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# How to use results from 1st simulation as initial conditions for 2nd eigenfrequency study in COMSOL

## How to use results from 1st simulation as initial conditions for 2nd eigenfrequency study in COMSOL

(OP)
Dear All,

I am trying to define the dispersion curves of a periodic unit cell in COMSOL Multiphysics with prescribed displacements. I am using two separate studies:
- Study 1: Stationary, with prescribed displacements on the four edges of the unit cell.
- Study 2: Eigenfrequency.
I intend to use the results of Study 1 as initial conditions for Study 2.
I also conducted a different eigenfrequency study of the same unit cell, and the dispersion curves from Study 2 and this separate study are similar. This suggests that the results from Study 1 may not have been used as initial conditions for Study 2.
The following figures illustrate my setup. Could I be missing any setup errors?

Displacement on left edge:
Displacement on right edge:
Displacement on top edge:
Displacement on bottom edge:
Study 1 (Stationary) setup: I turn off Floquet-periodic BCs in study 1)
Deformed shape of the unit cell from Study 1:
Floquet-periodic BCs along x direction:
Floquet-periodic BCs along z direction:
Study 2(Eigenfrequency) setup:
Study 2 setup (Turn off "Solved for" of study 1):
Dispersion curves from Study 2:
An eigenmode from Study 2:
A different eigenfrequency study(without prescribed displacements) set up:
Dispersion curves from the different eigenfrequency study:
An eigenmode the different eigenfrequency study:
Replies continue below

### RE: How to use results from 1st simulation as initial conditions for 2nd eigenfrequency study in COMSOL

Well, I worked in FEA and modal analysis for 15 years, and can honestly say I haven't got the faintest idea what you are on about.

Cheers

Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

### RE: How to use results from 1st simulation as initial conditions for 2nd eigenfrequency study in COMSOL

(OP)
Hi GregLocock,

Thank you for your comment. I am a new newcomer. I have updated my problem, please consider it.

Best wishes,
Binh

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