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Free Convection with Open Boundary?

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Old   May 29, 2017, 08:56
Talking Free Convection with Open Boundary?
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Tina Maake
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Hello,

I am modelling a geothermal pipe. For computational reasons I can not Modell the whole 4000 m borehole.
So I restricted the are for 400 m. I want to take a closer look at the free convection, but I am confused what BC for the upper und the downer part may be the correct one.

Open Boundary?
Inlet/outlet?
Or Close the pipe?

At former modelling approaches the convection cells exceeded 400m.
(This is for my master Thesis and I am using comsol multiphysics)

Best regards,

Tina Maake
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Old   May 29, 2017, 23:41
Default open's stress free
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Svetlana Tkachenko
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Hello, I am not familiar with COMSOL, but my novice view is as follows.

- Do not close the pipe, it is like putting a wall.
- Do not use outlet, it requires pressure or velocity (unless zero average static pressure suits you well).
- I would suggest open boundary, it is a stress free boundary condition.
- It is discussed here and there for example.
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boundary condition, comsol, free convection, geothermal, heat transfer

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