A computational flow-induced noise and time-reversal technique for analysing aeroacoustic sources.

Abstract

A simulation technique to analyse flow-induced noise problems that combines computational fluid dynamics (CFD), the boundary element method (BEM) and an aeroacoustic time-reversal (TR) source localisation method is presented. Hydrodynamic data are obtained from a high-fidelity CFD simulation of flow past a body and aeroacoustic sources are extracted based on Lighthill's acoustic analogy. The incident pressure field on the body due to the aeroacoustic sources is combined with a BEM representation of the body to obtain the spectrum of the direct, scattered and total acoustic pressure fields at far-field microphone locations. The microphone data are then used as input for the time-reversal simulations which are implemented by numerically solving two-dimensional linearized Euler equations. Decomposing the far-field pressure enables the TR simulation of the direct, scattered and total acoustic fields to be performed separately which yields the location and nature of the corresponding aeroacoustic sources. To demonstrate the hybrid CFD-BEM-TR technique, the sound generated by a cylinder in low Mach number cross-flow is considered. The nature of the aeroacoustic sources at the vortex shedding frequency and its second harmonic for the direct, scattered and total fields are identified.