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Seperating geometry

Posted Dec 6, 2012, 10:59 a.m. EST 26 Replies

Purvi Trivedi
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I have a very simple model a cube inside a cube, but I cannot apply different materials on them. I want to seperate two cubes so that I can apply two different materials to them.

26 Replies Last Post Dec 8, 2012, 11:03 a.m. EST
Mayur
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Posted: 1 decade ago Dec 6, 2012, 11:32 a.m. EST
Hi,
Attached find the comsol file with the solution you are looking for.
cheers
Mayur
Hi, Attached find the comsol file with the solution you are looking for. cheers Mayur

Attachments:

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Dec 6, 2012, 11:34 a.m. EST
Hi

if you have defined, within COMSOL two blocks (geometrical objects), one inside the other, and you use Geometry Union mode, then you will have 2 "domains" (FEM entities) onto which you might apply a specific material property to each. The COMSOL convention is that when you define several materials, the second node will override any material that is previously defined above, that is if material 1 selects both domains, and material2 (further down) defines material for domain 2, then domain 2 will appear as "overriden" in the material definition 1.

Try it out, if you cannot get 2 domains, then your geometry is not defined correctly

--
Good luck
Ivar
Hi if you have defined, within COMSOL two blocks (geometrical objects), one inside the other, and you use Geometry Union mode, then you will have 2 "domains" (FEM entities) onto which you might apply a specific material property to each. The COMSOL convention is that when you define several materials, the second node will override any material that is previously defined above, that is if material 1 selects both domains, and material2 (further down) defines material for domain 2, then domain 2 will appear as "overriden" in the material definition 1. Try it out, if you cannot get 2 domains, then your geometry is not defined correctly -- Good luck Ivar
Purvi Trivedi
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Posted: 1 decade ago Dec 6, 2012, 5:56 p.m. EST
Hi Mayur,
Thanks for your help but I am not able to open the geometry, because It giving error " Model has been desigen in later version of comsol multiphysics"
Any idea about how you designed it?
Purvi
Hi Mayur, Thanks for your help but I am not able to open the geometry, because It giving error " Model has been desigen in later version of comsol multiphysics" Any idea about how you designed it? Purvi
Purvi Trivedi
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Posted: 1 decade ago Dec 6, 2012, 6:17 p.m. EST
Thanks Ivar,
Can I try using "difference" boolean operator and selecting option " keep input objects"?
I am using this cube model for designing conjugate microchannel heat sink model in conduction heat tranfer
I have selected model as " conjugate heat transfer(nitf)"
one of my inlet B.C. is " Mass flow inlet", and second B.C. is "Wall " where I have to define Wall thichness as "450X10^-6" how can i define it?
Thanks Ivar, Can I try using "difference" boolean operator and selecting option " keep input objects"? I am using this cube model for designing conjugate microchannel heat sink model in conduction heat tranfer I have selected model as " conjugate heat transfer(nitf)" one of my inlet B.C. is " Mass flow inlet", and second B.C. is "Wall " where I have to define Wall thichness as "450X10^-6" how can i define it?
Purvi Trivedi
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Posted: 1 decade ago Dec 6, 2012, 6:23 p.m. EST
Also when I am using diffrence operator my inner cube for faces becomes " not applicable" I mean i can not define B.C. on that surfaces.
Any idea?
Also when I am using diffrence operator my inner cube for faces becomes " not applicable" I mean i can not define B.C. on that surfaces. Any idea?
Mayur
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Posted: 1 decade ago Dec 6, 2012, 6:42 p.m. EST
Hi,
attached find the image files of the model. First create two blocks of different size (_1), then go to transparent option (_2), go to material and select the materials that you want and define them under domains selecting any domain (block) you want (_3).
cheers
Mayur
Hi, attached find the image files of the model. First create two blocks of different size (_1), then go to transparent option (_2), go to material and select the materials that you want and define them under domains selecting any domain (block) you want (_3). cheers Mayur
Purvi Trivedi
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Posted: 1 decade ago Dec 6, 2012, 6:52 p.m. EST
Thanks Mayur,
it worked, but doing this I have four faces of inside cube of type " not applicable". Can I apply any boundary condition on that face?
Thanks Mayur, it worked, but doing this I have four faces of inside cube of type " not applicable". Can I apply any boundary condition on that face?
Mayur
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Posted: 1 decade ago Dec 6, 2012, 6:57 p.m. EST
Hi,
I think so, I just tried in Comsol. Which version of Comsol are you using? I tried in 4.2 as well as 4.3a.
Hi, I think so, I just tried in Comsol. Which version of Comsol are you using? I tried in 4.2 as well as 4.3a.
Purvi Trivedi
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Posted: 1 decade ago Dec 6, 2012, 7:07 p.m. EST
It's 4.3.
It's 4.3.
Mayur
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Posted: 1 decade ago Dec 6, 2012, 7:09 p.m. EST
hi,
if possible send me your model file. I think there must be some way..
Mayur
hi, if possible send me your model file. I think there must be some way.. Mayur
Purvi Trivedi
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Posted: 1 decade ago Dec 6, 2012, 7:11 p.m. EST
Attached my file.
Attached my file.

Attachments:

Mayur
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Posted: 1 decade ago Dec 6, 2012, 7:16 p.m. EST
Also could you please define me what exactly you want to do (objectives)? so that I will get an idea about boundary conditions.
Also could you please define me what exactly you want to do (objectives)? so that I will get an idea about boundary conditions.
Purvi Trivedi
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Posted: 1 decade ago Dec 6, 2012, 7:25 p.m. EST
I am designing a model for " Micro-channel heat sink with one heat sink inside "
I have used model as conjugate heat transfer(nitf)
I am using water as a cooling liquid in outer cube and inner cube material as silicon
My B.C are:
Channel Inlet: Mass flow inlet (how we can apply this B.C. in comsol?)
Channel outlet: Outflow
Heat flux: Bottom wall of heat sink ( i.e. inner cube base)
all other B.C. are wall.
Also I wanted to add wall thickness to wall B.C. Is it possible in comsol?
Thanks for all your help.
Purvi
I am designing a model for " Micro-channel heat sink with one heat sink inside " I have used model as conjugate heat transfer(nitf) I am using water as a cooling liquid in outer cube and inner cube material as silicon My B.C are: Channel Inlet: Mass flow inlet (how we can apply this B.C. in comsol?) Channel outlet: Outflow Heat flux: Bottom wall of heat sink ( i.e. inner cube base) all other B.C. are wall. Also I wanted to add wall thickness to wall B.C. Is it possible in comsol? Thanks for all your help. Purvi
Mayur
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Posted: 1 decade ago Dec 6, 2012, 7:40 p.m. EST
Hi,
First of all, the geometry doesn't look like micro-channel, you created everything in meter unit, check all dimensions. You can define inlet mass flow rate (kg/s) in-terms of inlet velocity. For 3D model B.C is going to be the surface, you can not define volumetric boundary condition. You can define volumetric source term (heat, force or mass). Also very important thing if you don't have enough computational power then it is going to very difficult to solve 3D model, so I recommend to develop 2d model first then go for 3D model.
cheers
Mayur
Hi, First of all, the geometry doesn't look like micro-channel, you created everything in meter unit, check all dimensions. You can define inlet mass flow rate (kg/s) in-terms of inlet velocity. For 3D model B.C is going to be the surface, you can not define volumetric boundary condition. You can define volumetric source term (heat, force or mass). Also very important thing if you don't have enough computational power then it is going to very difficult to solve 3D model, so I recommend to develop 2d model first then go for 3D model. cheers Mayur
Mayur
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Posted: 1 decade ago Dec 6, 2012, 8:27 p.m. EST
Hi,
I have modified your 3d model, and I also created 2d model with constant parameters and solved it. I think you will get some rough idea now how to deal with 3d model. Check out the boundary conditions in 2d model. In 2d model I have considered constant properties of water and silicon which you can modified to temperature dependent easily.
cheers
Mayur
Hi, I have modified your 3d model, and I also created 2d model with constant parameters and solved it. I think you will get some rough idea now how to deal with 3d model. Check out the boundary conditions in 2d model. In 2d model I have considered constant properties of water and silicon which you can modified to temperature dependent easily. cheers Mayur
Mayur
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Posted: 1 decade ago Dec 6, 2012, 8:49 p.m. EST
I have tried to define everything. The problem was, you are trying to implement heat flux boundary condition at the base of the silicon which is not possible because in coupled model (heat and fluid flow), the boundaries of the inside cube (silicon) are by default defined in Comsol with continuity boundary condition which connect the outer cube (water region). Now, if silicon is acting as a heat sink which I assume it is cooling some other heating element or it is absorbing heat of another heating element (or heat source); you need to create a surface contact of silicon base with that heating element (or heat source) which you are trying to cool (if I understood correctly). In the attached model I tried to do this by modifying the geometry of the silicon so that it should be in contact with some external heat source (not defined in geometry) and by implementing boundary heat source on boundary 4 (base of the silicon).
I have tried to define everything. The problem was, you are trying to implement heat flux boundary condition at the base of the silicon which is not possible because in coupled model (heat and fluid flow), the boundaries of the inside cube (silicon) are by default defined in Comsol with continuity boundary condition which connect the outer cube (water region). Now, if silicon is acting as a heat sink which I assume it is cooling some other heating element or it is absorbing heat of another heating element (or heat source); you need to create a surface contact of silicon base with that heating element (or heat source) which you are trying to cool (if I understood correctly). In the attached model I tried to do this by modifying the geometry of the silicon so that it should be in contact with some external heat source (not defined in geometry) and by implementing boundary heat source on boundary 4 (base of the silicon).
Purvi Trivedi
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Posted: 1 decade ago Dec 7, 2012, 2:22 p.m. EST
Thanks Mayur.
I will try this out again for my practice.
Thanks for all your support.
Purvi
Thanks Mayur. I will try this out again for my practice. Thanks for all your support. Purvi
Purvi Trivedi
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Posted: 1 decade ago Dec 7, 2012, 7:07 p.m. EST
Hi Mayur,
I tried in the way you defined the geometry for 3D. It is really helpful for my understanding.
But Still the geometry what i was planning to desing has dimebsion
100X900X10000
Where each heat sink has dimension 57X180X10000
and there is equal length from each node in X-direction.
I am attaching the geometry of what I am trying to design with this. Where actually sink is somwhere inside the channel and not exactly at the base how you defined in the model.
So I think I have to use boolean operator.
But When I am using boolean operator some of the surface creates like " over ridden"
Thanks again,
Purvi
Hi Mayur, I tried in the way you defined the geometry for 3D. It is really helpful for my understanding. But Still the geometry what i was planning to desing has dimebsion 100X900X10000 Where each heat sink has dimension 57X180X10000 and there is equal length from each node in X-direction. I am attaching the geometry of what I am trying to design with this. Where actually sink is somwhere inside the channel and not exactly at the base how you defined in the model. So I think I have to use boolean operator. But When I am using boolean operator some of the surface creates like " over ridden" Thanks again, Purvi

Attachments:

Mayur
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Posted: 1 decade ago Dec 7, 2012, 8:52 p.m. EST
are you trying to replicate the result published in International Journal of Heat and Mass Transfer 47 (2004) 4215–423?
are you trying to replicate the result published in International Journal of Heat and Mass Transfer 47 (2004) 4215–423?
Purvi Trivedi
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Posted: 1 decade ago Dec 7, 2012, 8:59 p.m. EST
Yes, I am trying to use this geometry for my practice.
Yes, I am trying to use this geometry for my practice.
Purvi Trivedi
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Posted: 1 decade ago Dec 7, 2012, 9:00 p.m. EST
I mean same geometry of International Journal of Heat and Mass Transfer 47 (2004) 4215–423?
I mean same geometry of International Journal of Heat and Mass Transfer 47 (2004) 4215–423?
Mayur
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Posted: 1 decade ago Dec 7, 2012, 9:12 p.m. EST
okay, after looking at this paper, it seems water is flowing through the cyan color channel (Fig 1 and 2 in paper), actually you tried exactly opposite to what is given in the paper.
okay, after looking at this paper, it seems water is flowing through the cyan color channel (Fig 1 and 2 in paper), actually you tried exactly opposite to what is given in the paper.
Purvi Trivedi
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Posted: 1 decade ago Dec 7, 2012, 9:36 p.m. EST
Yes I think You are write in this channels are inside containing water.
My basic problem is defining geometry
Yes I think You are write in this channels are inside containing water. My basic problem is defining geometry
Mayur
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Posted: 1 decade ago Dec 7, 2012, 10:00 p.m. EST
attached find the modified model, i think everything is done. I am actually having cold and sitting at home free, I have almost finished your project..:)
cheers
Mayur
attached find the modified model, i think everything is done. I am actually having cold and sitting at home free, I have almost finished your project..:) cheers Mayur
Purvi Trivedi
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Posted: 1 decade ago Dec 7, 2012, 11:30 p.m. EST
Thank you soooo much Mayur.
I really appreciate your support.
I will try it out tomorrow and v'l let you know.
Purvi
Thank you soooo much Mayur. I really appreciate your support. I will try it out tomorrow and v'l let you know. Purvi
Purvi Trivedi
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Posted: 1 decade ago Dec 8, 2012, 11:03 a.m. EST
Hi, Can you attach modified model for geometry?
It is not attached with your previous message.
Thanks a lot.
It will be a great help for me.
Purvi
Hi, Can you attach modified model for geometry? It is not attached with your previous message. Thanks a lot. It will be a great help for me. Purvi

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