System Coupling concepts#

A coupled analysis involves two or more participant solvers. System Coupling is responsible for coordinating the progress of each solution and for transferring variable data between the solver at appropriate points during the solution.

For example, in a Fluid-Structure Interaction (FSI) case, pressure data is transferred from the fluid to the structural solver, and displacement data is transferred from the structural solver to the fluid solver. Because each solver is generally working with a different mesh, the transfer of data involves a mapping of the data from one mesh to the other. System Coupling is responsible for performing this task.

Descriptions follow of the main concepts.


These are the solvers, representing different physics types, that are being coupled.


The participants expose variables. These are the quantities that are potentially available to be transferred.


The participants also expose the potential regions on which the data may be transferred. For example, in an FSI case, the relevant fluid regions would be the wall boundaries where pressure is being transferred to the structure.


These are the interfaces between participants.


Each interface has two sides.

Each side is associated with a participant and with a subset of the regions exposed by this participant.

Data transfers

Each interface must define at least one data transfer, which is a one-way transfer of a particular variable (such as pressure or displacement) between the two participants’ sides of the transfer’s containing interface. For a given transfer, one of the sides is regarded as the source of the data, and the other side is regarded as the target of the data. This defines the direction of the transfer.

A coupled analysis can be one-way or two-way, depending on whether transfers are defined in one or both directions on the interface.

Data model

Setting up a coupled analysis involves populating a hierarchical data model of settings. The data model closely follows the concepts that have been outlined here. For more information, see System Coupling data model.