The design and operation of a fixed nozzle of axial symmetry for high-subsonic Mach numbers and for a supersonic Mach number of 1.2 was investigated in connection with the conversion of a large high-speed subsonic wind tunnel to transonic operation. The nozzle was carefully designed by potential-flow theory and was adjusted for boundary-layer development. The results of flow surveys in the nozzle indicated that the uniformity of the flow in the supersonic test section was suffi¬cient for model testing. In the subsonic test section provided in the region of the nozzle throat, the flow was of remarkable uniformity and permitted the testing of small models at Mach numbers as great as 0.99.nSmall flow irregularities, which were propagated along Mach lines, tended to become concentrated near the nozzle axis. Reduction of some waviness in the surface of the nozzle by amounts of the order of 0.006 inch resulted in improvement of the flow, and deviations from the design Mach number at the nozzle axis did not then exceed 0.02. Small surface irregularities of the nature of roughness, cracks in the surface of the plaster liner, and small discontinuities in slope produced no noticeable effect on the flow and were presumed masked by the thick boundary layer.
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