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Complex Band Strucutre - Acoustics/Structural Mechanics

Posted 4 feb 2014, 12:03 GMT-5 Acoustics & Vibrations, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers, Structural Mechanics Version 4.4 1 Reply

Chris Layman
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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 feb 2015, 13:49 GMT-5
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Hello Chris Layman

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Karwan Rostem
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Posted: 10 years ago 2 feb 2015, 13:49 GMT-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

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