Spatial Stability Analysis of Chevron Jet Profiles

Creators: Gudmundsson, Kristjan; Colonius, Tim

Abstract

We investigate the linear stability characteristics of mean flows produced by round, and chevron nozzles. We derive a Rayleigh equation for the chevron profile, which allows the fast solution of the chevron stability problem. Using PIV and RANS data, we compute the stability characteristics of various chevron/round nozzles. We find there are two main differences between the chevron and round jet: chevron jet growth rates are highly suppressed and peak growth rates shifted to lower frequencies, and phase speeds are somewhat increased. Some preliminary implications on sound generation are discussed. We compare our instability wave results to microphone measurements taken with a phased hydrodynamic array. Our results indicate that the hydrodynamic pressure field of both round, and chevron jets is consistent with that of the instability modes of the turbulent, spreading mean flow.

Additional Information

© 2007 by Kristjan Gudmundsson and Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. The authors acknowledge the support of an AeroAcoustics Research Consortium (AARC) grant from the Ohio Aerospace Institute (OAI). We would like to express great appreciation to Dr. James Bridges and colleagues at the NASA Glenn Research Center for collecting and providing us with their data, and to the Thaerocomp Technical Corp. for performing RANS computations on the SMC001 nozzle. In addition, we would like to thank Dr. Cyrille Breard for pointing out an error in an earlier formulation of Eqn. (2).

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