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error:singular matrix

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When i try to compute a stationary problem of a 3d model,singular matrix occurs,like: - Feature: Stationary Solver 1 (sol2/s1) Failed to find a solution. Singular matrix.

For mesh-case 0 there are 29578 void equations (empty rows in matrix) for the variable comp1.V. at coordinates: (-0.04,-0.04,-0.04), (-0.04,-0.032,-0.04), (-0.04,-0.036,-0.04), (-0.036,-0.04,-0.04), (-0.032,-0.04,-0.04), ... and similarly for the degrees of freedom (empty columns in matrix). Returned solution is not converged. Not all parameter steps returned. i find one of my material,air,has a 0 conductivity(default).then i change it to a tiny value,like 1,the singular matrix problem disappears.


1 Reply Last Post Apr 1, 2020, 8:00 a.m. EDT
Lars Dammann COMSOL Employee

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Posted: 4 years ago Apr 1, 2020, 8:00 a.m. EDT

Hi, changing the conductivity to a small, finite value is indeed a very common fix for this problem. This is usually not a big problem for most models as the error by the tiny conductivity should be negligible. You can make some models work with exactly 0 conductivity by adding/removing gauge-fixing or by using a different interface. This depends on your model, though. I could give more specific advice if you could post your model here. Best regards, Lars

Hi, changing the conductivity to a small, finite value is indeed a very common fix for this problem. This is usually not a big problem for most models as the error by the tiny conductivity should be negligible. You can make some models work with exactly 0 conductivity by adding/removing gauge-fixing or by using a different interface. This depends on your model, though. I could give more specific advice if you could post your model here. Best regards, Lars

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