Identification of jet noise source using causality method based on large-eddy simulation of a round jet flow

Abstract

An acoustic analogy analysis based on a decomposition of the source term in Lighthill’s equation is discussed in light of a large-eddy simulation of a subsonic turbulent jet exhausting from a baseline round nozzle at Mach number M = 0.9 with Reynolds number Re = 105. The decomposed sub-terms show the nonlinear reciprocal interactions of density, velocity, vorticity, and dilatation fields. To understand the aerodynamic sound generation mechanism, intrinsic links between turbulent flow and emitted acoustic signals are made and applied to the large-eddy simulation data. Cross-correlation functions are used for the links between the far-field sound signals and the sub-terms as well as major flow variables in the jet flow domain. The spatial distributions of cross-correlations are examined to identify the sound source distribution throughout the domain and observe the mutual interactions and cancellations between the decomposed sub-terms. The contributions of sub-terms are also studied in frequency domain.