Analysis of an Acoustic Monopole Source in a Closed Cavity via CUF Finite Elements

Abstract

The noise generated by aircraft is an important issue, which affects the external environment and the passenger’s comfort. The researches about new acoustic solutions often lead to the exploitation of innovative materials, as visco-elastic panels or acoustic metamaterials, in order to rather obtain better acoustic properties than conventional materials, in particular at low frequency. Although, there is a lack of reliable tools able to describe the complex kinematic behaviour of these new materials at low frequency. A new strong formulation, the Carrera Unified Formulation (CUF) based on the Finite Element Method (FEM), enables a wide class of refined shell models, which is able to reproduce the frequency dependent dynamic response of complex multi-layered plates. This formulation, fully developed inside the MUL2 software, is applied to vibro-acoustic analyses too, so the need to integrate new sources and boundary conditions in the software, that are essential to model the acoustic problem. A simple and powerful source is the monopole: a pulsating sphere. This source can be a first try to model the complex sources that affect the noise inside the aircraft, as the engine or the internal sources. Moreover, monopoles are widely used to estimate the transmission loss. Hence, the reason for this work: the creation inside MUL2 of a monopole boundary condition and its validation, comparing the results with those of a well-known FEM based commercial software for vibro-acoustic analyses, Actran.