Application of RANS-based method to predict acoustic noise of chevron nozzles

Abstract

Passive noise control devices for jet flows, such as chevron nozzles, have been studied for a long time due to their large application in turbofan engines. The main purpose of their usage is the reduction of low-frequency noise generation and thus decreasing the noise perceived at the far field. This work is a numerical study of acoustic noise generated by jet flow operating at Mach number 0.9 and Reynolds number 1.38×106, considering two chevron nozzle geometries that differ from each other by the penetration angle into the flow. The main aim was to demonstrate that Reynolds averaged Navier Stokes (RANS)-based methods are reliable means to obtain acoustical noise predictions for the industry with a considerably low computational cost. In order to achieve this objective, computational fluid dynamics (CFD) RANS simulations were performed with a cubic k-ɛ model and the acoustic noise spectrum for different angles of radiation was obtained via the Lighthill ray-tracing (LRT) method. The numerical results for the acoustic and flow fields were seen to be in reasonable agreement with the experimental data, suggesting that this methodology can be used as a fast and useful option to predict acoustic noise of jet flows from chevron nozzles.