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Problem in Global Equations defined variable

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Hi all,

Does anybody know how to fix this? I am simulating a cavity filled with incompressible fluid under external pressure. Following the COMSOL Blog: www.comsol.com/blogs/computing-controlling-volume-cavity/, I used the global equations to define a pressure load "Inner_pressure" to the inner wall of a cavity beam. The global equation is set to find out whatever value of "Inner_pressure" only if it can satisfy the constraint that the cavity's volume is always the same to undeformed state. I tried this method in 2D successfully, but in 3D it has a error like this.

****************************************
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.
****************************************


2 Replies Last Post Jun 27, 2017, 2:46 p.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 1 decade ago Apr 10, 2014, 1:21 a.m. EDT
Hi,

In order to compute the volume using the technique from the blog post, the study must be geometrically nonlinear. It is only then that the spatial coordinates reflect the deformed configuration.

Regards,
Henrik
Hi, In order to compute the volume using the technique from the blog post, the study must be geometrically nonlinear. It is only then that the spatial coordinates reflect the deformed configuration. Regards, Henrik

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Posted: 7 years ago Jun 27, 2017, 2:46 p.m. EDT
Updated: 7 years ago Jun 27, 2017, 2:46 p.m. EDT
Link above is "broken" since it includes comma

Working link is below

www.comsol.com/blogs/computing-controlling-volume-cavity/

Link above is "broken" since it includes comma Working link is below https://www.comsol.com/blogs/computing-controlling-volume-cavity/

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