Menu

Discussion Forum

New Discussion
Filter

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Could I use a COMSOL eigenfrequency mode result as initial value of a time dependent simulation?

Posted Nov 13, 2016, 4:48 a.m. EST MEMS & Nanotechnology, Acoustics & Vibrations, MEMS & Piezoelectric Devices, Structural Mechanics Version 4.3a 2 Replies

Qi Zhang
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

I want to calculate strain energy of a system, say a single beam, with deformation being coupling of two modes. Taking single beam system with dimension 1*1*100 um as an example, set the two ends of the are fixed and we will find all mechanical eigenmodes (shapes are sinusoidal) by eigenfrequency study in structural mechanics. Now i am trying to calculate total strain energy of the beam when the beam is deformed in shape of the superposition of first two modes with coefficients q1 and q2 respectively. One way to realize this is that output the shape of the first two modes and sum the shapes multiplying by q1 and q2 respectively, then input the result as a initial value in a time dependent study.
Can this be done?
P. S. Apparently the two studies should be in same mesh.
P. S. 2 Now I can output the mode shape as a .txt document, but this may not be able input to comsol again.
2 Replies Last Post Nov 16, 2016, 9:49 p.m. EST
Henrik Sönnerlind COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 8 years ago Nov 14, 2016, 7:42 a.m. EST
Hi,

You could use an expression like

q1*withsol('sol2',u,setind(lambda,1))+q2*withsol('sol2',u,setind(lambda,2))

Regards,
Henrik
Hi, You could use an expression like q1*withsol('sol2',u,setind(lambda,1))+q2*withsol('sol2',u,setind(lambda,2)) Regards, Henrik
Qi Zhang
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 8 years ago Nov 16, 2016, 9:49 p.m. EST
Thank you very much for your reply!

But I still cannot get it to work. It seems that the withsol operator comes from version 5.1 of COMSOL, but what I am using is version 4.3a. Are there any alternative method to do this?

Thanks very much in advance.
ZHANG, Qi
Thank you very much for your reply! But I still cannot get it to work. It seems that the withsol operator comes from version 5.1 of COMSOL, but what I am using is version 4.3a. Are there any alternative method to do this? Thanks very much in advance. ZHANG, Qi

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content