The Fluid–Solid Interaction, Fixed Geometry Interface
The Fluid–Solid Interaction, Fixed Geometry () interface can be used to model phenomena where a fluid and a deformable solid structure 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, 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. Laminar Flow and Solid Mechanics interfaces are then added to the Model Builder.
In addition, the Multiphysics node is added, containing the multiphysics coupling Fluid–Structure Interaction.
On the Constituent Physics Interfaces
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The Laminar Flow interface is described in The Single-Phase Flow, Laminar Flow Interface. When the CFD Module is available, turbulent flow is supported through the inclusion of a number of turbulence models.
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The Solid Mechanics interface is described in The Solid Mechanics Interface.
You can add a Stationary, One-Way FSI or Time Dependent, One-Way FSI studies. See Stationary and Time Dependent One-Way FSI Studies for Fluid–Multibody Interaction in the COMSOL Multiphysics Reference Manual for more information.
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.
Table 15-7: Modified Settings for The Fluid–Solid Interaction, Fixed Geometry Interface.
Physics Interface or Coupling Feature
Modified Settings
Solid Mechanics
For the Solid Mechanics interface, under Discretization, the Displacement field is set to Quadratic Lagrange.
Laminar Flow
No changes.
Fluid–Structure Interaction
The Selection is set to All boundaries in the Boundary Selection section.
The corresponding Solid Mechanics and Laminar Flow interfaces are preselected in the Coupled Interfaces section.
The Fixed geometry coupling type is set to Fully coupled in the Fixed Geometry section.
Coupling Features
The Fluid–Structure Interaction coupling feature is used to couple the interfaces.