Set up the System Coupling portion of the coupled analysis using the sub-nodes and corresponding properties available under the Setup node, which is defined in the System Coupling tab's Outline.
The state of the Setup node reflects the state shown by the
System Coupling system's Setup cell on the Project
Schematic. Validation of the Setup node depends upon the
validation of the individual sub-nodes defined under it (for example, Analysis
Settings and Data Transfer). If any of these sub-nodes is
invalid, then the Setup node is also invalid, as shown by the state of
Attention Required (
).
Tip: If the Workbench setup will be exported for execution in one of System Coupling's user interfaces, then proceed according to the capabilities that are required for the analysis. Available capabilities are determined by the timing of the export, as described in Exporting Partial vs. Full Coupling Setups.
For more information, see Exporting a System Coupling Setup and Running an Exported System Coupling Setup.
To access System Coupling properties, right-click the Setup node and select Expand All.
Use the following Setup node functionality to complete your coupled analysis setup:
Use the Setup node's context options to perform various set-up tasks. To access available options, right-click a sub-node defined under the Setup node.
Available options:
- Expand All / Contract All
Available for all nodes. Expands or contracts all nodes in the Outline.
- Start/Stop highlighting linked nodes
Available for the Setup node. Controls whether nodes related to the selected node are highlighted in the Outline.
- Create Data Transfer
Available for the Data Transfers container node. Creates a new data transfer. For details, see Data Transfer Context Options.
- Rename
Available for data transfer nodes. Renames the selected data transfer. For details, see Data Transfer Context Options.
- Duplicate
Available for data transfer nodes. Duplicates the selected data transfer. For details, see Data Transfer Context Options.
- Display Validation Failure
Available for any node that is invalid, as indicated by a state of Attention Required (
). Displays error messages with details on
validation problems.- Add Property
Available for the Execution Control > Expert Settings node. Allows you to select and enable an expert setting. Once enabled, the setting is displayed under Properties whenever the Expert Settings node is selected. For more information, see Expert Settings.
- Remove Property
Available for the Execution Control > Expert Settings node when an expert setting is enabled. Allows you to select and disable an expert setting. Once disabled, the setting is removed from Properties. For more information, see Expert Settings.
- Read restart points
When Analysis Settings is selected in the Outline, available for the Coupling Initialization property under Properties. Populates the list of restart points.
Useful for atypical situations such as a Workbench crash, when the restart point list may be empty even though the intermediate restart files exist on your disk. Repopulating the list of restart points allows you to restart from a previously saved point.
- Export System Coupling Setup
Available for the Setup node when participant systems have been connected to the System Coupling system and their physics setups are complete (that is, their Setup cells are in an up-to-date state).
Note: You can also access this option on the Project Schematic by right-clicking the System Coupling system's Setup cell.
Exports the files needed for a user-interface run to a specified working directory. For more information, see Exporting a System Coupling Setup.
Use the Setup node's coupling-specific properties to define analysis details. To access properties, select any of the sub-nodes defined under Setup. Any properties associated with the selected node are displayed below under Properties, where you can edit the properties that are enabled.
Coupling properties are defined under the following nodes:
Defines the basic behavior of the analysis. When Analysis Settings is selected, the following properties are shown below under Properties:
Property defining the type of the analysis.
Possible values:
General
Used when all participants are executing a steady-state or static solution.
Transient
Used when any participant is executing a transient solution (includes mixed steady-transient analyses).
- Coupling Initialization
Property controlling how the analysis is initialized:
Possible values:
Program Controlled
For initial runs (that is, not restart runs), the initial time and step are each set to 0.
For restart runs, the initial time and step are set to the values obtained from the most recent valid restart point.
Restart Points (indicated by Step and Time)
A coupled simulation can have multiple restart points when Intermediate Restart Data Output is selected for either all coupling steps or for a set of coupling step intervals. The next coupled analysis will be started based on the restart point you select.
For more information, see Restarting a Coupled Analysis in Workbench.
Important: Program-controlled or explicitly specified restart points affect only the coupling step and/or time used to restart System Coupling. Appropriate restart points must also be specified for the co-simulation participants that are part of the coupled analysis.
The duration of the analysis is defined by the following properties.
- Duration Defined By
Property controlling how the duration of the analysis is defined:
Possible values:
End Time
Available when the Analysis Type is Transient
System Coupling executes coupling steps until the end time specified by the End Time property is reached. In a transient analysis, each coupling step is a time step (with the time interval specified by the step size). Note that the final coupling step size is reduced automatically, if needed, so that the specified end time is respected.
Note: Some participant systems, such as Mechanical, require that the end time specified in their setup is respected. When a coupled analysis involves one or more participants that require their end time to be respected, then the maximum allowable end time for the coupled analysis is the minimum of the end times reported by such participants. In this case, a validation error will be reported if the coupled analysis' specified end time is greater than the minimum identified.
Other participant systems, such as Fluent, can run past the end time specified. These participant systems have no effect on the allowable end time of the coupled analysis.
Number of Steps
Available when the Analysis Type is General.
System Coupling executes coupling steps until the number of steps specified by the Number of Steps property have been executed.
- End Time [s]
Available when Duration Defined by is set to End Time. Property defining the duration of the analysis.
Required. A value must be specified before a Solve operation is attempted.
Default value is None. Accepts real values greater than 0.0.
If units are not specified, seconds [s] are used.
- Number of Steps
Property defining the number of coupling steps in the analysis. Available when Duration Defined by is set to Number of Steps.
The duration of the coupled analysis is broken into a sequence of coupling steps. Data transfers between the coupled solvers occur at the beginning of each coupling iteration within a coupling step. Coupling steps are always indexed. During the analysis, each new coupling step is started when:
The coupling analysis duration has not been reached, and
Either the maximum number of coupling iterations has been reached or the coupling step has converged.
The coupling steps of the analysis are defined by the following properties:
- Step Size
Available when the coupling is defined in terms of time (a transient analysis). Property defining the time interval associated with each coupling step.
Default value is None. Accepts real values greater than 0.0.
If units are not specified, seconds [s] are used.
Note: The final coupling step size is reduced automatically, if needed, so that the specified end time is respected. This reduction does not occur if the analysis duration is set by the Number of Steps.
The coupling step size is fixed for the duration of the coupled analysis but can be changed when restarting the analysis.
- Minimum Iterations
Property defining the fewest number of coupling iterations that can be executed per coupling step (must be at least 1).
The specified minimum number of coupling iterations is executed even if all measures of convergence are realized in fewer iterations.
- Maximum Iterations
Property defining the greatest number of coupling iterations that can be executed per coupling step.
The specified maximum number of coupling iterations may not be executed if the analysis converges before the maximum iteration step is reached.
Defines the participants involved in the analysis.
Under the Participants node, a read-only sub-node is defined for each participant connected to System Coupling system's Setup cell on the Project Schematic. The sub-node takes the participant name, as presented in the Project Schematic
Under a given participant node, a Regions node is defined.
Defines the regions for the participant. Contains a collection of participant regions from/to which data can be transferred.
A region is most often a point, line, surface, or volume that is part (or all) of the participants geometry or topology. Note, however, that equations or probe (monitored) values may also be considered as point regions.
Note: System Coupling in Workbench requires participants to use 3D meshes, with data transfer regions consisting of element faces from a 3D mesh. System Coupling, when run from one of its user interfaces, supports both 2D and 3D meshes.
When a given region is selected, the following properties are shown below under Properties.
- Topology
Property indicating the topology of the region. Currently, the only available value is Surface.
Note: Volume regions are available for GUI or CLI-based co-simulations with Maxwell as a participant.
- Input Output
Property indicating the variable (such as force, length, or temperature) transferred to/from the region.
- Physical Type
Property indicating the quantity transferred to/from the region.
Defines the data transfers to be performed in the analysis.
System Coupling in Workbench defines a data transfer as one source region and one target region, with the transfer of one variable type in one direction between two participants. For a two-way data transfer on one region, two individual data transfers are defined.
Note: For data transfer creation rules applicable to both System Coupling and System Coupling in Workbench, see Rules for the Creation of Data Transfers.
Under the Data Transfers node, a sub-node is defined for each data transfer created. When a given data transfer is selected, the following properties are shown below, under Properties:
Data transfer source and target are defined by the following properties:
- Source/Target
Defines the Source and Target for the data transfer. Both are defined by the following properties:
- Participant
Defines the participant associated with the data transfer.
- Region
Defines the region to/from which data are transferred.
- Variable
Defines the variable to be transferred.
When setting up data transfers, follow a top-down approach when defining Source and Target. Select in this order:
Source Participant
Source Region
Source Variable
Target Participant
Target Region
Target Variable
Data transfer behavior is defined by the following properties:
- Transfer At
Controls when the data transfer is executed by the solver. Only available option:
Start of Iteration
Transfer data at the start of every coupling iteration within a coupling step.
- Under-Relaxation Factor
Factor multiplying the current data transfer values when under-relaxing them against the previous values. This is overridden with unity in the first coupling iteration of every coupling step only when the Analysis Type is Transient.
For more detailed information, see Under-Relaxation Algorithm.
Note:Ramping and under-relaxation are independent operations. Ramping is applied before under-relaxation.
When under-relaxation is used, there is no guarantee that the full value from the source side of the data transfer is applied to the target by the end of the coupling step.
- RMS Convergence Target
Target value used when evaluating convergence of the data transfer within a coupling iteration. The default value is 1e-2. The convergence target is RMS-based. For information regarding how this target is applied, see Evaluating Convergence of Data Transfers.
- Ramping
Determines the behavior of the ramping algorithm for specified quantity.
Ramping is used by System Coupling to slow the application of the source-side value on the target side of the interface.
Possible values:
None
No ramping is applied. The full data transfer value is applied to the target side of the interface for all coupling iterations. (default value)
Linear to Minimum Iterations
Within each coupling step, the ramping factor is used to linearly increase the change in the data transfer value applied to the target side of the interface.
For more information on the ramping algorithm, see Ramping Algorithm.
Note: System Coupling's ramping interacts with the ramping behaviors of the participant systems. To understand the full ramping behavior, verify ramping settings to see if your participant system is ramping loads received from System Coupling. For ramping behavior in Mechanical, see System Coupling Related Settings in Mechanical in the Mechanical User's Guide.
After you connect a participant system's Setup cell to the System Coupling Setup cell in the Project Schematic and refresh the Setup cell, context options for creating and manipulating data transfers are available.
To access these context options, right-click the Data Transfers node or any specific data transfer defined underneath it.
Available options:
- Create Data Transfer
Use to create single and multiple data transfers in any of the following ways:
Create an uninitialized data transfer:
Right-click Data Transfers and select Create Data Transfer. This creates a new data transfer without any source or target properties defined. You can change the data transfer definition later, in Properties pane.
Create data transfers for two regions from different participants:
Multi-select two regions from different participants, right-click one of them and select Create Data Transfer. This creates multiple data transfers that vary based on the following criteria:
Whether the two regions have the same topology
Whether the input variable from one region has the same properties (such as the physical type) as the output variable from the other region
Create data transfers for a single region:
Right-click a single region and select Create Data Transfer. This creates data transfers for each variable associated with the region. If the variable is an output variable, then the source participant, source region, and source variable are defined for the new data transfer. If the variable is an input variable, then the target participant, target region, and target variable are defined for the new data transfer.
Create a data transfer for a single variable:
Select a region, then right-click a variable under Properties pane and select Create Data Transfer. This creates a new data transfer. If the selected variable is an output variable, then the source participant, source region, and source variable are defined for the new data transfer. If the selected variable is an input variable, then the target participant, target region, and target variable is defined for the new data transfer.
- Rename
Right-click a data transfer, select Rename, type in the new name, and click Enter. Alternatively, you can double-click a data transfer to rename it.
- Duplicate Data Transfer
Select one or more data transfers, right-click one of them, and select Duplicate. This operation creates new data transfers with the same Source, Target, and Data Transfer Control properties. Note that you can change these properties as needed.
- Delete
Select one or more data transfers, right-click one of them, and select Delete.
- Suppress
Select one or more unsuppressed data transfers, right-click one of them, and select Suppress.
- Unsuppress
Select one or more suppressed data transfers, right-click one of them, and select Unsuppress.
Note: If the data transfer definition is not valid or the data are invalidated for any reason,
the state of the node shows as Attention Required ( ).
Provides the following properties to control the execution of the coupled analysis.
The Coupling Engine property is available only for coupled analyses created using System Coupling 1.0, which has been removed as of the 2020 R2 release. When Execution Control is selected, the Coupling Engine property is shown under Properties.
The purpose of the Coupling Engine property is to allow you to set the analysis to run with the current release of System Coupling (2.0). The only value possible is 2.0.
To continue working with a 1.0 simulation using the 2020 R2 release, you must set the Coupling Engine property to 2.0 for each System Coupling system on the Project Schematic.
When this value is selected and saved, the current version of the System Coupling engine will be used to run the analysis. This entails the following changes:
All data previously generated for the case are cleared.
Once switched, the case cannot be reverted back to compatibility with System Coupling 1.0.
After this System Coupling session is ended, the Coupling Engine property will no longer be available.
Note: If you wish to continue working with the case as it is (that is, without switching it to use the 2.0 coupling engine, as described above), then you must use a pre-2020 R2 release of System Coupling. If you do not switch to the 2.0 coupling engine and attempt to proceed using the case with the 2020 R2 release, updating the Solution cell of a System Coupling system will raise an error.
Expert settings provide you with advanced controls for some System Coupling properties. For more information, see:
- To enable an expert setting:
In System Coupling Outline, expand Execution Control.
Right-click Expert Settings and select Add Property.
Select the expert setting to be enabled.
The selected setting is shown under Properties with a value of True (enabled).
- To edit an enabled expert setting:
In Outline, select Expert Settings.
Under Properties, select a different value for the setting.
The setting value is changed.
- To disable an expert setting:
In Outline, right-click and select .
Select the expert setting to be disabled.
The setting is removed from Properties.
The following expert settings are available when using System Coupling in Workbench:
- ExportInterfaceDataPerStep
When enabled, generates interface/data transfer diagnostics files for each coupling step. At the end of the final iteration of each coupling step, System Coupling generates two .axdt files for each data transfer, with one file for each participant, to its working directory.
For a given step, these files include the mesh for all nodes (mapped and unmapped) and the results for data transfer variables corresponding to the final coupling iteration in that step.
Disabled by default.
- GlobalStabilization
When enabled, Quasi-Newton stabilization is used for the coupled analysis. System Coupling in Workbench supports only default global stabilization settings. For more information, see Quasi-Newton Stabilization Algorithm.
Tip: To access the full functionality of the Quasi-Newton algorithm, you may export the coupling setup from Workbench so the analysis can be executed in System Coupling's GUI or CLI. For details, see Exporting a System Coupling Setup and Running an Exported System Coupling Setup.
- WriteDiagnosticsDictionary
When enabled, generates mapping weight and interpolation diagnostic files. System Coupling writes the following .json files to the Solution Information pane and its working directory:
A single weightsDiagnostics_step<
#>.json file is generated during the first iteration of the first step of the coupled analysis. For a given interface, this file contains weights diagnostics for the mapping process of that interface.An interpolationDiagnostics_step<
#>_iteration<#>.json file is generated for every iteration in the coupled analysis. For a given step, these files contain full interpolation diagnostics. Contents include mesh and results — specifically, the mapped/unmapped mesh locations and data transfer variable(s) corresponding to the final iteration of the step.
Enabled by default.
- Source_InitValue_HeatTransferCoef
Sets the initial source value for a Heat Transfer Coefficient variable. When enabled, specified initial value is used as the raw variable value provided by the source participant to initialize the simulation (that is, for the first iteration of the first step of the simulation).
If an actual raw value has been provided by the source participant, the specified initial value overrides it.
Accepts real values 0.0 ≤ x ≤ 1e+30. Default value is 0.0.
When Intermediate Restart Data Output is selected, the following properties allow you to define details about the restart data generated during the execution of the solution:
- Output Frequency
Specify the frequency with which restart files are generated.
Possible values:
None
No intermediate restart output files are generated using this option. (default value)
All Steps
Restart output files are generated at the end of each coupling step.
At Step Interval
Restart output files are generated at the end of the coupling steps corresponding to the interval specified by the Step Interval property.
- Step Interval
Available when Output Frequency is set to At Step Interval. Specifies the interval at which restart files are generated. For example, with a value of 3, System Coupling generates a restart point at the end of every third coupling step.
Accepts integer values greater than or equal to 1. Default value is 1.
Note: Depending on the participant, the restart data may or may not be the same as the results data. Writing of results data for postprocessing should be set from within the participant Setup cell.
Important: During execution of the coupled analysis, co-simulation participants are automatically requested to generate intermediate restart data at the same frequency as System Coupling. Note that this feature only affects the frequency at which data are generated. The content of data is determined by the participant.