An oblique shock wave is generated in a Mach 2 flow at a flow deflection angle of 12• . The resulting shock-wave-boundary-layer interaction (SWBLI) at the tunnel wall is observed. A novel traversable shock generator allows the position of the SWBLI to be varied relative to a downstream expansion fan. The relationship between the SWBLI, the expansion fan and the wind tunnel arrangement is studied. Schlieren photography, surface oil flow visualisation, particle image velocimetry and high-spatial-resolution wall pressure measurements are used to investigate the flow. It is observed that stream-normal movement of the shock generator downwards (towards the floor and hence the point of shock reflection) is accompanied by (1) growth in the streamwise extent of the shock-induced boundary layer separation, (2) upstream movement of the shock-induced separation point while the reattachment point remains nearly fixed, (3) an increase in separation shock strength and (4) transition between regular and irregular (Mach) reflection without an increase in incident shock strength. The role of free interaction theory in defining the separation shock angle is considered and shown to be consistent with the present measurements over a short streamwise extent. An SWBLI representation is proposed and reasoned which explains the apparent increase in separation shock strength that occurs without an increase in incident shock strength.

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A focused laser differential interferometer (FLDI) has been experimentally characterized. The static response was probed using a steady, laminar helium jet, and the dynamic response was investigated using a free ultrasonic acoustic beam. In the case of the jet, the refractive index field was independently measured using a Mach-Zehnder interferometer operating simultaneously alongside FLDI. The experimental data were compared with numerical simulations of the FLDI response based on geometric optics and a ray-tracing algorithm. Close quantitative agreement was found between data and simulation results, validating this approach to modeling FLDI performance. Emphasis was given to quantification of the spatial sensitivity of the system, a key characteristic of FLDI, especially when applied to hypersonic ground testing facilities where strong turbulent flow exists outside the core flow.