Schemes for the sound transmission of flat, curved and axisymmetric structures excited by aerodynamic and acoustic sources

M. Ichchou,F. Franco,O. Bareille,C. Droz,S. De Rosa,F. Errico

doi:10.1016/j.jsv.2019.05.041

Abstract

The paper describes a methodology for computing the sound transmission loss of any flat, curved and cylindrical, homogeneous and periodic structure, under any type of acoustic and/or aerodynamic load. An approximate excitation model is introduced to reproduce uncorrelated and spatially-correlated loads using a wavenumber integration of surface waves. Then, a wave finite element formulation is developed and interfaced with the excitation models in order to cover industrially-relevant case studies. Analytical, numerical and experimental transmission losses are presented for validation purposes. Finite size effects are also taken into account using a spatial windowing and a cylindrical analogy, for curved structures. Different periodic-cell designs are also compared and investigated under turbulent boundary layer and diffuse acoustic field excitations.

Highlights

Sandwich composite structures are extensively used in modern aerospace industry as well as in the automotive, naval and civil ones because they are lighter and stronger than most advanced panels in aluminium alloys
In analogy to what happens for an infinite flat structure, the internal acoustics is assumed to be composed by single out-going waves and internal acoustic waves’ reflections/transmission are not modelled (see Eq (13))
This work proposes a numerical approach for the estimation of the sound transmission loss of complex flat, curved and cylindrical periodic structures, under any type of acoustic and aerodynamic load

Summary

Introduction

Sandwich composite structures are extensively used in modern aerospace industry as well as in the automotive, naval and civil ones because they are lighter and stronger than most advanced panels in aluminium alloys The anisotropy of such structures can be modified by changing the material and the shape of the core, obtaining different wave propagation properties. These types of structures are known for having poor vibroacoustic performances which, often, can result in higher interior noise levels. This problem has a strong impact in many engineering areas, from space launchers to aircraft fuselages. Some FEM applications for the vibroacoustic analysis of simple structures, under random aeroacoustic loads, are present in literature [1, 2, 3, 4, 5]

Methods

Discussion

Conclusion