The Acoustic-Solid-Poroelastic Waves Interaction Interface
The Acoustic-Solid-Poroelastic Waves Interaction interface () combines Pressure Acoustics, Frequency Domain, Solid Mechanics, and Poroelastic Waves together with the Acoustic-Structure Boundary, Porous-Structure Boundary, and Acoustic-Porous Boundary multiphysics coupling feature.
On the Constituent Physics Interfaces
The Pressure Acoustics, Frequency Domain interface computes the pressure variations when modeling the propagation of acoustic waves in fluids at quiescent background conditions. The physics interface solves the Helmholtz equation and is suited for all linear frequency-domain acoustic simulations with harmonic variations of the pressure field. It includes domain conditions to model losses in a homogenized way, so-called fluid models for porous materials, as well as losses in narrow regions. The domain features also include background incident acoustic fields.
The Solid Mechanics interface is intended for general structural analysis of 3D, 2D or axisymmetric bodies. In 2D, the plane strain assumption should be used. The physics interface is based on solving Navier’s equations, and results such as displacements, stresses, and strains are computed.
The Poroelastic Waves interface is used to compute the displacement field and acoustic pressure fluctuation in porous materials with propagating poroelastic waves. Examples of applications include the propagation of elastic waves in rocks and soils, modeling the acoustic attenuation properties of particulate filters, characterizing sound absorbers and liners, or modeling the porous foams in headphones. The physics interface is valid for modeling the propagation of the coupled linear elastic and linear acoustic waves in the frequency domain. Harmonic variations of the displacement field and the sources are assumed. In the porous domains, Biot’s equations are solved accounting for the coupled propagation of elastic waves in the elastic porous matrix and pressure waves in the saturating pore fluid. This includes the damping effect of the pore fluid due to viscous losses only (the Biot model) or the combined effect of viscous and thermal losses (the Biot-Allard model).
When a predefined Acoustic-Solid-Poroelastic Waves Interaction interface is added from the Acoustics>Acoustic-Structure Interaction branch () of the Model Wizard or the Add Physics windows, the Pressure Acoustics, Frequency Domain, Solid Mechanics, and Poroelastic Waves interfaces are added to the Model Builder.
In addition, the Multiphysics node is added, which automatically includes the multiphysics coupling features Acoustic-Porous Boundary, Porous-Structure Boundary, and Acoustic-Structure Boundary.
See The Multiphysics Node and Multiphysics Modeling Approaches in the COMSOL Multiphysics Reference Manual.
Settings for Physics Interfaces and Coupling Features
When physics interfaces are added using the predefined coupling features, for example Acoustic-Solid-Poroelastic Waves Interaction, the Selection on the coupling feature is automatically set to All boundaries. In this way the relevant multiphysics couplings are automatically active on all relevant boundaries connecting two physics.
However, if physics interfaces are added one at a time, followed by the coupling features, these modified settings are not automatically included.
For example, if single Poroelastic Waves and Pressure Acoustics, Frequency Domain interfaces are added, COMSOL adds an empty Multiphysics node. You can choose the available coupling features, but you need manually to select on which boundaries they need to be applied, or select All boundaries to recover the predefined behavior.
Coupling features are available from the context menu (right-click the Multiphysics node) or from the Physics toolbar, Multiphysics menu.
Physics Interfaces and Coupling Features
Use the online help in COMSOL Multiphysics to locate and search all the documentation. All these links also work directly in COMSOL Multiphysics when using the Help system.
Coupling Feature
The Acoustic-Porous Boundary, Porous-Structure Boundary, and Acoustic-Structure Boundary coupling feature nodes are described in the Multiphysics Couplings chapter.
Physics Interface Features
Physics nodes are available from the Physics ribbon toolbar (Windows users), Physics context menu (Mac or Linux users), or right-click to access the context menu (all users).
In general, to add a node, go to the Physics toolbar, no matter what operating system you are using. Subnodes are available by clicking the parent node and selecting it from the Attributes menu.
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The available physics features for The Poroelastic Waves Interface are listed in the section Domain, Boundary, and Pair Nodes for the Poroelastic Waves Interfaces
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The available physics features for The Pressure Acoustics, Frequency Domain Interface are listed in the section Domain, Boundary, Edge, Point, and Pair Nodes for the Pressure Acoustics, Frequency Domain Interface