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How to correctly calculate the eigenvalues of the stiffness matrix in COMSOL

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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.



0 Replies Last Post 12.10.2020, 23:15 GMT-4
COMSOL Moderator

Hello Jiachen Luo

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