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Simple Joule heating simulation error

Posted Mar 19, 2018, 11:13 a.m. EDT Electromagnetics, Heat Transfer & Phase Change, Studies & Solvers Version 5.3 2 Replies

Sami Hawasli
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Hello, I am trying to follow along with the COMSOL example about joule heating, but i am running into some errors. I want to create a very simple simulation, a metal coil on a diamond substrate. I am neglecting any convection or radiation effects at the moment, I only want to calculate the temperate of the coil at specific input voltages. I am currently running into an error that I cannot understand / solve. “Failed to find a solution. Segregated Step 1 Singular matrix. There are 223100 void equations (empty rows in matrix) for the variable comp1.V. at coordinates: (-0.000125,-0.000115461,-1.99682e-005), (-0.000125,-0.000116172,-1.49198e-005), (-0.000125,-0.000116884,-9.87132e-006), (-0.000125,-0.00012023,-1.67341e-005), (-0.000125,-0.000120942,-1.16857e-005), ... and similarly for the degrees of freedom (empty columns in matrix). In Segregated Step 1: Returned solution is not converged.”

I have a feeling I have set up my simulation incorrectly. Any help or advice would be great! Thank you in advance, Sami

2 Replies Last Post Mar 19, 2018, 12:03 p.m. EDT
Edgar J. Kaiser Certified Consultant
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Posted: 6 years ago Mar 19, 2018, 11:55 a.m. EDT

Sami,

the problem is in the small domain where ground and the electric potential BCs are assigned. The geometry is not clean there. You can also observe that in the mesh.

Cheers Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Sami, the problem is in the small domain where ground and the electric potential BCs are assigned. The geometry is not clean there. You can also observe that in the mesh. Cheers Edgar
Magnus Ringh COMSOL Employee

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Posted: 6 years ago Mar 19, 2018, 12:03 p.m. EDT

Hi Sami,

The reason for the error is that the electrical conductivity for the Diamond and Air materials is zero, which creates a singular matrix. Set those conductivities to a small nonzero value instead. The model then converges, but the solution does not seem to contain any Joule heating. You also have an Electric Potential node with a 0 potential (that is, ground) so the model does not "produce" any electric current. Setting the electric potential to a nonzero value results in a more interesting solution.

Best regards, Magnus Ringh, COMSOL

Hi Sami, The reason for the error is that the electrical conductivity for the Diamond and Air materials is zero, which creates a singular matrix. Set those conductivities to a small nonzero value instead. The model then converges, but the solution does not seem to contain any Joule heating. You also have an Electric Potential node with a 0 potential (that is, ground) so the model does not "produce" any electric current. Setting the electric potential to a nonzero value results in a more interesting solution. Best regards, Magnus Ringh, COMSOL

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