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Inverted-profile coaxial jet flows relevant to Astovl applications

Published online by Cambridge University Press:  04 July 2016

K. Knowles
Affiliation:
Aeromechanical Systems GroupCranfield University, RMCS Shrivenham, Swindon, UK
L. Kirkham
Affiliation:
Aeromechanical Systems GroupCranfield University, RMCS Shrivenham, Swindon, UK

Abstract

An experimental investigation has been performed into the free jet and wall jet characteristics of high pressure ratio coaxial jets operating with inverted velocity profiles and impinging onto a ground plane. Pitot-static probes have been used to record free jet properties at various distances from the jet exit plane, and wall jet properties of the impinging jets at various radial positions. Jet properties such as velocity decay and spreading rates were calculated and compared to published literature. Wall jet development was investigated and recorded. Inner and outer nozzle pressure ratio (NPR) were altered to give a range of jet exit conditions. The results obtained showed variations in the wall jet properties as jet exit conditions were altered, but wall jet self-similarity was found and varying either nozzle height above the ground plane or NPR did not alter this. Free jet data showed large variations in behaviour with changes in NPR. The inverted profile jets behaved similarly to annular jets, showing similar characteristics. Inner jet pressurisation was observed for inverted profile jets and also significant acceleration of the flow from the inner, lower NPR, jet when this was subcritical.

Type
Research Article
Copyright
Copyright © Royal Aeronautical Society 1998 

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