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Instability waves in twin supersonic jets

Published online by Cambridge University Press:  26 April 2006

Philip J. Morris
Philip J. Morris
Affiliation:
Department of Aerospace Engineering, Penn State University, University Park, PA 16802, USA
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Abstract

Calculations are presented for the characteristics of instability waves in the initial mixing region of twin circular supersonic jets. Two models for the basic jet flow are used. In the first, the jets are modelled as two circular vortex sheets. In the second, realistic velocity and density profiles are used. It is shown that the unsteady flow fields of the two jets interact before the time-averaged jets flows have merged. The normal modes or instability waves are classified by their symmetry properties in the twin-jet case and their asymptotic behaviour for large jet separations. Calculations of the growth rates and phase velocities are made for these modes as a function of jet separation and mixing-layer thickness. The associated pressure distributions are also presented. In the realistic jet profile calculations the effect of jet separation is found to be relatively weak. For modes that are even about the symmetry plane between the two jets the pressure levels are found to increase near this plane as the jet separation decreases.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 220 , November 1990 , pp. 293 - 307
Copyright
© 1990 Cambridge University Press

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