Flow quality of hypersonic wind-tunnel nozzles designed using computational fluid dynamics

A new methodology has been demonstrated for designing the aerodynamic contour of hypersonic wind-tunnel nozzles using a computational fluid-dynamics-based design and optimization procedure. The new design method was based on a least-squares parabolized Navier-Stokes design and optimization procedure developed by the first author. An optimization problem was solved using the new design method to determine the aerodynamic contour that minimized the flowfield Mach-number variation. Two existing wind-tunnel nozzles were remachined with the new aerodynamic contours designed with this procedure. The flow quality of the nozzles was examined using detailed pitot-pressure profiles measured in the test section. The flow quality of the remachined nozzles showed an improvement over a recently designed and constructed wind-tunnel nozzle based on the classical method-ofcharacteristics boundary-layer correction technique. However, the flow quality was not as uniform as predicted, because of disturbances emanating from mechanical joints. The pitot-pressure profile away from the disturbance was extremely uniform, significantly better than for previous wind-tunnel nozzles at similar Mach numbers, demonstrating the importance of using a computational-based design procedure for wind-tunnel nozzles that have to operate with thick boundary layers.