Basic Modeling Steps for Fluid-Structure Interaction

The following steps describe the basics of how to set up a model of fluid-structure interaction:

In the or window, select the interface. Click .

Select a study option—, , , or from the branch on the list; then click .


	If you also have the CFD Module, you can add a Stationary, One-Way Coupled with Initialization or Transient, One-Way Coupled with Initialization study for turbulence models requiring the wall distance. See Stationary, One-Way Coupled with Initialization and Transient, One-Way Coupled with Initialization in the COMSOL Multiphysics Reference Manual for more information.

Create the geometry, which should contain a fluid domain and a solid domain.

Add the materials, typically a fluid and a solid. Then assign the material added last to the domains that represents the solid (or the fluid, if the solid material was added first).

By default, the Fluid-Structure Interaction interface adds a node for the fluid domain as well as a node for the mesh displacements in the moving mesh to all domains in the geometry.

For the solid domain, the default is the node with the setting to include geometric nonlinearity and an initially empty selection.

To use another material model for the solid, from the toolbar, submenu, select a material node for the solid. Add the domains that represent the solid to its selection. That selection automatically overrides the and nodes in the solid.


	Typically, fluid-structure interaction means that there are large deformations. In this case, the Include geometric nonlinearity check box should be selected in the Study Settings section of the Settings window for the study.

Verify that the default boundary conditions are correctly assigned for the three types of boundaries in the model: the node for all fluid boundaries (and a node for zero mesh displacements on the same boundaries), the node for all solid boundaries, and the node on the interior boundaries between the fluid and the solid. The node implements the coupling from the force exerted on the solid boundary by the fluid as well as the as the structural velocities acting on the fluid as a moving wall.

Add additional boundary conditions as needed. Typically the fluid domain needs an node and an node for the inflow and outflow boundaries, respectively.

To add these nodes from the toolbar, submenu, select and (if the fluid is laminar). The solid domain needs some constraint such as a at some boundary.

Create the mesh and check that it resolves the domains sufficiently. A finer mesh might be needed other than what the default mesh settings provide.

To solve the problem, from the toolbar click . The solver settings might require some adjustments depending on the characteristics of the model.

Also add additional physics features to the model such as Thermal Expansion or Conjugate Heat Transfer, if applicable.


	Studies and Solvers in the COMSOL Multiphysics Reference Manual