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 The information provided may be out of date.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.

Complex Band Strucutre - Acoustics/Structural Mechanics

Please login with a confirmed email address before reporting spam

Hi

In a typical phononic band structure calculation done within COMSOL the procedure is to define Floquet BC's and do a parametric sweep of the wave vector over a particular direction in the irreducible Brillouin zone. The output are frequencies and the input is wave vector. Simple enough.

However, it is also worthwhile to study the evanescent modes in lossy materials, this is done by calculating the complex band structure (usually done with an extended plane wave expansion procedure). The complex band structure is calculated by using a real frequency as input and solving for complex wave number. Thus resulting in two dispersion curves, one is omega vs real(k) and one is omega vs imag(k). My question is then can this easily be done within COMSOL? Even if someone has done this within the scope of optics or electronics, it would be helpful.

thanks
~Chris

1 Reply Last Post 2 févr. 2015, 13:49 UTC−5
COMSOL Moderator

Hello Chris Layman

Your Discussion has gone 30 days without a reply. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help.

If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base.


Please login with a confirmed email address before reporting spam

Posted: 10 years ago 2 févr. 2015, 13:49 UTC−5
Hello,

I just saw this and thought I might reply, even though the thread is a bit old. I did model the complex band structure for Lamb modes, and I confirmed the answer with a numerical code that I wrote in Matlab. You need to write -1i*K_x etc in the Floquet boundary conditions in order to simulate the exponential decays.

Best,

Karwan
Hello, I just saw this and thought I might reply, even though the thread is a bit old. I did model the complex band structure for Lamb modes, and I confirmed the answer with a numerical code that I wrote in Matlab. You need to write -1i*K_x etc in the Floquet boundary conditions in order to simulate the exponential decays. Best, Karwan

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.