Anisotropic Poroacoustics
The Anisotropic Poroacoustics node defines a domain with a porous material that has anisotropic properties. The material is modeled in a homogenized way using a so-called equivalent fluid model. Several models exist to define the attenuation and dispersion experienced by pressure waves as they propagate in the porous domain. Anisotropic properties can be defined for the relevant poroacoustic properties, namely the flow resistivity Rf, the tortuosity factor τ∞, and the viscous characteristic length Lv.
Three material models from the (isotropic) Poroacoustics feature exist for the anisotropic formulation (see below). These models define properties that result in an anisotropic effective density [ρ]ij and a scalar effective bulk modulus K. This is required for the formulation fit into the Anisotropic Acoustics framework.
For detailed modeling of anisotropic porous materials including the elastic porous skeleton, see the Anisotropic Poroelastic Material of the The Poroelastic Waves Interface.
Anisotropic Porous Absorber: Application Library path Acoustics_Module/Building_and_Room_Acoustics/anisotropic_porous_absorber
Coordinate System Selection
The Global coordinate system is selected by default. The Coordinate system list contains all applicable coordinate systems in the component. The coordinate system is used for interpreting directions of orthotropic and anisotropic material data when porous properties are presented in a local system.
Poroacoustics Model
Select the Poroacoustics model as Johnson-Champoux-Allard (JCA) (the default), Johnson-Champoux-Allard-Lafarge (JCAL), or Johnson-Champoux-Allard-Pride-Lafarge (JCAPL).
Fluid Properties
Enter the properties of the saturating fluid that is inside of the porous material. These settings are common to most porous models. By default the Fluid material uses the Domain material. Enter the following properties:
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Density ρf (SI unit: kg/m3) of the saturating fluid (the fluid density)
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Heat capacity at constant pressure Cp (SI unit: J/(kg·K)).
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Ratio of specific heats γ (dimensionless).
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Thermal conductivity k (SI unit: W/(m·K)).
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Dynamic viscosity μ (SI unit: Pa·s).
Porous Matrix Properties
In this section, enter the properties that describe the porous material. By default the Porous elastic material uses the Domain material (the material defined for the domain). Select another material as needed. For example, create your own material that contains the properties of a given porous material and refer to it here. Here, you also select the Porous matrix approximation as Rigid frame approximation or a Limp frame approximation for the porous material. The poroacoustic model defines complex-valued frequency-dependent expressions for both the bulk modulus and the equivalent anisotropic density.
In the Anisotropic Poroacoustics model, the Flow resistivity [Rf]ij, the Tortuosity factor [τ∞]ij, and the Viscous characteristic length [Lv]ij can have anisotropic properties. The remaining (isotropic) parameters are described in the relevant models in the Poroacoustics section.
For the three inputs, select either From material (the default) or User defined. For the User defined option, select if the material property is entered as Isotropic or Diagonal (the properties only have nonzero components in the diagonal for i = j). When taken From material, the properties can now be defined as diagonal tensor data, when defining a material in the Materials node.