Investigation of Shock Wave Interaction Using Laser-induced Iodine Fluorescence

Detailed measurements of flow behavior have been taken in a rarefied ‘slip-flow’ regime hypersonic flow (Mach 12) over a sharp edged flat plate with a circular-cylindrical appendage designed to produced shock wave interactions. The flat plate is presented parallel to the wind tunnel freestream to generate a weak shock which impinges on the nearly-normal cylinder bow shock wave. Tests were conducted in a ‘cold’ free jet wind tunnel facility, using nitrogen gas expanded from ambient temperature. Detailed velocity measurements were made from the Doppler shift of the iodine B-X absorption spectra produced by laser-induced fluorescence (LIF) of a trace amount of iodine seeded in the gas. A planar grid of local velocity with a resolution on the order of one mean-free-path in the flow free stream was obtained using a wide sheet-beam from a frequencytunable multiwatt argon laser to excite LIF and a low-noise CCD camera to record multiple images. In addition to the velocity measurements, these spectra provide information on the local translational and rotational temperature in the flow.