Coherent interferometric imaging in a random flow

TL;DR

This paper develops and tests extended imaging algorithms based on Kirchhoff migration and coherent interferometry to localize acoustic sources in turbulent, moving media, accounting for ambient flow effects.

Contribution

It introduces flow-aware modifications of KM and CINT algorithms for acoustic imaging in inhomogeneous moving media, extending their applicability.

Findings

Algorithms successfully localize sources in turbulent jet flows.

Flow modifications improve imaging accuracy in moving media.

Numerical simulations validate the effectiveness of the proposed methods.

Abstract

This paper is concerned with the development of imaging methods to localize sources or reflectors in inhomogeneous moving media with acoustic waves that have travelled through them. A typical example is the localization of broadband acoustic sources in a turbulent jet flow for aeroacoustic applications. The proposed algorithms are extensions of Kirchhoff migration (KM) and coherent interferometry (CINT) which have been considered for smooth and randomly inhomogeneous quiescent media so far. They are constructed starting from the linearized Euler equations for the acoustic perturbations about a stationary ambient flow. A model problem for the propagation of acoustic waves generated by a fixed point source in an ambient flow with constant velocity is addressed. Based on this result imaging functions are proposed to modify the existing KM and CINT functions to account for the ambient flow velocity. They are subsequently tested and compared by numerical simulations in various configurations, including a synthetic turbulent jet representative of the main features encountered in actual jet flows.