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Global Equations defined variable has singular matrix problem?

Dear support,

Does anyone ever meet the following error when using global equations to define a variable as source? I am trying to simulate in 4.3a the enclosed volume of fluid following the COMSOL Blog: www.comsol.com/blogs/computing-controlling-volume-cavity/
Following the guideline in this blog, I can simulate incompressible fluid by using global equations to define the inner pressure in 2D, but the error comes out when I translated it into a 3D model.

Could anyone please give some hint on possible reason? Thanks.

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Failed to find a solution.
Singular matrix.

There are 1 void equations (empty rows in matrix) for the variable comp1.Inner_pressure.
at coordinates: (0,0,0), ...
Returned solution is not converged.
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0 Replies Last Post Mar 31, 2014, 6:00 PM EDT
COMSOL Moderator

Hello Shuai Ge

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