Flow and Acoustics Characteristics of Chevron Nozzles in Coaxial Jets - LES & Acoustic Analogy Investigation

Abstract

In the last decades there has been significant interest in developing source-based jet noise suppression methods as well as developing jet noise prediction approaches that may involve modified geometry and complex flow fields. In this numerical study the acoustic field generated by flow unsteadiness in a non-isothermal coaxial turbulent jet with and without forced mixers on the core nozzle is determined using a hybrid approach. In the flow solver the Navier-Stokes equations are resolved using Large Eddy Simulation (LES) to model the turbulence. The acoustic solver is based on an inhomogeneous wave equation, where the instantaneous acoustic sources are computed from the LES data. The flow and the acoustic data from the coaxial jet case with chevrons on the core nozzle are compared with those obtained from a baseline coaxial jet, showing the spatial character of the acoustic benefit when forced mixers are used on the core nozzle. The computed results are compared with experimental data performed with the same geometry. The agreement between the two data sets in terms of sound pressure levels (SPLs) and noise directivity is very good.