Development of Acoustic Metamaterial for noise mitigation in ducts: scenario, framing and set-up

During recent decades, metamaterials have shown interesting properties in the acoustic, mechanical and aerospace engineering fields. Due to their characteristics of tunability on target bandwidth and the freedom of design for air passage, Acoustic Metamaterial AMMs applications have lately extended into the multi-physical domain. For example, they can be seen as effective solutions in systems that simultaneously allow noise application and fluid passage. Numerical methods such as FEM have been largely validated in order to test single metamaterial physics issues, while mixed physics methods have been exploited in the latest years for research and industrial purposes. However, there is still no precise method to follow when tuning Acoustic. For this reason, in this study, a Multiphysical FEM is evaluated to assess the implications of different flow characteristics on acoustic performance. First, two mono-physical models separately evaluate the fluid dynamic and acoustic problem of a basic application of an airflow velocity field applied at a cylindrical duct. The two physical numerical models are then combined in the second stage, and a correlation between the two approaches is drawn. In this way, a multi-physical model is defined in order to analyze the coupling of acoustics and fluid dynamics physics. The multi-physical model is used for different case studies of several geometries and Acoustic Metamaterial structures for noise reduction applications in ventilated ducts. Different geometrical shapes and Acoustic Metamaterial geometries (empty duct, narrowing cross-section, side-branch Helmholtz resonator, Acoustic Black Hole) are multi-physically characterized by the model presented in this work for Mechanical and Civil Engineering applications. Averagely, the effects of the multi-physical interaction of the presented numerical models provide deviation values of the Transmission Loss of 18dB. In particular, the methodology to investigate Acoustic Black H