Design and analysis of tunable acoustic louvers using an opensource finite element platform

In this study, the acoustic scattering problem was solved using the open-source finite element analysis platform, FEniCS. Modular scripts were written in the web-based interactive command-line Jupyter Notebook, which can also be integrated with various libraries to create a solution package for related engineering problems. The GMSH library, which provides high control and precision for creating meshes and defining boundary conditions for two-dimensional geometries, was used. The infinite solution domain of the external Helmholtz problem describing open space was truncated using the absorbing boundary condition and a finite solution domain was created. Error analyses were carried out for the Sommerfeld, BGT-1, and BGT-2 absorbing boundary conditions. It became possible to optimize the meshes created based on design variables. An optimization algorithm package was developed based on parameter-sweep and the Nelder-Mead methods. A crescent-shaped section with low sensitivity to small geometric changes and high sound attenuation performance is proposed as a result of the optimization analyzes adapted for single and multiple scattering problems. When evaluated with the error analyses, it was found that the use of the Sommerfeld ABC was sufficient for the purpose of the study. Thus, an additional software package was prepared to calculate the insertion losses of acoustic louvers used in noise control studies. With this software package, incident and total wave are separated into standard octaves using weighting and spectrum density filters. The results showed that the critical frequency is sensitive to the thickness of the acoustic louver. It is thought that this open-source software package can be used in the future to design acoustic metamaterials.