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Laser heating time dependent study doesn't change with time.

Posted 25.07.2019, 11:38 GMT-4 Heat Transfer & Phase Change, Studies & Solvers Version 5.4 2 Replies

Mathieu Moras
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Hi,

I'm kind of new to COMSOL and I'm trying to model the laser induced heating of a silicon wafer. I've looked at the laser heating tutorial given by COMSOL but I'm more interested in the conduction along the depth of the wafer not the surface distribution. I'm modeling a phase change in the silicon with the absortion coefficient that suddenly goes up really fast as we reach the melting temperature and stays constant past it.

The pulsed laser is modeled by a heat source at the surface z=0 that is gaussian in the xy plane, follows the beer-lambert law along the z axis and it's power is gaussian in time (1 pulse).

I know from experiments that the temperature should rise pretty high but it barely changes if not at all. I have tried to change the mesh, the boundary boundary conditions but nothing seems to work.

I've attached the file.

Thank you.

Attachments:

2 Replies Last Post 29.07.2019, 11:01 GMT-4
Julian Anaya
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Posted: 5 years ago 29.07.2019, 05:54 GMT-4
Updated: 5 years ago 29.07.2019, 08:20 GMT-4

Dear Mathieu,

There are couple of mistakes in your model. You have a very fast pulse and your mesh can not capture it (think on the diffusion legth in your material). For this problem you need to add a boundary layer to solve that. The other problem is that the time dep solver cannot capture your pulse. You have an automatic timestep conf in the solver, so you either need to add either an event to capture the beggin of the pulse or change the timestep in the solver to control the times tighter. I've added some mods to your model and temperatues are indeed rather high...

Kind regards,

Julian

Dear Mathieu, There are couple of mistakes in your model. You have a very fast pulse and your mesh can not capture it (think on the diffusion legth in your material). For this problem you need to add a boundary layer to solve that. The other problem is that the time dep solver cannot capture your pulse. You have an automatic timestep conf in the solver, so you either need to add either an event to capture the beggin of the pulse or change the timestep in the solver to control the times tighter. I've added some mods to your model and temperatues are indeed rather high... Kind regards, Julian
Mathieu Moras
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Posted: 5 years ago 29.07.2019, 11:01 GMT-4
Updated: 5 years ago 29.07.2019, 10:50 GMT-4

I added a boundary layer and an event to my model and it seems to produce much better result! I will keep looking further into these features.

Thank you very much.

I added a boundary layer and an event to my model and it seems to produce much better result! I will keep looking further into these features. Thank you very much.

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