The Acoustic-Solid Interaction, Transient Interface
The Acoustic-Solid Interaction, Transient interface (), found under the Acoustics>Acoustic-Structure Interaction branch () when adding a physics interface, combines the Pressure Acoustics, Transient and Solid Mechanics interfaces to connect the acoustics pressure variations in the fluid domain with the structural deformation in the solid domain. It can, for example, be used to determine the transmission of sound through an elastic structure or solve for the coupled vibroacoustics phenomena present in a loudspeaker.
Acoustic-structure interaction refers to a multiphysics phenomenon where the acoustic pressure causes a fluid load on the solid domain, and the structural acceleration acts on the fluid domain as a normal acceleration across the fluid-solid boundary.
Special physics interface conditions are readily defined at the fluid-solid boundary and set up the fluid loads on the solid domain and the effect of the structural accelerations on the fluid. The physics interface allows for transient studies but also solves in the frequency domain with the available boundary conditions.
When a predefined Acoustic-Solid Interaction, Transient interface is added from the Acoustics>Acoustic-Structure Interaction branch of the Model Wizard or the Add Physics windows, the Pressure Acoustics, Transient and Solid Mechanics interfaces are added to the Model Builder.
In addition, the Multiphysics Couplings node is added, which automatically includes the Acoustic-Structure Boundary multiphysics coupling feature.
See The Multiphysics Branch and Multiphysics Modeling Approaches in the COMSOL Multiphysics Reference Manual.
On the Constituent Physics Interfaces
The Pressure Acoustics, Transient interface is used to compute the pressure variations when modeling the propagation of acoustic waves in fluids at quiescent background conditions. It solves the scalar wave equation and is suited for time-dependent simulations 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 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.
For modeling of acoustic-structure interaction in the frequency domain, The Acoustic-Solid Interaction, Frequency Domain Interface contains additional functionality that is not applicable for modeling in the time domain.
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Theory section in the Structural Mechanics Module User’s Guide
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Theory Background for the Pressure Acoustics Branch
Settings for Physics Interfaces and Coupling Features
When physics interfaces are added using the predefined coupling features 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, Transient 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.
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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Theory section in the Structural Mechanics User’s Guide
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Theory Background for the Pressure Acoustics Branch