The Acoustic-Solid Interaction, Frequency Domain Interface
The Acoustic-Solid Interaction, Frequency Domain interface (), found under the Acoustics>Acoustic-Structure Interaction branch () when adding a physics interface, combines the Pressure Acoustics, Frequency Domain 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.
A dedicated multiphysics coupling condition is readily defined for the fluid-solid boundary and sets up the fluid loads on the solid domain and the effect of the structural accelerations on the fluid. The interface exists for frequency domain and eigenfrequency studies.
The physics interface is available for 3D, 2D, and 2D axisymmetric geometries and has the capability to model pressure acoustics and solid mechanics in the frequency domain, including a special acoustic-solid boundary condition for the fluid-solid interaction.
When a predefined Acoustic-Solid Interaction, Frequency Domain interface is added from the Acoustics>Acoustic-Structure Interaction branch of the Model Wizard or the Add Physics windows, the Pressure Acoustics, Frequency Domain and Solid Mechanics interfaces are added to the Model Builder.
In addition, the Multiphysics node is added, which automatically includes the multiphysics coupling feature Acoustic-Structure Boundary.
See The Multiphysics Node and Multiphysics Modeling Approaches in the COMSOL Multiphysics Reference Manual.
On the Constituent Physics Interfaces
The Pressure Acoustics, Frequency Domain interface is used to compute the pressure variations when modeling the propagation of acoustic waves in fluids at quiescent background conditions. It solves the Helmholtz equation and is suited for all linear frequency-domain acoustic simulations with harmonic variations of the pressure field. The physics interface 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.
Settings for Physics Interfaces and Coupling Features
When physics interfaces are added using the predefined couplings, 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 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-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, Frequency Domain Interface are listed in the section Domain, Boundary, Edge, Point, and Pair Nodes for the Pressure Acoustics, Frequency Domain 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 Module User’s Guide
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Theory Background for the Pressure Acoustics Branch
Acoustic-Structure Interaction: Application Library path Acoustics_Module/Tutorials/acoustic_structure
Suggestions for setting up the solvers for solving large acoustic-structure interaction problems are given in Solving Large Acoustic-Structure Interaction Models in the Modeling with the Acoustic-Structure Interaction Branch section.