Laser Diagnostic for Multiple Properties in Unseeded High-Speed Flows

An instrument prototype using an unseeded measurement technique based on filtered Rayleigh scattering (FRS) is proposed for development for simultaneous spatially resolved measurements of density, and velocity components for AEDC transonic and supersonic wind tunnels with the future potential for time-resolved volumetric measurement capability. The method, named two-cell filtered Rayleigh scattering (2C-FRS), involved illuminating the measurement region with a laser sheet and measuring Rayleigh scattered light from the flow with two cameras, each filtered by an iodine vapor cell of a different pressure. The technique was demonstrated on a supersonic coflow jet and was shown to capture the two-dimensional (2D) density and velocity field both spatially and quantitatively. Based on the promising results, we plan to further develop this technique and validate the methodology with measurements of density and multiple velocities in supersonic free jet flows and boundary layers, separated shear layers and off-body flows over test models, laying the groundwork for a validated, deliverable Phase II prototype system. Additional instruments will also be developed to enable time-resolved volumetric measurements in various flow fields.