Troubleshoot convergence (external restart)

Troubleshoot convergence

To troubleshoot convergence, after the initial run, you adjust boundary conditions and solver parameters, and then you set the solution to use the initial run results to generate restart results. Repeat this as many times as necessary. The results are saved up to the last point of convergence, so you can use those results for the next solve. In other words, the restart data .op2 file is cumulative.

Note:

The solver overwrites the restart run results each time, so if you want to save any results before the next restart run, rename the .op2 file.

1. Create your initial run solution with the necessary subcases and solver parameters. For information on creating a solution, see Creating and managing solutions and subcases.

2. In the Solution dialog box, on the Restart Management page, set Generate Restart Data to Yes.

3. Right-click the initial run solution and choose Solve.The data for the restart run is saved at the end of the subcase and at the last converged time step.

4. View the results in post-processing to determine which subcase and time step failed.For more information, see Post-processing.

5. In the same Simulation file that you used for the initial run, right-click the initial run solution and choose Clone.

6. Rename the solution with a unique name.

7. Adjust boundary conditions, deactivate contact, and change subcase parameters such as time steps. For example, you might adjust loads and time step increments. You cannot, however, modify the mesh or material properties, and you cannot add new contact and glue conditions. If you do so, the solution will fail the model check. Note: The initial run and restart run models should match. Sometimes, however, you may need to modify the model to ensure convergence. For example, you may need to add a spring connection. If you do that, set Model Validation for Restart Run to No. Otherwise, the solution will not run.For more information, see Adjusting parameters for the restart run.

8. Right-click the restart run solution and choose Edit.

9. In the Solution dialog box, on the Restart Management page, set the following options:Note: The end time of the restart subcase must be later than the time step that is saved in the initial run results for this subcase.From the Generate Restart Data list, select Yes. From the Restart Option list, select Yes.Click Browse to navigate to the .op2 file from the initial run.From the Restart Subcase list, select the ID of the subcase that did not converge in the initial run results. From the Execute Subcase list, select Restart Subcase ID. This ensures that the subcase that did not converge in the initial run will be solved again with the initial results and with any updated solution parameters.

10. Right-click the restart run solution and choose Solve.

11. Repeat steps 4 through 10 until the solution converges.

How do I

Generate results to reuse with different analyses (external restart)

Restart a nonlinear solution (internal restart) (SOL 402)

Learn more

Restarting

External restarts

Internal restarts (SOL 402)

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Troubleshoot convergence (external restart), Simcenter 3D 2021.1 Series

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