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March 3, 2010 11:14pm UTC

Extrusion coupling variables

Hello,

I have a model that consists of two geometries: one in 1D and the other in 2D axial symmetry. For each time step, I want the values attained by solving for one of my variables from a line boundary in the 2D axial symmetry to be used to solve for a second variable in the 1D geometry. After this variable is solved for in the 1D geometry, I want these values used to solve for the first variable in the 2D axial symmetry geometry. I want this to occur repeatedly so that my model is continuously sending the last solved for values in one geometry to the other geometry. My line in 2D axial symmetry space is the same length as the line in 1D, so I believe I want to do a linear transformation with "extrusion coupling variables". I have tried to set up two linear transformations, but am not getting my model to work properly. Does anyone have any insight for this problem?

Thanks,
Andrew

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March 4, 2010 4:13pm UTC in response to Jean-Francois Leon

Re: Extrusion coupling variables

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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March 11, 2010 9:22pm UTC in response to Jean-Francois Leon

Re: Extrusion coupling variables

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

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