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. In Phase I we will address the practical aspects of making the noise/performance tradeoff for high pressure ratio nozzles. Data will be collected on models in a subscale test facility and evaluated using near field holography and shadowgraph imagery to identify the source characteristics. This will aid development of both CFD and noise prediction algorithms in Phase II.