17.6.2.30. Fluid Solid Interface

A Fluid Solid Interface boundary condition is used to identify the surface region where the transfer of loads to and from external fluid solvers CFX or Fluent occur.

This page includes the following sections:

Analysis Types

Fluid Solid Interface is available for the following analysis types:

Important:  If you are using System Coupling to perform coupled simulations, Ansys recommends that you use the System Coupling Region object to define the interfaces.

Note:

  • A Static Structural analysis coupled with other physics is intended to work with one substep (specified in the Analysis Settings). When a Fluid Solid Interface is present, program controlled sub-stepping will always use one substep regardless of any nonlinearities present. See Steps and Step Controls for Static and Transient Analyses under the Configuring Analysis Settings section of the Help.

  • When one or more FSI loads are present:

    • Any components defined in the Mechanical APDL input file are exported using the CMWRITE command to the file, file.cm, before the solution is completed. This aids the post-processing of results in CFD-Post.

    • The Environment object provides the context menu (right-click) option, Write System Coupling Files. For supported analysis types, this option creates an input (.dat) file as well as a System Coupling Participant (.scp) file that is needed to run a System Coupling analysis using one of System Coupling's user interfaces.

  • There is currently a limitation associated with making a name change to your Fluid Solid Interface object in Mechanical. The Setup cell on the Project Schematic for System Coupling is not automatically updated. You need to perform an action in the application in order to update the Setup cell so that it receives the new name.

Mechanical Structural - Fluent

Fluid-solid interfaces define the interfaces between the solid or shell elements in the Mechanical system and the fluid in the Fluent system. These interfaces are defined on faces in the Mechanical model. During the execution of the simulation, System Coupling orchestrates the exchange of data across these interfaces, allowing the Mechanical application and Fluent to send boundary condition results back and forth to one another (one or two-way communication is available).

Mechanical's Static Structural and Transient Structural systems can be coupled with Fluent for a fluid force and structural displacement analysis, or a fluid-thermal-structural analysis. For more information about settings and elements needed for the thermal-structural analysis, see Coupled Field Co-Simulation Using System Coupling.

The integer Interface Number, found in the Details pane, is incremented by default each time a new interface is added. This value can be overridden if desired.

Note:  For Coupled Field Static and Coupled Field Transient analyses, the application defines interfaces between acoustic and structural regions using the Fluid Solid Interface object. To define the interaction between elements in Mechanical and Fluent, use the System Coupling Region object.

Mechanical Acoustics

Fluid-solid interfaces define the interfaces between the acoustic and the structural regions. These interfaces are defined on acoustic region faces. You can use the contextual (right-click) menu option Create Automatic > FSI on the environment object to automatically identify Fluid Solid Interfaces.

Mechanical Thermal - Fluent

Fluid-solid interfaces define the interfaces between the thermal solid or shell elements in the Mechanical system and the fluid in the Fluent system. These interfaces are defined on faces in the Mechanical model. Data is exchanged across these interfaces during the execution of the simulation as described in Fluid-Structure Interaction (FSI) - One-Way Transfer Using System Coupling.

For transferring temperature and heat flows from Mechanical, interfaces may only be defined on the following types of faces:

  • On faces having heat fluxes.

  • On faces having convections.

  • On faces with a temperature load.

  • On faces without any loads specified (adiabatic). In this case, only temperatures are exchanged.

Dimensional Types

The supported dimensional types for the Fluid Solid Interface boundary condition include:

  • 3D Simulation

Geometry Types

The supported geometry types for the Fluid Solid Interface boundary condition include:

  • Solid

  • Surface/Shell

Topology Selection Options

The supported topology selection options for Fluid Solid Interface include:

  • Face

Applying a Fluid Solid Interface Boundary Condition

To apply a Fluid Solid Interface:

  1. Based on the analysis type, from the Environment Context tab, select the Fluid Solid Interface option from either the Loads or Conditions drop-down menu. Alternatively, right-click the Environment tree object or in the Geometry window and select Insert>Fluid Solid Interface.

  2. Define the scoping for the object. Face scoping is supported either through geometry picking or the use of a Named Selection.

Details Pane Properties

The selections available in the Details pane are described below.

CategoryProperty/Options/Description
Scope Scoping Method: Options include:

  • Geometry Selection: Default setting, indicating that the boundary condition is applied to a geometry or geometries, which are chosen using a graphical selection tool.

    • Geometry: Visible when the Scoping Method is set to Geometry Selection. Displays the type of geometry (Face) and the number of geometric entities (for example: 2 Faces) to which the boundary has been applied using the selection tools.

  • Named Selection: Indicates that the geometry selection is defined by a Named Selection.

    • Named Selection: Visible when the Scoping Method is set to Named Selection. This field provides a drop-down list of available user-defined Named Selections.

Definition

Type: Read-only field that displays boundary condition type - Fluid Solid Interface.

Interface Number: Incremental value for each new interface. This value can be overridden if desired.

Export Results: Thermal analyses only. The default value for this property is No. When this property is set to Yes, thermal data is written to .axdt files for use with External Data and System Coupling, which can connect to Fluent to transfer thermal data to a CFD analysis for a one-way transfer of static data. The file format for an External Data File (.axdt) is described in the External Data File Format Help section in the Workbench User Guide.

Data to Transfer [Expert]: The default for this property is Program Controlled. When set to All System Coupling Data Transfers, the fluid solid interface regions can participate in force, displacement, and thermal coupling through System Coupling. You need to set All System Coupling Data Transfers for Mechanical to participate in a thermal-structural analysis.

Suppressed: Include (No - default) or exclude (Yes) the boundary condition.

API Reference

For specific scripting information, see the Fluid Solid Interface section of the ACT API Reference Guide.