The Acoustic-Piezoelectric Interaction, Transient Interface
The Acoustic-Piezoelectric Interaction, Transient interface (), found when adding a physics interface under the Acoustics>Acoustic-Structure Interaction branch (), combines the Pressure Acoustics, Transient and Piezoelectric Devices interfaces to connect and solve for the acoustic pressure variations in fluids with the structural deformation in both solids and piezoelectric solid domains. The physics interface also includes features from Electrostatics to solve for the electric field in the piezoelectric material. Examples include modeling piezoelectric transducers for sonar or medical applications and, for example, enhancing the impedance matching layers.
The pressure wave equation is solved in the fluid domain and the structural dynamic equations in the solid together with the constitutive relationships required to model piezoelectrics. Both the direct and inverse piezoelectric effects can be modeled, and the piezoelectric coupling can be formulated using the strain-charge or stress-charge forms.
When a predefined Acoustic-Piezoelectric Interaction, Transient 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 Electrostatics interfaces are added to the Model Builder.
In addition, the Multiphysics Couplings node is added, which automatically includes the Acoustic-Structure Boundary and Piezoelectric Effect multiphysics coupling features.
See The Multiphysics Branch and Multiphysics Modeling Approaches in the COMSOL Multiphysics Reference Manual.
On the Constituent Physics Interfaces
The Pressure Acoustics, Transient interface computes the pressure variations when modeling the propagation of acoustic waves in fluids at quiescent background conditions. The physics interface solves the scalar wave equation and is suited for time-dependent analyses with arbitrary time-dependent fields and sources. Domain conditions also include background incident acoustic fields. User-defined sources can be added to, for example, include certain nonlinear effects such as a square pressure dependency of the density variations.
The Piezoelectric Devices interface combines Solid Mechanics and Electrostatics together with the constitutive relationships required to model piezoelectrics. Both the direct and inverse piezoelectric effects can be modeled and the piezoelectric coupling can be formulated using the strain-charge or stress-charge forms.
Settings for Physics Interfaces and Coupling Features
When physics interfaces are added using the predefined coupling features, for example Acoustic-Structure Boundary, the Selection on the coupling feature is automatically set to All boundaries. In this way the multiphysics coupling is automatically active on all boundaries with Pressure Acoustics, Frequency Domain on one side and Solid Mechanics on the other.
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 the single interfaces are added, COMSOL Multiphysics adds an empty Multiphysics Couplings 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 Couplings 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-Structure Boundary coupling feature is described in the Multiphysics Couplings chapter. The Piezoelectric Effect is shortly described in The Piezoelectric Devices Interface.
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 Pressure Acoustics, Transient Interface are listed in the section Domain, Boundary, Edge, and Point Nodes for the Pressure Acoustics, Transient Interface
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The available physics features for The Solid Mechanics Interface are listed in the Structural Mechanics Module User’s Guide.
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The available physics features for The Electrostatics Interface are listed in the section Domain, Boundary, Edge, Point, and Pair Nodes for the Electrostatics Interface in the COMSOL Multiphysics Reference Manual.
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Some additional piezoelectric devices features for the Solid Mechanics and Electrostatics interfaces are described for The Piezoelectric Devices Interface.
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Theory section in the Structural Mechanics Module User’s Guide
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Theory of Electrostatics in the COMSOL Multiphysics Reference Manual
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Theory Background for the Pressure Acoustics Branch