Using Linear Stability Analysis as a Tool to Evaluate Jet and Cavity Flow Control Situations

Abstract

Flow control has the potential to improve the efficiency of aerospace systems. The design of a flow control system requires knowledge of flow phenomena including information on the evolution of naturally occurring disturbances in the flow. Natural flow disturbances can evolve at various frequencies and growth rates and can assume various mode shapes. Knowledge of the behavior of natural flow instabilities could aid actuator selection and strategy for flow control. In this paper we use linear stability analysis as a tool to analyze jet and cavity flow control situations. We present results from a linear stability study of the resonant acoustic mechanisms in subsonic impinging jets and subsonic cavity flows using the compressible Rayleigh equation. In an impinging jet, the subsonic instabilities are known to be responsible for the acoustic feedback, which is an essential link in setting up the resonances associated with this flow. The instabilities of the helical type are also relevant from the standpoint o...