Optimization of a Mach-6 Quiet Wind-Tunnel Nozzle

Numerical simulations were conducted to optimize the shape and wall-temperature distribution of the Notre Dame Mach 6 quiet tunnel nozzle. The design was optimized by minimizing the overall nozzle length while maintaining sufficiently low disturbance amplification factors and uniform flow at the exit plane. The Boeing Computational Fluid Dynamics flow solver was used to compute laminar-mean-flow solutions for the various geometries and temperature distributions defined by a design of experiments. The Langley Stability and Transition Analysis Code was then used to compute amplification factors for Tollmien–Schlichting waves, second-mode waves, and Görtler vortices. Based on the square root of the sum of the squares of these N-factors, response surfaces were generated that were used to optimize the nozzle design and wall-temperature distribution. Four nozzles with different lengths were developed, and an optimal wall-temperature distribution was determined for each. The total N-factor was found to range from 5.1 to 7.9, with longer nozzles being more stable. All designs reflect an improvement on a baseline design developed in the late 1990s at Purdue University.