Instantaneous temperature imaging in hypersonic flows using laser-induced fluorescence of high rotational-quantum-number transitions

This paper investigates the use of one-line laser-induced fluorescence (LIF) thermometry of nitric oxide to study hypersonic flows generated by free-piston shock tunnels. This method has several advantages including lower cost, simpler set up, and reduced errors from optical thickness compared to two-line LIF thermometry. However, comparisons between one-line and two-line fluorescence thermometry indicate that the method is unreliable in air flows. The method is used to provide qualitative temperature maps in the separated flow region forward of a blunt fin attached to a flat plate in a Mach 6.4 freestream.