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Sonic Flow Through an Abrupt Change in Cross-Section

The steady, transonic flow in a rectangular duct following an abrupt change in section has been studied by measuring the density with a Mach-Zehnder interferometer and velocity with a laser-Doppler velocimeter. The flow structure was controlled either by a single, normal shock wave or by a series of reflected oblique shocks. In the case of the normal shock wave structure the one-dimensional compressible flow theory was found to apply adequately to the overall duct. Within the duct the flow was not one-dimensional, but had a minimum velocity in the centre and four shear layers.