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Parallel wires in infinite air

Posted Dec 27, 2011, 6:07 a.m. EST Low-Frequency Electromagnetics, Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD) Version 4.2a 1 Reply

Akmal
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hi All,

i have difficulty to exactly define the boundary condition of my model.

it's about parallel wires (distance betwen them 1[mm] to 30[mm]). First in 2D. If i dont define the air domain, it's impossible to analys interaction of both wires, right? (maybe with boundary pair will work somehow, but i never try this).

Boundary between cable isolation and air is OK, it's not necessary to define anything.

outer boundary of air is a problem.

1. Air is a fluid but air is also an infinite elements. this domain condition (heat transfer in fluids and infinite elements) override each other (sorry my english is overrided by german).

2. then i tried using infinite elements as domain condition and convective cooling as outer boundary condition. The result seems to be correct, but im not sure how to analiticaly validate it.

3. heat transfer in fluids and convective cooling are bad combination.

4. heat transfer in fluids in conbination with open boundary and outflow are wrong. because the temperatur in the midle of wires is the same (at 1mm-30mm wire distance)

5. heat transfer in fluids in conbination with temperatur and outflow are working and looks like the best combination. but im not sure.

please suggest me something. the model is attached.
happy holiday!

akmal
1 Reply Last Post Dec 28, 2011, 4:30 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Dec 28, 2011, 4:30 a.m. EST
Hi

you ae mixing many physics there, but I'm not sure you have sorted out all interactions correctly. i.e. you do not link the temperature and the pressure from the other physics to the fluid flow.

Anyhow, I find you fluid/air domain very small, what are you exactly looking after ? and are you sure you have taken all elements into account ?

Often its worth to decouple the problems, when possible. then couple them but one must be sure all physics get the different values from each other anfd in the right order (using the segregated solver helps).

Also be aware when you load in several physics, sometimes you get twice the dependent variales i.e. T and T2, that is normally one too much ;)

--
Good luck
Ivar
Hi you ae mixing many physics there, but I'm not sure you have sorted out all interactions correctly. i.e. you do not link the temperature and the pressure from the other physics to the fluid flow. Anyhow, I find you fluid/air domain very small, what are you exactly looking after ? and are you sure you have taken all elements into account ? Often its worth to decouple the problems, when possible. then couple them but one must be sure all physics get the different values from each other anfd in the right order (using the segregated solver helps). Also be aware when you load in several physics, sometimes you get twice the dependent variales i.e. T and T2, that is normally one too much ;) -- Good luck Ivar

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