Characteristics of flow formation in the profiled nozzle of a shock tube

The start-up of the profiled nozzle of a large-diameter (500 mm) shock tube is investigated numerically and experimentally. The nozzle has a geometric expansion ratio of 16 and a minimum cross-section height of 4.34 mm; its developed subsonic section is 44 mm long. The supersonic section, which is 140 mm long, is profiled in such a way as to achieve uniform flow at the exit at Mach 4. The analysis emphasizes the effect of the nozzle geometry. It is shown that the start-up of the profiled nozzle is largely determined by the passage of a secondary shock wave through the test section.