Publicação
Avaliação numérica e experimental de barreiras acústicas periódicas com perdas visco-térmicas
| Resumo: | In the last decades, concern about noise and its harmful effects on populations has increased significantly. In light of this concern, buildings located near traffic routes require greater attention, as they are often exposed to high sound pressure levels. Thus, there is a growing need to study and define potential mitigation measures, including the development of noise barriers capable of significantly reducing sound pressure levels near building façades. Recently, the use of unconventional materials and geometries has been proposed for the design of noise barriers for traffic noise protection, although practical applications remain limited. For this purpose, the concept of sonic crystals applied to acoustic barriers has emerged as a promising strategy, as these structures can enhance sound attenuation within a specific frequency range (known as a bandgap).With the aim of developing a more effective unconventional noise barrier, a two-dimensional numerical model based on the Method of Fundamental Solutions (MFS) was initially implemented to evaluate the acoustic performance of devices with various geometric configurations and material compositions. To validate this model, a reduced-scale prototype of the barrier was built and tested in a semi-anechoic chamber at the Department of Civil Engineering of FCTUC. In addition to experimental validation, numerical verification was carried out using the Finite Element Method (FEM), and results were compared with those obtained through the Singular Boundary Method (SBM).Subsequently, three-dimensional numerical models were developed using the FEM and validated through laboratory experiments conducted in the same semi-anechoic chamber. Parametric analyses were performed to evaluate the influence of geometric parameters and assembly conditions of the barriers. Given the small-scale geometry of the barriers used to validate the 2D MFS model, the effects of visco-thermal losses were also studied in order to analyze the correlation between the numerical predictions and experimental data. In such cases, to accurately predict the physical behavior of these systems, more complex and computationally demanding numerical models are required. Among these, the use of the Navier–Stokes equations as governing equations rather than the linear Helmholtz equation is particularly noteworthy.To enable the application of these advanced approaches, techniques such as the Boundary Layer Impedance (BLI) method were used in conjunction with the MFS or other meshless methods better suited for capturing visco-thermal losses efficiently. These methodologies were implemented computationally and validated by comparing the results with those obtained using commercial finite element software (e.g., COMSOL Multiphysics) and experimental data obtained under controlled laboratory conditions.Finally, the effect of adding granular-type absorbing materials, such as porous concrete, was assessed. These analyses examined the influence of the acoustic properties of porous concrete on the insertion loss (IL) of sonic crystal noise barriers and proposed optimized configurations concerning the thickness of the porous concrete to achieve a broader bandgap in the frequency range of interest. |
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| Autores principais: | Veloso, Matheus Duarte |
| Assunto: | sonic crystals visco-thermal losses acostic barriers MFS perdas visco-térmicas MFS barreiras acústicas cristais sónicos - - |
| Ano: | 2025 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Coimbra |
| Idioma: | português |
| Origem: | Estudo Geral - Universidade de Coimbra |
| Resumo: | In the last decades, concern about noise and its harmful effects on populations has increased significantly. In light of this concern, buildings located near traffic routes require greater attention, as they are often exposed to high sound pressure levels. Thus, there is a growing need to study and define potential mitigation measures, including the development of noise barriers capable of significantly reducing sound pressure levels near building façades. Recently, the use of unconventional materials and geometries has been proposed for the design of noise barriers for traffic noise protection, although practical applications remain limited. For this purpose, the concept of sonic crystals applied to acoustic barriers has emerged as a promising strategy, as these structures can enhance sound attenuation within a specific frequency range (known as a bandgap).With the aim of developing a more effective unconventional noise barrier, a two-dimensional numerical model based on the Method of Fundamental Solutions (MFS) was initially implemented to evaluate the acoustic performance of devices with various geometric configurations and material compositions. To validate this model, a reduced-scale prototype of the barrier was built and tested in a semi-anechoic chamber at the Department of Civil Engineering of FCTUC. In addition to experimental validation, numerical verification was carried out using the Finite Element Method (FEM), and results were compared with those obtained through the Singular Boundary Method (SBM).Subsequently, three-dimensional numerical models were developed using the FEM and validated through laboratory experiments conducted in the same semi-anechoic chamber. Parametric analyses were performed to evaluate the influence of geometric parameters and assembly conditions of the barriers. Given the small-scale geometry of the barriers used to validate the 2D MFS model, the effects of visco-thermal losses were also studied in order to analyze the correlation between the numerical predictions and experimental data. In such cases, to accurately predict the physical behavior of these systems, more complex and computationally demanding numerical models are required. Among these, the use of the Navier–Stokes equations as governing equations rather than the linear Helmholtz equation is particularly noteworthy.To enable the application of these advanced approaches, techniques such as the Boundary Layer Impedance (BLI) method were used in conjunction with the MFS or other meshless methods better suited for capturing visco-thermal losses efficiently. These methodologies were implemented computationally and validated by comparing the results with those obtained using commercial finite element software (e.g., COMSOL Multiphysics) and experimental data obtained under controlled laboratory conditions.Finally, the effect of adding granular-type absorbing materials, such as porous concrete, was assessed. These analyses examined the influence of the acoustic properties of porous concrete on the insertion loss (IL) of sonic crystal noise barriers and proposed optimized configurations concerning the thickness of the porous concrete to achieve a broader bandgap in the frequency range of interest. |
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