Development of planar diagnostics for imaging mach 8 flowfields using carbon dioxide and sodium seeding

In order to investigate the structure of Mach 8 flowfields and the mixing of wall injected fuels, two different diagnostic imaging techniques have been developed. The first uses carbon dioxide enhanced Filtered Rayleigh Scattering (FRS) for imaging the freestream flow and the boundary layer. The second technique uses laser induced fluorescence of sodium seeded into helium as a fuel simulant to provide information on injection and mixing in hypersonic flows. This paper will discuss the development of these diagnostics and their transition into the Mach 8 test facility at the Princeton Gas Dynamics Laboratory. Data are presented from an investigation of a Mach 8 zero pressure gradient boundary layer using the carbon dioxide enhanced FRS technique and from a study of the injection and mixing of sodium seeded helium into the boundary layer to illustrate the importance of these diagnostics to the understanding of the relevant fluid mechanics. An analysis of the boundary layer flow is provided along with an assessment of the implications of perturbing the flowfield using these seeding techniques.