### 13.1.4. Restarting CFX Analyses as Part of System Coupling

Go to the section Restarting a System Coupling Analysis in the System Coupling User's Guide for the steps needed to restart a coupled analysis. To restart your coupled analysis, you will also need restart information specific to the participants connected to your System Coupling system.

For other participant systems connected to your System Coupling system, see Supported System Coupling Participants in the System Coupling User's Guide for a list of supported systems and references to their corresponding documentation regarding restarts. The sections below have information specific to restarting CFX in a coupled analysis:

- Generating CFX Restart Files
- Specify a Restart Point in CFX
- Making Changes in CFX Before Restarting
- Recovering the CFX Restart Point after a Workbench Crash
- Restarting from the Beginning of the Coupled Analysis

#### 13.1.4.1. Generating CFX Restart Files

A restart of a System Coupling analysis requires corresponding restart points to exist in the coupling service and in each of the solvers participating in the analysis.

CFX will automatically generate the corresponding backup (.bak) files based upon requests received from the System Coupling service. Note that these files are generated in addition to any other manually requested backup files (or results files) and are retained even if the Backup Data Retention option (Option in the CFX-Pre User's Guide) is set to `Delete Old Files`.

#### 13.1.4.2. Specify a Restart Point in CFX

When the CFX solution is restarted, the default behavior is that the results file (.res) corresponding to the current restart point will be used. To specify a different restart point:

1. In the Project Schematic, double-click CFX’s Solution cell to open the CFX-Solver Manager.

2. In the Define Run dialog box, select the Initial Values tab. For the Initialization Option, select Initial Conditions.

3. Enable the Initial Values Specification.

4. Next to File Name, select the browse icon ( ).

5. Browse to the backup files (.bak) or previous results file (.res), and select the file that matches the desired restart point. Backup files from a coupled analysis will have ”SC_ess” in their name.

   Make sure that you select the restart point that corresponds to the restart points selected for the System Coupling service and the other coupling participant.

   If the case that you are restarting was initialized from an independent CFX analysis, the time listed on the backup file (.bak) or results file (.res) might not match the corresponding restart points in System Coupling and the other participant system (such as Mechanical). Use the CFX-Solver output file to determine which time steps correspond to the System Coupling restart points.

6. Click Open to read-in the data for the selected restart point.

7. Continue History From can be enabled or disabled. Click Save Settings.

8. Close CFX by selecting File > Close CFX-Solver Manager.

#### 13.1.4.3. Making Changes in CFX Before Restarting

1. In the Project Schematic, double-click the CFX Setup cell. Make the needed setup changes in CFX-Pre.

2. Close CFX-Pre by selecting File > Close CFX-Pre.

#### 13.1.4.4. Recovering the CFX Restart Point after a Workbench Crash

1. In the Project Schematic, double-click CFX’s Solution cell to open the CFX-Solver Manager.

2. In the Define Run dialog box, select the Initial Values tab. For the Initialization Option, select Initial Conditions.

3. Enable the Initial Values Specification.

4. Next to File Name, select the browse icon ( ).

5. Browse to the backup files (.bak) or previous results file (.res).

6. If Workbench crashed while writing the final file, that file will be corrupt. In this case, select any of the previous files. Backup files from a coupled analysis will have ”SC_ess” in their name.

   Make sure that you select the restart point that corresponds to the restart points selected for the System Coupling service and the other coupling participant.

7. Click Open to read-in the data for the selected restart point.

8. Continue History From can be checked or unchecked. Click Save Settings.

9. Close CFX by selecting File > Close CFX-Solver Manager.

#### 13.1.4.5. Restarting from the Beginning of the Coupled Analysis

1. To restart the solution from the first time step, in the Project Schematic right-click System Coupling’s Solution cell and select Clear Generated Data.

2. Any initial values in the CFX system from a results file or backup file will continue to exist and be used in the CFX setup. You need to clear that data manually.

3. Restart the run from the System Coupling system.

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