Laminar-flow design for a Mach-6 quiet-flow wind tunnel nozzle

A high Reynolds-number Mach-6 wind-tunnel nozzle has been designed for a ne w quiet-flow Ludwieg tube. The quiet-flow nozzle is designed to maintain la minar boundary layers on the nozzle walls as far downstream as possible. Tr ansition onset is estimated using the e(N) method. A very long nozzle with gentle curvature is used to reduce Gortler instability. Early transition wo uld occur in adiabatic nozzles of this type, due to the first-mode TS insta bility, The first mode is controlled with an isothermal wall temperature th at is high near the throat and tapers to ambient near the exit. The crossfl ow instability is eliminated through use of an axisymmetric nozzle. The e(N ) method predicts that a quiet-flow Reynolds number in excess of 13 million can be achieved in a prototype nozzle that is 2.61 m (103 inch) long and 0 .23 m (9 inch) in diameter, at 10 atm, (1.03 x 10(6) Pa) total pressure. Th is performance would be about twice that of the existing Langley Mach-6 qui et-now nozzle, At the same pressure, a nozzle that is 10 m (33 ft) long and 0.61 m (24 in.) in diameter is predicted to have a quiet Reynolds number o f more than 36 million, a value sufficient to allow reproducing many flight experiments.