How to Enable the Restart Option for a Transient Fluid-Thermal-Mechanical Simulation using System Coupling Standalone

System Coupling Challenges

Most of us have faced an engineering problem in which we required a thermal-structural transient analysis coupled with a fluid flow transient analysis. We set up our case in Ansys Workbench, we run our case, but then when we want to restart the simulation, a warning message shows up telling us that “Not all participants support restarted runs.” From this point, the only thing we can do is restart the simulation all over again.

In Ansys Workbench, System Coupling does not support restarting a coupled analysis when a steady-state or transient thermal analysis is included (https://ansyshelp.ansys.com/public/account/secured?returnurl=/Views/Secured/corp/v252/en/sysc_ug/sysc_ovr_restart_restarting.html?q=restart). As a result, restarting the simulation directly within Workbench is not possible. However, you can enable restart functionality by exporting your setup and running the simulation through Ansys System Coupling in Standalone mode.

This blog details the process for adapting a System Coupling setup created in ANSYS Workbench so it can be exported and executed using the standalone System Coupling interface. By doing so, you benefit from Workbench’s streamlined environment for building coupled thermal-mechanical analyses while enabling restart capabilities not available within Workbench itself. The primary objective is to adjust configurations for ongoing simulations, allowing for efficient restarts without replicating the setup from the beginning.

System Coupling Configuration

The step-by-step workflow presented here is applicable to any System Coupling configuration involving thermal-mechanical analysis. For illustration, the procedure will reference the setup depicted in the following image throughout this guide.

1. First, make a copy of your workbench case, so you do not lose information.
2. In the system coupling cell configuration, navigate to Execution Control and set the Intermediate Restart Data Output to either a defined step interval or to output all steps. This can also be modified later when working in the System Coupling standalone environment.
   
   
3. Now go to Solution, right-click, and reset it.
   
   
4. Close your system coupling window and open your mechanical case setup.
5. In Mechanical, add a commands task and then add the code as shown in the image.
      
   
   
   
6. After that, click on the coupled field transient analysis, and go to the configuration windows. There, look for Analysis data management, and in the Delete Unneeded Files set it as No.
   
   
7. Next, right-click on the coupled field transient analysis and select Write System Coupling Files. Store these files in a newly created folder that will contain all simulation results and coupling data, using clear and descriptive filenames for easy reference.
   
   
   
   
8. Save the project (You can close the mechanical window).
   
9. In the Ansys Workbench desktop, right-click on the setup cell of mechanical analysis and update it.
   
   
   
   
10. Now, open the system coupling setup again and click on yes to reread upstream data.
    
    
    
    
11. Close the system coupling window.
12. Export the system coupling setup by right-clicking on the setup cell and selecting Export System Coupling Setup. Save the files in the same folder where the mechanical files were saved in step 7.
    
    
    
    
13. Open the system coupling standalone version, and as a working path, select the folder created in step 7.
14. Ansys System Coupling will open all the system coupling configurations. After it finishes uploading all the files, go to solution control and set the new End time.
    
    
15. Start the coupled simulation.
16. If you need to restart your simulation later, you need to go first to File and click on Open at Step. Select the latest simulation time or the time step you want to restart. Then, you can start the simulation.

Ansys Solution Benefits

Ansys is a powerful platform for multi-physics simulations, making it especially effective for system coupling analyses that involve thermal, structural, and fluid interactions. Its industry-leading solvers, Fluent for fluid flow and heat transfer, and Mechanical for structural and thermal analysis, can be seamlessly integrated through System Coupling, allowing engineers to simulate complex, interdependent physical phenomena with high accuracy. To further enhance simulation workflows, Ansys provides advanced tools like DesignXplorer and OptiSLang, which support parametric studies, sensitivity analysis, and design optimization. These tools enable engineers to explore design variations efficiently and make data-driven decisions early in the development process. Altogether, Ansys delivers a robust and scalable environment for multi-physics modeling, helping teams reduce development time, improve product performance, and increase confidence in simulation results.

Ozen Engineering expertise

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Suggested Blogs:

• https://blog.ozeninc.com/resources/2-way-coupling-with-fluent-and-rocky-applications-in-water-treatment
• https://blog.ozeninc.com/resources/one-way-vs.-two-way-coupling-busbar-thermal-analysis-in-ansys-maxwell-icepak