[en] This thesis addresses a vibroacoustic problem in a coupled system consisting of a fluid domain, a poroelastic domain, and a thin elastic solid, such as a flexible plate, through a numerical and experimental method. The understanding of acoustic wave propagation in this coupled problem and the search for mathematical models to simulate and predict the attenuation introduced by porous materials in industrial case studies were proposed within the mechanical engineering research group at the technological centre IKERLAN. To achieve this, a literature review is first conducted on poroelastic materials to understand the parameters they depend on, how they are measured and experimentally characterized, and the study of the different existing mathematical models to simulate wave propagation through these materials. Subsequently, the coupled problem is modeled by developing a finite element numerical code applied to the specific case study of a hexahedral cavity with rigid walls except for the upper wall, which is formed by a thin flexible aluminium plate screwed to the cavity and covered with a layer of poroelastic material. Different models for poroelastic material modeling are compared, ranging from empirical models and phenomenological models of equivalent fluid to models that take into account both the fluid and solid phases of the material. The pressure in the fluid domain is discretized with continuous Q1-Lagrange elements, the plate is discretized by combining standard Q1-Lagrange elements for membrane displacements with MITC4 elements for bending displacements. The poroelastic domain is modeled in each case through its characteristic impedance (considering rigid or movil wall impedance) in empirical models, discretized as the fluid but with density and compressibility modulus with dissipative parts in the equivalent fluid models, and discretized through displacement-displacement degrees of freedom using (Q1)3-Lagrange elements when both solid and fluid phases are modeled. Experimental work is carried out, both for the characterisation of material properties (porous materials and plate) and the sound source excitation, and an experimental validation of the problem is performed by comparing the different models.

[gl] Esta tese aborda a traves dun metodo numerico e experimental un problema vibroacustico nun sistema acoplado comprendido dun dominio de fluido, un dominio poroelastico e un solido elastico fino como e unha placa flexible. A comprension da propagacion de ondas acusticas nese problema acoplado e a busca de modelos matematicos para simular e prever a atenuacion que introducen os materiais porosos en casos de estudo industriais foi exposto dentro do grupo de investigacion de enxenaria mecanica do centro tecnoloxico IKERLAN. Para iso, primeiro levase a cabo unha revision bibliografica sobre os materiais poroelasticos, para conecer os parametros de que dependen, como se miden e caracterizanse experimentalmente, e o estudo dos diferentes modelos matematicos existentes para simular a propagacion de ondas a traves dos devanditos materiais. Posteriormente, modela o problema acoplado desenvolvendo un codigo numerico por elementos finitos aplicado ao caso de estudo concreto dunha cavidade hexaedrica de paredes rixidas salvo a parede superior formada por unha placa fina flexible de aluminio aparafusada a cavidade e recuberta dunha capa de material poroelastico. Comparanse diferentes modelos para a modelizacion do material poroso, desde modelos empiricos e modelos fenomenoloxicos de fluido equivalente, ata modelos que tenen en conta as duas fases, fluida e solida, do material. A presion do dominio de fluido se discretiza con elementos de Lagrange Q1, a placa se discretiza combinando elementos de Lagrange Q1 para os desprazamentos de membrana con elementos MITC4 para os desprazamentos de flexion. O dominio poroelastico se modela en cada caso a traves do seu impedancia caracteristica (considerando impedancia de parede rixida ou mobil) nos modelos empiricos, discretizado como o fluido pero con densidade e modulo de compresibilidad con partes disipativas nos modelos de fluido equivalente, e discretizando a traves de graos de liberdade de desprazamento-desprazamento con elementos de Lagrange (Q1)3 cando se modelan as duas fases, solida e fluida, de que se componen. Levase a cabo un traballo experimental, tanto para a caracterizacion das propiedades dos materiais (porosos e placa) como a fonte sonora de excitacion, e unha validacion experimental do problema comparando os diferentes modelos.