A Measurement of Disturbance Propagation in High-Speed Flow by a Laser Induced Fluorescence Method(Application to a Supersonic Cavity Flow)

A method for measuring propagation of disturbance in a high-speed flow has been developed by using a laser induced fluorescence (LIF) technique. A cross correlation function between the time-dependent LIF signal and a pressure sensor signal at a reference point enables to measure a propagation speed of disturbance. Through a bandpass filter, the speed of disturbance with a particular frequency can he obtained. A feature of disturbance propagation can be grasped by drawing maps for the cross-correlation coefficients on a space at successive delay-times and making an animation. The method was applied to a supersonic flow over a rectangular cavity with length to depth ratio of 2, to elucidate feedback mechanisms of self sustaining flow oscillation with several dominant frequencies.