Investigation of a Two-Step Nozzle in the Langley 11-Inch Hypersonic Tunnel

Flow surveys have been made in the first of several nozzles to be investigated in the Langley 11-inch hypersonic tunnel. The nozzle was designed by the method of characteristics for a Mach number of 6.98. Two 2-dimensional steps were used: the first step expanded the air in the horizontal plane to a Mach number of 4.36 and the second in the vertical plane to a Mach number of 6.98. The test results showed that, although a maximum Mach number of about 6.5 was obtained, the flow in the test section was not sufficiently uniform for quantitative wind-tunnel test purposes. Deviations from the design flow were traced to the presence of a thick boundary layer which developed in the first step along the parallel walls.