Equilibrium Discharge Model Not Converging

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Hi, I am running a case for Equilibrium Discharge model with convergence criteria (1e-5). I am trying to simulate a thermal plasma torch. But model is not converging and has residual value is fluctuating around 0.1 for each iteration. Also, my temp/velocity profiles(results while solving) are also not changing and have attained a certain profile after 30-40 iterations. Could anyone please suggest a technique to get the model converged. I am attaching a picture of convergence graph for your reference. Thanks in advance.



1 Reply Last Post Apr 16, 2021, 5:19 PM EDT
Robert Koslover Antennas, Waveguides, Electromagnetics

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Posted: 4 weeks ago Apr 16, 2021, 5:19 PM EDT
Updated: 4 weeks ago Apr 16, 2021, 5:23 PM EDT

I can't speak to the particulars of your model. But if you haven't already, take a good look at your mesh quality statistics and see if you can remesh the problem in a manner that improves the mesh quality, especially if/where it is low. Also, consider using a finer mesh, especially where there may be strong gradients in computed quantities. Also, consider a different element discretization (e.g., if presently linear, consider quadratic). Also, consider trying a different solver or different pre-conditioner. Recheck all your boundary and initial conditions to be sure they make sense everywhere. If none of that works, consider posting your model to the forum. There's always a chance someone here will find a way to fix it. :) See also: https://www.comsol.com/support/knowledgebase/1260 and https://www.comsol.com/support/knowledgebase/103 or just search the Comsol Knowledge Base for "convergence" and follow the links.

I can't speak to the particulars of your model. But if you haven't already, take a good look at your mesh quality statistics and see if you can remesh the problem in a manner that improves the mesh quality, especially if/where it is low. Also, consider using a finer mesh, especially where there may be strong gradients in computed quantities. Also, consider a different element discretization (e.g., if presently linear, consider quadratic). Also, consider trying a different solver or different pre-conditioner. Recheck all your boundary and initial conditions to be sure they make sense everywhere. If none of that works, consider posting your model to the forum. There's always a chance someone here will find a way to fix it. :) See also: https://www.comsol.com/support/knowledgebase/1260 and https://www.comsol.com/support/knowledgebase/103 or just search the Comsol Knowledge Base for "convergence" and follow the links.

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