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 be 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.