Why is my COMSOL solution not converging?

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Discussion Overview

The discussion revolves around issues related to solution convergence in COMSOL, specifically when using the incompressible Navier-Stokes model. Participants share their experiences and troubleshooting steps regarding error messages encountered during simulations.

Discussion Character

  • Technical explanation, Homework-related

Main Points Raised

  • Yael describes encountering a convergence error in COMSOL related to the incompressible Navier-Stokes model, specifically a message indicating that the relative error exceeds the tolerance.
  • One participant suggests that there is a known issue with pressure calculations in the Navier-Stokes physics and recommends unchecking "p" on the "Solve for" card in the Solver Parameters.
  • Yael expresses confusion about the location of the "Solve for" option and requests clarification on the specific solver being used.
  • A later reply clarifies that the option is found in the Solver Manager.
  • Yael confirms that following the advice resolves the convergence issue.

Areas of Agreement / Disagreement

Participants generally agree on the troubleshooting steps for resolving the convergence issue, with one participant providing a solution that is later confirmed to be effective. However, there is no broader consensus on the underlying causes of the convergence problems.

Contextual Notes

Some assumptions about the specific settings and configurations in COMSOL may not be fully detailed, and the discussion does not explore all potential causes for convergence issues.

Who May Find This Useful

This discussion may be useful for students and users of COMSOL who are experiencing similar convergence issues with the incompressible Navier-Stokes model.

yaelgo
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Hello,
I'm a 2nd year student, and I'm trying to get to know COMSOL. I'm starting off by solving simple problems with the incompressible Navier-Stokes model, but I keep having trouble with the convegence of the solution.
I keep getting the following error:

"Failed to find a solution:
The relative error is greater than the relative tolerance.
Returned solution has not converged."

I've tried to solve many problems, but it gives me the same error over and over again.
I've changed the number of iterations, the tolerance and the DOF by remeshing, but nothing seems to help.


If someone here has a usefull advice, I would really appreciate it.

Thanks,
Yael.
 
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I had the same problem. Comsol has a problem with pressure calculations in Navier-Stokes physics. You have to uncheck "p" on "Solve for" card in Solver Parameters.
 
Thank you!
but I don't really understand what you mean - I can't see "solve for" in the solver parameters.
could you be more specific? what solver are you using?

Thanks,
Yael.
 
Sorry, my fault - it's in Solver Manager.
 
it works! thanks :)
 

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