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Convergence issues with 2D DC discharge in Plasma module

Posted Apr 11, 2020, 6:43 p.m. EDT Electromagnetics, Plasma Physics, Fluid & Heat Version 5.5 2 Replies

Malik M Tahiyat Plasma Physics and Chemistry
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I am trying to model a 2D DC dishcarge in nitrogen with an external circuit.

I tried both by using an external circuit physics and using the COMSOL's inbuilt series RC circuit.

I could not make much headaway witht he inbuit COMSOL circuit but while using an external circuit, I was able to start the simulation running. But I coudl not get the soution to converge.

Most frequent errors I ha gooten previously was "failed to find consistent initial values" which seemed mostly from mesh issues.

The model is attached.

I have tried numerous attempts in fining and coarsing my mesh as well as shortening the time-step. But could not seem to do better.

WIll greatly appreciate if someoen could take a look at this and suggest directions of approach.

-------------------
Thanking you,
-Malik M Tahiyat
Graduate Research Assistant,
Department of Mechanical Engineering
University of South Carolina (USC)
300 Main Street, Room A 137
Phone: +1(803)-318-0274
2 Replies Last Post Apr 13, 2020, 5:45 p.m. EDT
Edgar J. Kaiser Certified Consultant
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Posted: 5 years ago Apr 12, 2020, 12:00 p.m. EDT

Malik,

we don't have the plasma module, so can't say anything about the physics settings. But in many cases the time dependent step needs a stationary step before, that provides the initial values. Another option is to ramp up the boundary conditions slowly from 0 to the setpoint.

Cheers Edgar

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Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Malik, we don't have the plasma module, so can't say anything about the physics settings. But in many cases the time dependent step needs a stationary step before, that provides the initial values. Another option is to ramp up the boundary conditions slowly from 0 to the setpoint. Cheers Edgar
Malik M Tahiyat Plasma Physics and Chemistry
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Posted: 5 years ago Apr 13, 2020, 5:45 p.m. EDT

Edgar,

Thank you very much for your reply.

Can you procide instructions how to include the stationary step and how to ramp up the boundary conditions?

That would be very helpful.

-------------------
Thanking you,
-Malik M Tahiyat
Graduate Research Assistant,
Department of Mechanical Engineering
University of South Carolina (USC)
300 Main Street, Room A 137
Phone: +1(803)-318-0274
Edgar, Thank you very much for your reply. Can you procide instructions how to include the stationary step and how to ramp up the boundary conditions? That would be very helpful.

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