A.F.P.: Flow-tagging velocimetry for hypersonic flows using fluorescence of nitric oxide

We demonstrate a new variation of molecular-tagging velocimetry for hypersonic ows based on laser-induced uorescence. A thin line of nitric-oxide molecules is excited with a laser beam and then, after a time delay, a uorescence image of the displaced line is acquired. One component of velocity is determined from the time of ight.Thismethodis appliedtomeasure the velocity pro le in aMach 8.5 laminar, hypersonicboundarylayer in the Australian National University’s T2 free-piston shock tunnel. The single-shot velocity measurement uncertainty in the freestream was found to be 3.5%, based on 90 % con dence. The method is also demonstrated in the separated ow region forward of a blunt n attached to a at plate in a Mach 7.4 ow produced by the Australian National University’s T3 free-piston shock tunnel. The measurement uncertainty in the blunt n experiment is approximately 30%, owing mainly to low uorescence intensities, which could be improved signi cantly in future experiments. This velocimetrymethod is applicable to very high-speed ows that have low collisional quenching of the uorescing species. It is particularly convenient in facilities where planar laser-induced uorescence is already being performed