The problem is the following. I consider a 2D rectangularly shaped solid body assuming that the body is cut from a sample of greater length. A heat source acts on the upper surface of the body. I would like to set the boundary conditions on the left, right and bottom surfaces so as the same material of infinite length is in thermal contact with the body. How should I better do it? I would be grateful if you could give me any advice or maybe suggest some literature. Thanks in advance.
There are different types of boundary conditions:1-specified temperature or known temperature, 2-If you have an idea about the heat flux at the boundary surface you can give this flux 3-If you can predict the heat transfer coefficient at the surface you can give it
Hi Olga
I use COMSOL to simulate.
If your 2D solid is a cut of a long parallelepipedic solid there is no gradient perpendicular to your 2D plane.
So for the boundary conditions of the 3 other sides take the conditions of the 3 sides your long solid.
But may be I don't understand your problem.
Best regards
Dear Olga
There is no great difference in a boundary condition to be used. You can use zero heat flux or constant temperature, but the boundaries should be far away from the zone of you interest. Your problem shouldn't feel them. For nonstationary case you can easely calculate the size of the domain from the heat conduction scale x^2=kt .
Dear colleagues,
Thank you very much for your comments and advices. The picture becomes clearer for me.
Basically, there are 4 types of BC: 1st kind or Dirichlet BC (specified temperature), 2nd kind or Neumann BC (specified fkux) and 3rd type or Robin BC (energy balance at the boundary). The fourth type is usually a mixed of the above.
Now, when you cut the specimen, the boundary condition won't be the same as the infinetely long original piece... the specimen is now changed. If you need it to act as the original part, then the aspect ratio should be maintained in terms of length, width, and thickness
I suggest bulilding a large model first and then finding the local temperature distribution of interest. After that you can use the local result as input to the smaller model. This strategy is used in analyzing large heat exchangers.
I have a doubt.
If I have three adjacent planes with differentboundaryconditions, in a 3D domain. Dirichlet (fixed temperature) on one plane, Neumann fixed flux, Neumann fixed heat conduction, then what should I do?
Should I consider all the conditions on the common node? I read somewhere that if Temperature and heat flux is specified on a node then only specified temperature should be considered.
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