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How to correctly calculate the eigenvalues of the stiffness matrix in COMSOL
Posted 12.10.2020, 23:15 GMT-4 Structural & Acoustics, Acoustics & Vibrations, Studies & Solvers Version 5.4 0 Replies
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Hi,
Recently, i had a puzzle about the mechanism of COMSOL to calculate the eigenvalues. So, i've made a test with 5 nodes linear mesh in acoutic module.
Firstly, i exported the stiffness matrix and mass matrix in matlab, with the code 'STR=mphmatrix(model,'sol1','out',{'K','E'}); K=STR.K; E=STR.E'. Then i caculated its eigenvalues with code 'eigs(K,E,2)', yet the caculated eigenvalues are so different from COMSOL's.
So, i puzzled about my procedure. Are the eigenvalues derived from (K-lambda^2 E)U=0 in COMSOL? How can i get the correct eigenvalues in matlab?
Good luck.
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Hello Jiachen Luo
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