ASCENT 59: Aerodynamic Design of Nozzles and Mixers

The FAA ASCENT 59 project brings together academics and industry; verifying the design frameworks that will be needed for supersonic aircraft to meet community noise limits. The most significant challenge is jet noise at takeoff. Risk reduction has begun by building a relevant scale model test article with bypass ratio of about 3.0, indicative of cycles for supersonic aircraft. A comprehensive simulation campaign will be completed, using a hierarchy of methods from simple to complex, to demonstrate that modern tools can predict the measured signatures from testing which will characterize the jet statistics and noise. This paper describes the design of an internally mixed nozzle including initial sizing based on isentropic methods, iterative contour refinements, and CFD validation of performance characteristics to ensure the model is representative of an exhaust system built for industry. Checks are described to ensure avoidance of shockwave induced howling at subcritical operating conditions which were observed in previous testing. Modular components have been designed to enrich the test via variations in mixer topology (one annular and two forced mixers) and four nozzle mixing lengths. Operating maps are provided to ensure that signature results can be normalized to constant thrust and for selecting thermodynamic operating conditions that preserve design intent.