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Hello everybody, I am trying to solve a 2D Heat Tranfer conduction problem and I am having some trouble trying to draw the geometry in the right way. I would be glad if you could help me or give me some ideas to solve this problem:

I am trying to simulate the heat transfer between an underground wire (which generates heat because of the Joule effect) and the soil that surrounds the wire. To do this, I have drawn some circles which represent the wire with all its layers (which dimensions are some milimeters) and a semicircle that represents the soil and which has a lot of meters of diameter.

When trying to do this, either COMSOL gives an error ("Edges are too close in 2D domain") or it does not give any errors but materials are wrongly assigned and some domains are fused so that I cannot correctly assign the materials even if I try.

II think that the problem is that I am mixing big and small dimensions. Is there any way to solve this problem?

Solutions that I have already tried:

- To modify the relative repair tolerance, but the problem persisted.

- To use an infinite element domain to use smaller dimensions for the soil; but it gives another problem. The solution changes whenever I modify the size of the soil and consequently the size of the infinite element domain.

Thanks in advance for your help. Any advice would be really appreciated.

Regards,
Diego Fernández