Thanks for your response. I checked the solver, it is using fully coupled direct solver by default. I’ve tried to ramp up the load to eliminate any large nonlinear problem, but it is not fixed still. I’ll contact the support. Followed is the thread link I posted with the model file attached, only if you could take a look. Thanks a lot!

Best,

Shuai

http://www.comsol.com/community/forums/general/thread/43551/

The issue here is likely that you would want to use a fully coupled direct solver, for the reasons outlined here:

http://www.comsol.com/blogs/improving-convergence-multiphysics-problems/

If this does not address the issue, you should contact the COMSOL Support Team. ]]>

Thanks for posting this thread. It is very helpful for my simulation work. Following the guidelines, I did the simulation of incompressible fluid successfully in 2D with COMSOL4.2a. But when I try to translate this technique into 3D model, I get the following error. Will you have any suggestions on my debugging process? Thanks a lot!

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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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