Why the `Null` matrix extracted from the COMSOL 'beam-solid coupling' model (or any other model with beam) through MATLAB API has non-zero and non-one elements,

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In my study I build a structural model contains a beam and a solid, and I need to extract the dynamics model through the MATLAB API, the code is as follows

MA = mphmatrix(model ,'sol3', 'Out', {'K','D','E','Null','Nullf','ud','uscale'},'initmethod','sol','initsol','zero');

where sol3 is Transient study. However, the Null matrix which describes constraints information has non-zero and non-one elements, and these elements are corresponding to the beam elements. Is this type of Null matrix right ? Part of the Null matrix is shown as follows:

0 0 0 0
-0.0184870106390901 0.00777682556585971 0 0
-0.0220925147574181 0 0.00777682556585971 0
0 0 0 0.0830223122472619

0 Replies Last Post 14 oct. 2024, 03:04 UTC−4
COMSOL Moderator

Hello Cong Shen

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