A generalized sound extrapolation method for turbulent flows: Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

S. Zhong, X. Zhang

Research output: Unpublished conference presentation (presented paper, abstract, poster)Conference presentation (not published in journal/proceeding/book)Academic researchpeer-review

Abstract

Sound extrapolation methods are often used to compute acoustic far-field directivities using nearfield flow data in aeroacoustics applications. The results may be erroneous if the volume integrals are neglected (to save computational cost), while non-acoustic fluctuations are collected on the integration surfaces. In this work, we develop a new sound extrapolation method based on an acoustic analogy using Taylor’s hypothesis (Taylor 1938 Proc. R. Soc. Lon. A 164, 476–490. (doi:10.1098/rspa.1938.0032)). Typically, a convection operator is used to filter out the acoustically inefficient components in the turbulent flows, and an acoustics dominant indirect variable Dcp is solved. The sound pressure p at the far field is computed from Dcp based on the asymptotic properties of the Green’s function. Validations results for benchmark problems with well-defined sources match well with the exact solutions. For aeroacoustics applications: the sound predictions by the aerofoil–gust interaction are close to those by an earlier method specially developed to remove the effect of vortical fluctuations (Zhong & Zhang 2017 J. Fluid Mech. 820, 424–450. (doi:10.1017/jfm.2017.219)); for the case of vortex shedding noise from a cylinder, the off-body predictions by the proposed method match well with the on-body Ffowcs-Williams and Hawkings result; different integration surfaces yield close predictions (of both spectra and far-field directivities) for a co-flowing jet case using an established direct numerical simulation database. The results suggest that the method may be a potential candidate for sound projection in aeroacoustics applications. ©2018 The Author(s) Published by the Royal Society. All rights reserved.
Original languageEnglish
DOIs
Publication statusPublished - 2018

Keywords

  • Acoustic emissions
  • Acoustic properties
  • Acoustic waves
  • Acoustics
  • Aeroacoustics
  • Computational aeroacoustics
  • Extrapolation
  • Fighter aircraft
  • Forecasting
  • Numerical methods
  • Turbulent flow
  • Vortex flow
  • Vortex shedding
  • Acoustic analogy
  • Acoustic fluctuations
  • Aeroacoustics applications
  • Asymptotic properties
  • Extrapolation methods
  • Integration surfaces
  • Jet noise
  • Vortex shedding noise
  • Acoustic noise
  • Aerofoil noise
  • Wave extrapolation

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