Acoustic properties of porous media are very important for numerous industrial applications, the typical goal being to maximize broadband absorption to decrease the sound pressure level of the engineering system under consideration. Up to now acoustic absorption for porous media with complex inner geometry is determined experimentally, as acoustic simulations on the pore scale are computationally challenging due to the tedious geometric reconstruction of computer tomography (CT) data and the corresponding mesh generation as well as substantial computational requirements for the corresponding transient 3D solvers. The lattice Boltzmann method (LBM), which is an established computational approach to simulate pore-resolved porous media transport problems, has been used successfully for aeroacoustic setups and is utilized in this work to fill this gap. This paper presents a comparison of different experimental and numerical approaches to determine the acoustic absorption of different porous media. Experimental work with an impedance tube was carried out for comparison and CT scans were conducted to supply the detailed numerical simulation with geometry data of the porous samples. Results of LB simulations for the acoustic impedance of a microperforated plate and a felt are shown. Finally we demonstrate how microscopic parameters determined by a pore scale approach can be used to feed homogenized models to bridge the gap towards simulations of components where acoustic absorbers are applied to, e.g., wing flaps of airplanes.

中文翻译：

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结合孔隙解析模型和宏观模型来确定多孔介质的声吸收特性的分层方法

多孔介质的声学特性对于许多工业应用非常重要，典型的目标是最大限度地提高宽带吸收，以降低所考虑的工程系统的声压级。到目前为止，具有复杂内部几何形状的多孔介质的吸声是通过实验确定的，因为由于计算机断层扫描 (CT) 数据的几何重建和相应的网格生成以及大量的计算要求，孔隙尺度的声学模拟在计算上具有挑战性对于相应的瞬态 3D 求解器。格子玻尔兹曼方法 (LBM) 是一种已建立的用于模拟孔隙分辨多孔介质传输问题的计算方法，已成功用于气动声学设置，并在这项工作中用于填补这一空白。本文比较了不同的实验和数值方法，以确定不同多孔介质的吸声。使用阻抗管进行实验工作以进行比较，并进行 CT 扫描以提供详细的数值模拟和多孔样品的几何数据。显示了微孔板和毡的声阻抗的 LB 模拟结果。最后，我们展示了如何使用由孔隙尺度方法确定的微观参数来提供均质模型，以弥合对应用吸声器的组件（例如飞机的襟翼）进行仿真的差距。使用阻抗管进行实验工作以进行比较，并进行 CT 扫描以提供详细的数值模拟和多孔样品的几何数据。显示了微孔板和毡的声阻抗的 LB 模拟结果。最后，我们展示了如何使用由孔隙尺度方法确定的微观参数来提供均质模型，以弥合对应用吸声器的组件（例如飞机的襟翼）进行仿真的差距。使用阻抗管进行实验工作以进行比较，并进行 CT 扫描以提供详细的数值模拟和多孔样品的几何数据。显示了微孔板和毡的声阻抗的 LB 模拟结果。最后，我们展示了如何使用由孔隙尺度方法确定的微观参数来提供均质模型，以弥合对应用吸声器的组件（例如飞机的襟翼）进行仿真的差距。