<p dir="ltr">Low frequency noise has been a challenge to noise control strategies for a long time due to its relatively long wavelength compared with practical thicknesses of acoustical treatments. A series of studies have drawn increasing attention to the acoustical behavior of porous granular materials such as activated carbon due to their good performance at low frequency. To better characterize this type of material, a 1-dimensional poro-elastic model is introduced in this work, which accounts for both the inner particle structure and the elasticity of the granule stack, allowing a better match of resonance features between the model prediction and measurement results. This model was then extended to a 2-dimensional finite difference (2DFD) approach under an axisymmetric assumption, with the depth-dependent stiffness of the granule stack considered. The shape of the computational domain of this 2DFD approach is close to the realistic geometry of the cylindrical standing wave tube, and it provides flexibility in assigning different types of boundary conditions at the circumferential wall of the container. The model is validated by comparing the simulation output and measurements of the acoustic response of porous granular materials in a cylindrical standing wave tube with rigid backing. The comparison demonstrates that the proposed 2DFD model is able to closely match the test results even down to detailed features, thus providing a means of accurate acoustic characterization of granular materials. The application scenarios of porous granular materials are also discussed in this work. A hybrid model based on the classical Johnson-Champoux-Allard (JCA) model and the rigid model describing the multi-level porosity within the granules is proposed to predict the performance of composite materials made of non-woven fiber matrices and porous granular materials. The performance of other practical applications such as that of a sound absorber consisting of a membrane and a cavity partially filled with the porous granular material is also discussed. These applications are shown to be promising strategies of addressing the low frequency noise problems.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/24749712 |
| Date | 06 December 2023 |
| Creators | Zhuang Mo (17584011) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/A_Poro-Elastic_Model_for_Porous_Granular_Materials/24749712 |
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