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 The information provided may be out of date.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.

Heat distribution of an infrared focused laser beam

Please login with a confirmed email address before reporting spam

Hi all,

I am looking to model the localized heating of a focused infrared beam. In specific I am looking to model a 1064nm optical trap, given the absorption of the trapping medium and the power of the beam.

The assumption I make is that all absorption events are dissipated through heat which is likely reasonable at these frequencies. I would also like to make this a transient model in the future, however I am suffering from fundamental problems.

I model the intensity profile of the beam, which seems to work out well. However when I couple the absorption (attenuation) coefficient as the heat induced I am encountered with non-physical temperatures.

Am i missing something simple or is my assumption just fundamentally wrong?

Thanks in advance
Jakrey Myers


2 Replies Last Post 10 mai 2012, 03:27 UTC−4

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 10 mai 2012, 03:10 UTC−4
After realizing COMSOL not liking my wz parameter expression I created an analytical version and was confronted with some new errors.

File attached

Thanks in advance
Jakrey
After realizing COMSOL not liking my wz parameter expression I created an analytical version and was confronted with some new errors. File attached Thanks in advance Jakrey


Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 10 mai 2012, 03:27 UTC−4
Hi

first of all your wz is not a parameter, but a variable, remove it from the "parameter" section and add a Definition variable
and add it therein.

Then I'm astonished from the heat flux shape, if you add a 2D plot, Surface plot with the ht.Qtot COMSOL variable, then turn on wireframe and add a height Expression subnode, you will see that you deposit your energy really only over a few mesh elements, either you have a typo in your formula, or you need to encircle that region and use a much finer mesh therearound, and use a coarser one outside.

It is often usefull to set such formulas as for your heat flux into an anlalytical expression as you can then easily plot it and check that its coherent with your wish

--
Good luck
Ivar
Hi first of all your wz is not a parameter, but a variable, remove it from the "parameter" section and add a Definition variable and add it therein. Then I'm astonished from the heat flux shape, if you add a 2D plot, Surface plot with the ht.Qtot COMSOL variable, then turn on wireframe and add a height Expression subnode, you will see that you deposit your energy really only over a few mesh elements, either you have a typo in your formula, or you need to encircle that region and use a much finer mesh therearound, and use a coarser one outside. It is often usefull to set such formulas as for your heat flux into an anlalytical expression as you can then easily plot it and check that its coherent with your wish -- Good luck Ivar

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.