In-situ temperature, velocity, and density measurements in high-speed flows using burst-mode filtered Rayleigh scattering

Further understanding and characterization of high-speed flow dynamics in transonic to hypersonic regimes is important for the development, testing, and improvement of complex rocket and space vehicles. Laser diagnostics, such as Filtered Rayleigh Scattering (FRS), provide the opportunity to make non-intrusive in situ measurements without the use of physical probes. However, in order to resolve complex dynamics such as boundary layers and shock wave evolution, MHz-rate diagnostics are necessary. The development of the pulsed-burst laser has enabled high energy pulses to be generated at the rates necessary to make measurements and visualizations of these short time-scale phenomena using FRS. While the feasibility of pulse-burst FRS imaging has been previously demonstrated, quantitative measurements of flow properties at MHz-rates are lacking.

In this study, FRS will be extended (i) to higher frame rates up to 1 MHz, (ii) for longer durations up to 100’s of sequential frames, and (iii) with improved capability for multi-parameter measurements. Flow properties such as temperature, velocity, and density will be vital for studying the fundamental phenomena occurring during these flow regimes and for validation of numerical predictions. After validation of the diagnostic approach proposed in this study, extension of the system can be made to study instabilities and flow dynamics in a wide variety of configurations and flow regimes in large-scale test facilities such as at Purdue University and NASA.

This project will further the understanding and characterization of high-speed flow dynamics to improve development and testing of complex space vehicles.

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