A hydro-acoustic mode decomposition method for velocity and pressure field and application to a subsonic turbulent jet

Abstract

A hydrodynamic and acoustic mode decomposition method for velocity and pressure based on Helmholtz decomposition and momentum equation is proposed. It is able to decompose the flow variables of velocity and pressure into their vortical, acoustic, and entropic components. The method is verified and validated by a Mach 0.9 turbulent jet flow. The spectral properties of the decomposed hydrodynamic and acoustic components verify that the method successfully separates the two parts. Spectral proper orthogonal decomposition analysis of the decomposed fields clearly identifies the spatial structures of the first three radial orders trapped waves in the potential core and validates the shallow angle noise generation mechanism of spectral leakage for subsonic wavepacket. The present work provides insights into flow–acoustic interaction and aeroacoustic source identification for turbulent jets.