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Reducing simulation time with two different time steps

Posted Apr 16, 2020, 4:54 a.m. EDT Heat Transfer & Phase Change, Heat Transfer, Studies & Solvers Version 5.3 3 Replies

Marcel Jung
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Hello together,

I would like to simulate the temperature profile during laser drilling with an ultra short pulse laser. The problem is that the pulse duration is 800 fs, but the drilling takes 0.1 s. If my time step is greater than 1e-11 s, the pulse is not recognized by the software. If the time step is 1e-11s and the endtime is 0.1 s the simulation time is much too long.

Is there a possibility to shorten the simulation time, but the pulse is still detected?

Thanks for the help Best regards Marcel Jung

3 Replies Last Post Apr 17, 2020, 4:18 a.m. EDT
Edgar J. Kaiser Certified Consultant
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Posted: 5 years ago Apr 16, 2020, 3:43 p.m. EDT

Marcel,

I think you could use two subsequent time dependent steps. A first one with small time steps to resolve the laser pulse and a second one with longer time steps for the rest. Take the final result of the first time dependent step as initial condition for the second.

Cheers Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Marcel, I think you could use two subsequent time dependent steps. A first one with small time steps to resolve the laser pulse and a second one with longer time steps for the rest. Take the final result of the first time dependent step as initial condition for the second. Cheers Edgar
Marcel Jung
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Posted: 5 years ago Apr 17, 2020, 3:41 a.m. EDT

Hello Edgar,

Thank you for your prompt reply. I've already tried two time steps. The problem is that I have to look at the laser pulse for 0.1 s and during this time I cannot currently use any longer time steps because the pulse is then no longer recognized. For the cooling phase after drilling, I agree to work with different time steps. My problem is only the 0.1 s for the hole.

Best regards Marcel

Hello Edgar, Thank you for your prompt reply. I've already tried two time steps. The problem is that I have to look at the laser pulse for 0.1 s and during this time I cannot currently use any longer time steps because the pulse is then no longer recognized. For the cooling phase after drilling, I agree to work with different time steps. My problem is only the 0.1 s for the hole. Best regards Marcel
Friedrich Maier COMSOL Employee

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Posted: 5 years ago Apr 17, 2020, 4:18 a.m. EDT
Updated: 5 years ago Apr 17, 2020, 4:20 a.m. EDT

Dear Marcel,

there are varous possibilites you can try to control such models.

1: Use two study steps in your study. The first time dependent step with a small time resolution to capture the laser pulse and the second time dependent step with larger time stepping to capture the heat transfer

2: You can enter several sequential ranges e.g. range(0,0.001,.01) range(.02,.01,.1) in your times settings intervals. Please note that it could be important to control the time stepping: https://www.comsol.com/support/knowledgebase/1254

3: You can benefit from the events interface. https://www.comsol.com/support/knowledgebase/1245

Finally, if you have access to a COMSOL Multiphysics license under subscription please do not hesitate to contact the comsol support for such questions: https://www.comsol.de/support

Kind regards Friedrich

Dear Marcel, there are varous possibilites you can try to control such models. 1: Use two study steps in your study. The first time dependent step with a small time resolution to capture the laser pulse and the second time dependent step with larger time stepping to capture the heat transfer 2: You can enter several sequential ranges e.g. range(0,0.001,.01) range(.02,.01,.1) in your times settings intervals. Please note that it could be important to control the time stepping: https://www.comsol.com/support/knowledgebase/1254 3: You can benefit from the events interface. https://www.comsol.com/support/knowledgebase/1245 Finally, if you have access to a COMSOL Multiphysics license under subscription please do not hesitate to contact the comsol support for such questions: https://www.comsol.de/support Kind regards Friedrich

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.

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