An Nd:glass laser pulse (18 ns, 1.38 J) is focused in a tiny area of about 100-¹m diam under ambient conditions to produce micro-shock waves. The laser is focused above a planar surface with a typical standoff distance of about 4 mm. The laser energy is focused inside a supersonic circular jet of carbon dioxide gas produced by a nozzle with internal diameter of 2.9 mm and external diameter of 8 mm. Nominal value of the Mach number of the jet is around 2 with the corresponding pressure ratio of 7.5 (stagnation pressure/static pressure at the exit of the nozzle). The interaction process of the micro-shock wave generated inside the supersonic jet with the plane wall is investigated using double-pulse holographic interferometry. A strong surface vortex eld with subsequent generation of a side jet propagating outward along the plane wall is observed. The interaction of the micro-shock wave with the cellular structure of the supersonic jet does not seem to in uence the near surface features of the ow eld. The development of the coherent structures near the nozzle exit due to the upstream propagation of pressure waves seems to be affected by the outward propagating micro-shock wave. Mach re ection is observed when the micro-shock wave interacts with the plane wall at a standoff distance of 4 mm. The Mach stem is slightly de ected, indicating strong boundary-layer and viscous effects near the wall. The interaction process is also simulated numerically using an axisymmetric transient laminar Navier-Stokes solver. Qualitative agreement between experimental and numerical results is good.
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