Practical Assessment of Noise/Performance Trade for High NPR Nozzles

With improvements in high performance military jet aircraft engines and the increase in complexity of the exhaust systems the noise produced has become problematic. Reducing these noise levels, while maintaining overall system performance, has become the driving issue in new nozzle designs. This proposal will focus on nozzle designs of practical application that can be implemented on current high NPR engine configurations, such as chevrons (or serrations) cut into the trailing edge of the nozzle. Phase I demonstrated that noise measurement can be conducted simultaneously with performance measurement in a thrust stand using a near field microphone array. Phase will focus on demonstrating that the near field acoustic measurement can be extrapolated to the far field using acoustic holography in the forward flight environment. Near field and far field measurements will be conducted simultaneously in high quality jet noise facility to demonstrate that the extrapolation process can provide sufficient detail for design purposes. This will allow future programs to be conducted with confidence with just the near field array in the thrust stand.