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multiphysics couplings

Posted 11 mai 2011, 09:41 UTC−4 Fluid & Heat, Heat Transfer & Phase Change Version 4.1 6 Replies

Ting Yan
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Hi everyone,

I have a question about multiphysics couplings.

Now I am doing a water cooling project and I need 2 physics fields: (1)heat transfer in both solids and fluid;(2) laminar flow .

After reading the users guide(P638), I see there is an example "with a Heat Transfer (ht) interface for heat transfer in fluids and a Laminar Flow (spf) interface, you can select Velocity field (spf/fp1), which the Fluid Properties (fp1) node in the Laminar Flow branch defines, from the Velocity field list."
However, in this example, they do not mention about whether we should select Temperautre( ht/fluid1) in the Fluid Properties node under the Laminar Flow branch or not. Does that mean this choice can't affect the result?

And,for my case, I also have a heat transfer interface for heat transfer in solids, should I select "Temperature (ht/solid1)" in the fluid properties of Laminar Flow,or just leave it as "User defined"?

Thanks and Best Regards.
6 Replies Last Post 12 déc. 2014, 11:54 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 11 mai 2011, 12:03 UTC−4
Hi

you have the predefined heat fluidics/solid = nitf (conjugated heat transfer / non-isothermal flow) physics, where everything is set up for you

--
Good luck
Ivar
Hi you have the predefined heat fluidics/solid = nitf (conjugated heat transfer / non-isothermal flow) physics, where everything is set up for you -- Good luck Ivar
Ting Yan
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Posted: 1 decade ago 13 mai 2011, 04:54 UTC−4

Hi

you have the predefined heat fluidics/solid = nitf (conjugated heat transfer / non-isothermal flow) physics, where everything is set up for you

--
Good luck
Ivar


Hi Ivar,

Thank you for your suggestion. Now there is another problem

I tried to take your suggestion and use "nitf " physics to solve my model again. However, when I chose mesh as " user-controlled" and set "coarse" mesh for the fluid dynamics, the simulation result was too strange and totally different from what I excepted and simulated in multiphyscis couplings.

Could you do me a favor to give me some hints for this cfd model? ( I uploaded both cfd model and multiphysics couplings model)

Best Regards.

Ting
[QUOTE] Hi you have the predefined heat fluidics/solid = nitf (conjugated heat transfer / non-isothermal flow) physics, where everything is set up for you -- Good luck Ivar [/QUOTE] Hi Ivar, Thank you for your suggestion. Now there is another problem I tried to take your suggestion and use "nitf " physics to solve my model again. However, when I chose mesh as " user-controlled" and set "coarse" mesh for the fluid dynamics, the simulation result was too strange and totally different from what I excepted and simulated in multiphyscis couplings. Could you do me a favor to give me some hints for this cfd model? ( I uploaded both cfd model and multiphysics couplings model) Best Regards. Ting
Amir Fadel
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Posted: 1 decade ago 13 mai 2011, 09:08 UTC−4
Hi,

If you look at your nesh is definitely not good, it shlud be much more homogeneous whenever possible.

I re-meshed your model and I got a nice solution for the model you called 2_3 velocity no ht, be careful because in this model there is heat transfer and the nice color picture you get is about the T distrbution. Because of size limit I uploaded the file without the solution you just need to compute it again.

Look carefully at the mesh, it is much more regular now than yours. In CFD/HT meshing is probably the most difficult task or the second diffcult one.

I could not get convergence on your other model, you need to go through it carefully.

Cheers
Hi, If you look at your nesh is definitely not good, it shlud be much more homogeneous whenever possible. I re-meshed your model and I got a nice solution for the model you called 2_3 velocity no ht, be careful because in this model there is heat transfer and the nice color picture you get is about the T distrbution. Because of size limit I uploaded the file without the solution you just need to compute it again. Look carefully at the mesh, it is much more regular now than yours. In CFD/HT meshing is probably the most difficult task or the second diffcult one. I could not get convergence on your other model, you need to go through it carefully. Cheers
Ting Yan
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Posted: 1 decade ago 19 mai 2011, 06:28 UTC−4

Hi,

If you look at your nesh is definitely not good, it shlud be much more homogeneous whenever possible.

I re-meshed your model and I got a nice solution for the model you called 2_3 velocity no ht, be careful because in this model there is heat transfer and the nice color picture you get is about the T distrbution. Because of size limit I uploaded the file without the solution you just need to compute it again.

Look carefully at the mesh, it is much more regular now than yours. In CFD/HT meshing is probably the most difficult task or the second diffcult one.

I could not get convergence on your other model, you need to go through it carefully.

Cheers


Hi Amir,

Thank you for your suggestion. I already got the simulation result from your remesh model. It looks nice. However, when I try to do the same remesh (like you did) for my other old models, they gave some unreasonable result, more than 800 degree.
Would you do me a favor to tell me what's wrong with my remesh method?
I also just uploaded the "old mesh model " (2_5 veloticy no ht) and Remesh model (2_5 velocity no ht Remesh) without the solution.

By the way, for my first question, do you have any idea whether I should choose "Temperature(ht/Solid1)" in the "Fluid Properties" under "Laminar Flow" Tree?

Thank you very much

Ting

[QUOTE] Hi, If you look at your nesh is definitely not good, it shlud be much more homogeneous whenever possible. I re-meshed your model and I got a nice solution for the model you called 2_3 velocity no ht, be careful because in this model there is heat transfer and the nice color picture you get is about the T distrbution. Because of size limit I uploaded the file without the solution you just need to compute it again. Look carefully at the mesh, it is much more regular now than yours. In CFD/HT meshing is probably the most difficult task or the second diffcult one. I could not get convergence on your other model, you need to go through it carefully. Cheers [/QUOTE] Hi Amir, Thank you for your suggestion. I already got the simulation result from your remesh model. It looks nice. However, when I try to do the same remesh (like you did) for my other old models, they gave some unreasonable result, more than 800 degree. Would you do me a favor to tell me what's wrong with my remesh method? I also just uploaded the "old mesh model " (2_5 veloticy no ht) and Remesh model (2_5 velocity no ht Remesh) without the solution. By the way, for my first question, do you have any idea whether I should choose "Temperature(ht/Solid1)" in the "Fluid Properties" under "Laminar Flow" Tree? Thank you very much Ting
Amir Fadel
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Posted: 1 decade ago 19 mai 2011, 09:01 UTC−4
Hi,

I have defined a mesh for Domain 1 and a different mesh for Domain 2. You need to tweack the settings of the two meshes, it is unlikely they can be the same because the two domains have different geometries, one domain is made up of small square tubes and one domain is the encasing of the tubes. You can also select a seeding density on the edges of the encasing (or of the tubes), the possibilities are almost infinite, it is just important you have a regularly spaced mesh.

In another example I have refined your mesh also on Domain 1 by modifying the generic Size tab you find in the mesh tree, see the file. Regarding the "Temperature(ht/Solid1)" if in the example they don't say anything you don't have to touch it. If you leave "Temperature(ht/Solid1)" then comsol should import the temperature from the ht interface, whereas if you define it yourself you will decide which value to start with.

Your temperature is extremely high because of the extremely high heat flux you have defined, if you lower it T will drop, make sure it is correct.

Cheers
Hi, I have defined a mesh for Domain 1 and a different mesh for Domain 2. You need to tweack the settings of the two meshes, it is unlikely they can be the same because the two domains have different geometries, one domain is made up of small square tubes and one domain is the encasing of the tubes. You can also select a seeding density on the edges of the encasing (or of the tubes), the possibilities are almost infinite, it is just important you have a regularly spaced mesh. In another example I have refined your mesh also on Domain 1 by modifying the generic Size tab you find in the mesh tree, see the file. Regarding the "Temperature(ht/Solid1)" if in the example they don't say anything you don't have to touch it. If you leave "Temperature(ht/Solid1)" then comsol should import the temperature from the ht interface, whereas if you define it yourself you will decide which value to start with. Your temperature is extremely high because of the extremely high heat flux you have defined, if you lower it T will drop, make sure it is correct. Cheers
Kimia Mortezaei
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Posted: 10 years ago 12 déc. 2014, 11:54 UTC−5
I would like to know if it is possible to see the coupled equations in COMSOL. As you know, we are only able to see the equations for each physic.
I would like to know if it is possible to see the coupled equations in COMSOL. As you know, we are only able to see the equations for each physic.

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