Semi-Empirical Noise Models for Forced Mixer Jet Noise Predictions

Abstract

In recent years there has been a significant interest in the development of jet noise prediction models due to increased restrictions on aircraft noise near airports. However, currently there are no industry tools that can be used to predict the noise from the complex flows of modern jet engines that include internal forced mixers. The four-source method is a noise prediction tool applicable to simple coplanar, coaxial jets. In this study the fundamental components of the four-source model are used as the building blocks for a noise prediction method which would be applicable to coaxial jets with internal forced mixers. First, the four-source model is applied to an internally mixed jet with a confluent or axisymmetric mixer. Then, a two-source noise model is proposed to predict the noise for cases with an internal forced mixer. Three variable parameters in this two-source model are optimized to match the forced mixer experimental noise data. It is shown that the two-source noise model is capable of accurately modeling the noise spectra of internally mixed jets with forced mixers.