Coupled velocity and temperature acoustic tomography in heated high subsonic Mach number flows

Abstract

The application of acoustic tomography (AT) for simultaneous velocity and static temperature estimation has generally been restricted to low subsonic Mach number applications due to the increased complexities associated with acoustic refraction, high computational resource requirements, and a limited range of practical applications. The current work describes a novel AT method for application in such conditions and presents the results of a proof of concept laboratory jet experiment. Using a traversed set of acoustic sound source and microphones, acoustic propagation time measurements were collected at Mach 0.48 and 0.72 jet conditions (with total temperatures of 675 K) along three azimuthal orientations and used to perform AT. A comparison of intrusive and non-intrusive measurements showed that a three orientation reconstruction could approximate jet plume size and location within 1/4th of the jet’s radius. Several sensitivity studies were conducted to assess the behavior and limitations of the proposed AT method. In particular, the effects of orientation count, reconstruction resolution, and displacement measurement errors were investigated. The findings of these sensitivity studies were used to make recommendations for future experiments. This application is the first time an acoustic method is used to non-intrusively and simultaneously measure jet velocity and static temperature distributions in high subsonic Mach number flows.