Learning Forum

[Davide Parlato]

Hi everyone, 

I am running a two-way Fluent-Mechanical simulation of a plate(100x3x200mm; xyz) immersed in a tank (300x500x300mm; xyz) filled with a liquid and a gas using VOF method. The tank is subject to the force of gravity. I am having a hard time in reaching the convergence of the displacement on the Coupling Interface, the plate, (see screenshot below) which means endless simulations.
Actually I would like to understand better what I am dealing with. The convergence is related to the RMS change, which basically is telling me how much the variable is changing between two iterations. Why is the force reaching convergence so easily on the coupling interface and the displacement keeps changing? Is it related to Fluent or Mechanical setup, to the time-step chosen, to the mesh? I have tried to read the SC User's Guide but it doesn't help me so much.

Can anyone clarify me this point and/or give me a solution?
Feel free to ask any other information that you may need. Thanks in advance. 

 

[Tasos Zacharakis]

Hello Davide,

If you're encountering an issue where the system coupling has not yet converged, it could be due to a variety of factors.

One common cause is that the solution is not yet fully converged. Check this link : Error: update failed for the solution component in system coupling. The coupled update for system fluid flow (fluent) threw an exception. Update solution failed - Ansys Knowledge.

Another potential issue could be related to the stability of your FSI or 6DOF case. This link : How can I converge an unstable FSI or 6DOF case in Fluent - Ansys Knowledge, provides a comprehensive guide on how to use Fluent's Solution Stabilization for an FSI case or a 6DOF case. It includes information on how to identify instability, how to use solution stabilization, and how to adjust settings for optimal results.

I hope these guidelines will help you with your project.

Thank you,

Tasos