 64, 393.Google Scholar
Freymuth, P. 1966 On transition in a separated laminar boundary layer. J. Fluid Mech. 25, 683.Google Scholar
Lighthill, M. J. 1952 On sound generated aerodynamically: I. Proc. Roy. Soc. A 211, 564.Google Scholar
Lighthill, M. J. 1954 On sound generated aerodynamically: II. Proc. Roy. Soc. A 22, 1.Google Scholar
Michalke, A. 1962 Theoretical and experimental investigation of an axisymmetrical laminar boundary layer of a nozzle [in German]. Ing. Arch. 31, 268.Google Scholar
Michalke, A. 1965 On spatially growing disturbances in an inviscid shear layer. J. Fluid Mech. 23, 521.Google Scholar
Michalke, A. 1971 Instability of a compressible circular jet with reference to the influence of the free jet boundary layer thickness [in German]. Z. Flugwiss. 19, 319.Google Scholar
Miksad, R. W. 1972 Experiments on the nonlinear stages of free-shear-layer transition. J. Fluid Mech. 56, 695.Google Scholar
Möhring, W. 1975 On flows with vortex sheets and solid plates. J. Sound Vib. 38, 403.Google Scholar
Orszag, S. A. & Crow, S. C. 1970 Instability of a vortex sheet, leaving a semi-infinite plate. Studies of Appl. Math. 49, 167.Google Scholar
Pfizenmaier, E. 1973 On the instability of the sound-influenced free jet [in German]. D.L.R. Rep. FB 73–69. (Trans. Esro TT-122.)