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help with time dependent study: temperature is not changing

Posted Dec 14, 2023, 12:49 p.m. EST Version 6.1 5 Replies

Duanhui Li
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Hi guys,

I am running a very simple model to make sure my time dependent study setting is right. Obviously it's not.... I have set my temperature profile using interpolation as the TC_profile. And the "temperature profile" shows the setting is OK.

I also made sure that the temeprature input for the linear elastic material is using the TC_profile, and the time dependent study time range is OK.

But after I ran the time dependent study, and plot the temperature Vs time, the temperautre seems not changing at all. It's always 233.15K, as shown in the "temperature from time dependent study".

I really don't understand where I did wrong in this.

Could you help take a look in my model?

Thank you!

5 Replies Last Post Dec 15, 2023, 2:45 p.m. EST
Jeff Hiller COMSOL Employee

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Posted: 11 months ago Dec 14, 2023, 5:50 p.m. EST
Updated: 11 months ago Dec 14, 2023, 5:36 p.m. EST

Hello Danhui,

I only took a quick look at your model and I could be wrong, but while I see where TC_profile enters the Solid Mechanics branch of your model, I don't see where it enters the Heat Transfer in Solids branch. If I am correct, there's no reason the temperature (which is the solution of the equation set up by that branch) would change.

Best,

Jeff

PS: If TC_profile is the temperature that you know the entire object is at, then there is no reason to solve for T and no need for a Heat Transfer in Solids branch.

-------------------
Jeff Hiller
Hello Danhui, I only took a quick look at your model and I could be wrong, but while I see where TC_profile enters the Solid Mechanics branch of your model, I don't see where it enters the Heat Transfer in Solids branch. If I am correct, there's no reason the temperature (which is the solution of the equation set up by that branch) would change. Best, Jeff PS: If TC_profile is the temperature that you know the entire object is at, then there is no reason to solve for T and no need for a Heat Transfer in Solids branch.
Duanhui Li
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Posted: 11 months ago Dec 14, 2023, 8:17 p.m. EST
Updated: 11 months ago Dec 14, 2023, 8:03 p.m. EST

Hello Danhui,

I only took a quick look at your model and I could be wrong, but while I see where TC_profile enters the Solid Mechanics branch of your model, I don't see where it enters the Heat Transfer in Solids branch. If I am correct, there's no reason the temperature (which is the solution of the equation set up by that branch) would change.

Best,

Jeff

PS: If TC_profile is the temperature that you know the entire object is at, then there is no reason to solve for T and no need for a Heat Transfer in Solids branch.

Thank you Jeff! You are right. I should add a Temperature 1 to state the temperature setting in the Heat transfer in solids. Once I do that, it works.

I have a follow up question. I agree with you that I should not need to have Heat transfer in Solids. But if I disable the Heat transfer in Solids and the Thermal expansion, and I input the temperature profile in Thermal Expansion and Creep in Linear Elastic Materials 1, the solver will give an error in the Time dependent study. The error said I did not define T. But I did it in the Linear elastic materials. I have uploaded this model and I wonder if you could help point out what is missing in my understanding?

Thank you so much!

>Hello Danhui, > >I only took a quick look at your model and I could be wrong, but while I see where TC_profile enters the Solid Mechanics branch of your model, I don't see where it enters the Heat Transfer in Solids branch. If I am correct, there's no reason the temperature (which is the solution of the equation set up by that branch) would change. > >Best, > >Jeff > >PS: If TC_profile is the temperature that you know the entire object is at, then there is no reason to solve for T and no need for a Heat Transfer in Solids branch. Thank you Jeff! You are right. I should add a Temperature 1 to state the temperature setting in the Heat transfer in solids. Once I do that, it works. I have a follow up question. I agree with you that I should not need to have Heat transfer in Solids. But if I disable the Heat transfer in Solids and the Thermal expansion, and I input the temperature profile in Thermal Expansion and Creep in Linear Elastic Materials 1, the solver will give an error in the Time dependent study. The error said I did not define T. But I did it in the Linear elastic materials. I have uploaded this model and I wonder if you could help point out what is missing in my understanding? Thank you so much!

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Jeff Hiller COMSOL Employee

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Posted: 11 months ago Dec 15, 2023, 8:48 a.m. EST
Updated: 11 months ago Dec 15, 2023, 8:34 a.m. EST

Hello Danhui,

Looks like the error is not from the solver, it's from Plot: Line Graph 1. It makes sense that it would return an error since that plot tries to graph a quantity that you are no longer solving for.

Best,

Jeff

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Jeff Hiller
Hello Danhui, Looks like the error is not from the solver, it's from Plot: Line Graph 1. It makes sense that it would return an error since that plot tries to graph a quantity that you are no longer solving for. Best, Jeff
Duanhui Li
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Posted: 11 months ago Dec 15, 2023, 2:06 p.m. EST
Updated: 11 months ago Dec 15, 2023, 2:05 p.m. EST

Hello Danhui,

Looks like the error is not from the solver, it's from Plot: Line Graph 1. It makes sense that it would return an error since that plot tries to graph a quantity that you are no longer solving for.

Best,

Jeff

Thank you Jeff!

I thought the Linear elastic material carries the temperature. But that does not work for the plot. Now I get it. Appreciate you kind help.

>Hello Danhui, > >Looks like the error is not from the solver, it's from Plot: Line Graph 1. It makes sense that it would return an error since that plot tries to graph a quantity that you are no longer solving for. > >Best, > >Jeff Thank you Jeff! I thought the Linear elastic material carries the temperature. But that does not work for the plot. Now I get it. Appreciate you kind help.
Jeff Hiller COMSOL Employee

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Posted: 11 months ago Dec 15, 2023, 2:45 p.m. EST
Updated: 11 months ago Dec 15, 2023, 2:31 p.m. EST

The Linear Elastic Material node "knows" the temperature as TC_profile(t), whereas your plot is of T. If you want to plot the temperature, you can edit the Plot Line Graph 1 so that it plots TC_profile(t) instead of T, and the error message goes away. Then again, you can plot TC_profile straight from the node where you define it, without having to solve the equations (I mention this in case you are plotting it just to check that it looks as you want it to).

Best,

Jeff

-------------------
Jeff Hiller
The Linear Elastic Material node "knows" the temperature as TC_profile(t), whereas your plot is of T. If you want to plot the temperature, you can edit the Plot Line Graph 1 so that it plots TC_profile(t) instead of T, and the error message goes away. Then again, you can plot TC_profile straight from the node where you define it, without having to solve the equations (I mention this in case you are plotting it just to check that it looks as you want it to). Best, Jeff

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