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Posted:
1 decade ago
Mar 3, 2010, 7:10 PM EST

can you post your model?

could be helpful...

jf

can you post your model?
could be helpful...
jf

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Posted:
1 decade ago
Mar 4, 2010, 11:13 AM EST

My model is attached. Geometry 1 is a 2D axial symmetry rectangle where I am modeling heat transport by conduction. Geometry 2 is a 1D line where I am modeling heat flow from water flowing down a pipe. I am using the Comsol Multiphysics, Heat Transfer, Conduction, transient analysis for the application mode of the 2D axial symmetry geometry and the PDE Mode, Coefficient Form, Time-dependent analysis for the application mode of the 1D geometry. I am using the PDE Coefficient Mode so that I could insert my own PDE equation to simulate heat flow down a pipe with a diffusion coefficient, an absorption coefficient, a source term, a damping/mass coefficient, and a convection coefficient.

I want my model to solve for T (block temperature) in the 2D geometry (rectangle) and use the T values along boundary 1 (or r=0) to insert into the equation to solve for w (water temperature) along the line in geometry 2 (T is in the source term for the PDE coefficients). Then I want the w values from geometry 2 to be used to solve for the heat flux boundary condition along boundary 1 (or r=0) in the 2D rectangle. I want both of these geometries to continually provide each other with updated T or w values. I believe I should be able to do this by setting up 2 extrusion coupling variables, but I have not been able to make it work yet.

Everything is set to 283.15 K (10 C) initially, and the input of my 1D pipe has a sine wave where temperatures should fluctuate between 273.15 K (0 C) and 293.15 K (20 C). I have assigned a constant water velocity (u=1 m/s) down the pipe so I shouldn't need to simulate fluid flow with this model.

Does anyone have any insight as to why I haven't been able to couple my variables correctly?

Thanks,

Andrew

My model is attached. Geometry 1 is a 2D axial symmetry rectangle where I am modeling heat transport by conduction. Geometry 2 is a 1D line where I am modeling heat flow from water flowing down a pipe. I am using the Comsol Multiphysics, Heat Transfer, Conduction, transient analysis for the application mode of the 2D axial symmetry geometry and the PDE Mode, Coefficient Form, Time-dependent analysis for the application mode of the 1D geometry. I am using the PDE Coefficient Mode so that I could insert my own PDE equation to simulate heat flow down a pipe with a diffusion coefficient, an absorption coefficient, a source term, a damping/mass coefficient, and a convection coefficient.
I want my model to solve for T (block temperature) in the 2D geometry (rectangle) and use the T values along boundary 1 (or r=0) to insert into the equation to solve for w (water temperature) along the line in geometry 2 (T is in the source term for the PDE coefficients). Then I want the w values from geometry 2 to be used to solve for the heat flux boundary condition along boundary 1 (or r=0) in the 2D rectangle. I want both of these geometries to continually provide each other with updated T or w values. I believe I should be able to do this by setting up 2 extrusion coupling variables, but I have not been able to make it work yet.
Everything is set to 283.15 K (10 C) initially, and the input of my 1D pipe has a sine wave where temperatures should fluctuate between 273.15 K (0 C) and 293.15 K (20 C). I have assigned a constant water velocity (u=1 m/s) down the pipe so I shouldn't need to simulate fluid flow with this model.
Does anyone have any insight as to why I haven't been able to couple my variables correctly?
Thanks,
Andrew

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Posted:
1 decade ago
Mar 11, 2010, 2:58 PM EST

well I looked at your model and the first thing that catch my eye is that your pipe is at r=o.

So the heat flux wil be coupled to a null area. I beloeve that your block should start at coordinate rp rp being your pipe radius.

Indeed axi symmetric has 2*pi*r term invlved and I dont know how it will handle a flux at r=0.

did you think of that..?

second

In your 1d geometry why did you make so many subdomain?

it is possible that it screw your extrudsio n process

SO in short I will recommend to use only One 1d subdomain

I will start my axisymmetric block at the radius of my pipe and not zero...

Once this is done if ti does not fix it we should look for somehting else...

good luck

jf

well I looked at your model and the first thing that catch my eye is that your pipe is at r=o.
So the heat flux wil be coupled to a null area. I beloeve that your block should start at coordinate rp rp being your pipe radius.
Indeed axi symmetric has 2*pi*r term invlved and I dont know how it will handle a flux at r=0.
did you think of that..?
second
In your 1d geometry why did you make so many subdomain?
it is possible that it screw your extrudsio n process
SO in short I will recommend to use only One 1d subdomain
I will start my axisymmetric block at the radius of my pipe and not zero...
Once this is done if ti does not fix it we should look for somehting else...
good luck
jf

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Posted:
1 decade ago
Mar 11, 2010, 4:22 PM EST

JF,

Thank you. The pipe at r=0 was indeed the problem. I moved the edge of the block to the pipe radius, and my model now appears to be running correctly. I overlooked the problem that this would create.

When I created the line in 1D, I didn't specify the number of subdomains. The default was 1000 subdomains, the length of my pipe. However, the edge of the block at r=0 was most likely the biggest problem.

Thanks again,

Andrew

JF,
Thank you. The pipe at r=0 was indeed the problem. I moved the edge of the block to the pipe radius, and my model now appears to be running correctly. I overlooked the problem that this would create.
When I created the line in 1D, I didn't specify the number of subdomains. The default was 1000 subdomains, the length of my pipe. However, the edge of the block at r=0 was most likely the biggest problem.
Thanks again,
Andrew