The Fluid–Solid Interaction, Viscoelastic Flow, Fixed Geometry Interface
Using the Fluid–Solid Interaction, Viscoelastic Flow, Fixed Geometry () interface, you can model phenomena where a deformable solid and a fluid exhibiting a combination of viscous and elastic behavior affect each other. Both the fluid loading on the structure and the structural velocity transmission to the fluid can be taken into account. The interface models situations where the displacements of the solid are assumed to be small enough for the geometry of the fluid domain to be considered as fixed during the interaction.
You add a predefined Fluid–Solid Interaction, Viscoelastic Flow, Fixed Geometry interface from the Fluid–Structure Interaction () group in either the Structural Mechanics branch () or the Fluid Flow branch () of the Model Wizard or Add Physics windows. Viscoelastic Flow and Solid Mechanics interfaces are then added to the Model Builder.
In addition, the Multiphysics node is added to the Model Builder, which automatically includes the multiphysics coupling feature Fluid–Structure Interaction.
The Viscoelastic Flow interface solves the continuity equation for conservation of mass and the Navier–Stokes equations for the conservation of momentum with an additional elastic stress term. To calculate the extra stress tensor, a number of constitutive relations are available.
The solid domain has all functionality available in the Solid Mechanics interface, including contact conditions and also nonlinear materials if the Nonlinear Structural Materials Module or Geomechanics Module is available.
On the Constituent Physics Interfaces
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The Solid Mechanics interface is described in The Solid Mechanics Interface.
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The Viscoelastic Flow interface is described in The Viscoelastic Flow Interface.
Settings for Physics Interfaces and Coupling Features
When physics interfaces are added using the predefined couplings, all specific settings are included with the physics interfaces and the coupling features.
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 Laminar Flow and Solid Mechanics interfaces are added, COMSOL Multiphysics adds an empty Multiphysics node. You can choose from the available coupling features, but the modified settings are not included.
Coupling features are available from the context menu (right-click the Multiphysics node) or from the Physics toolbar, Multiphysics Couplings 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 Features
 The Fluid–Structure Interaction feature is used to couple the interfaces.
Physics Interface Features
Physics nodes are available from the Physics ribbon toolbar (Windows users), Physics context menu (macOS 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.