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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
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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

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