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Time step in time dependent study

Posted 24 mag 2023, 08:15 GMT-4 Structural & Acoustics, Acoustics & Vibrations Version 5.6 2 Replies

Himanshu Gupta
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Hi, I am very new to COMSOL or any kind of FEM simulation software.

I need a very fine time step to solve a structural dynamics - wave propagation problem in time domain. It is computing with range(0,1e-8,1), but when I go for range(0,1e-9,1) it says, "OUT OF MEMORY" Is this problem related to my system or it is a limitation of COMSOL?

I am using i7-12700K 4.46 GHz CPU with 32 GB RAM. What are the possible solution to this? Kindly help.

Thanks & Regards

2 Replies Last Post 24 mag 2023, 13:18 GMT-4
Dave Greve
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Posted: 2 years ago 24 mag 2023, 12:03 GMT-4

By default Comsol stores the solution at each time step, where the "solution" means u,v,w for each mesh element.

I think you will find that 1E9 multiplied by the number of mesh elements multiplied by 3 is more than your hard disk size.

I suggest you explain what you are trying to do, post your model, and ask for suggestions.

By the way expecting that a time-dependent solution will neither diverge or see numerical damping for > 1e9 iterations is...very optimistic.

By default Comsol stores the solution at each time step, where the "solution" means u,v,w for each mesh element. I think you will find that 1E9 multiplied by the number of mesh elements multiplied by 3 is more than your hard disk size. I suggest you explain what you are trying to do, post your model, and ask for suggestions. By the way expecting that a time-dependent solution will neither diverge or see numerical damping for > 1e9 iterations is...very optimistic.
Jeff Hiller COMSOL Employee

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Posted: 2 years ago 24 mag 2023, 13:18 GMT-4

Hello Himanshu,

To add a bit to Dave's post, you can read more on this topic in this blog post which discusses how time steps are selected by the software by default, and what options you have to override that default behavior.

Jeff

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Jeff Hiller
Hello Himanshu, To add a bit to Dave's post, you can read more on this topic in [this blog post](https://www.comsol.com/blogs/automatic-time-step-and-order-selection-in-time-dependent-problems/) which discusses how time steps are selected by the software by default, and what options you have to override that default behavior. Jeff

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