Conference_programme: 2.1 - Aeroacoustics
Lecture: Prediction of fine scale jet mixing noise refraction effects using a two-step propagation technique
Author(s): Martelet Yann, Bailly Christophe
Summary:
In order to reduce the noise pollution around airports with an ever-growing air traffic, aircraft needs to respect stricter and stricter noise regulation following the chapter 4 of ICAO. A real challenge has emerged for aircraft manufacturers, in particular the investigation of installation effects induced by new architectures.\n\nNumerous valuable methods have been previously developed, but the request for more accurate predictions and the changes in turbofan-engine geometry have revived the interest in this topic. The aim of this study is to present a methodology based on Tam and Auriault's model for predicting the jet mixing noise induced by fine scale turbulence and the directivity including the refraction through the mixing layer and the presence of a cone of silence near the jet axis. A statistical approach is used to calculate aeroacoustic sources using the turbulence data provided by a RANS CFD computation. The acoustic propagation is obtained by splitting the path of the waves in two parts in the framework of the geometrical acoustic. The first part is through the jet from the sources to the point where the refraction will take place then to the observer. All the equations needed to obtain the triplets (S_i,R_i,M), namely the source point, the location of the refraction and the observer, will be given. Additionally, the formula to perform the two-step propagation will also be written in order to provide the reader with a hands-on methodology.\n\nThe methodology will be assessed on the dual stream EXEJET nozzle (diameter of the secondary nozzle at exhaust d_sec=0.23m). The coaxial jet is isolated. The noise is estimated for high-power takeoff at a Mach number M_jet=0.785 and an external flow of M_ext=0.273.\n\nThe implementation has been carried successfully and has provided preliminary results. Various results will be reported by the submission of the full text.
Corresponding author
Name: Mr Yann Martelet
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Country: France
