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Problem with Joule-Heating simulation in a high aspect-ratio system

Hello,

I have a problem with a code which I have written to simulate Joule-Heating through a 3D cubic system made of silver. When the aspect ratio between l_x/l_y (l_x and l_y are the length of the system in x and y direction) is less than 100, I get good results from the code independent of the number of grid points generated in the system. However, when the l_x/l_y is larger than 100, the temperature distribution predicted by the model shows deviations from a true symmetric distribution for even 30000 grid points which are not really large. What could be the problem? I have used a resistive networks to solve electrical and heat conduction equations.

I appreciate for any help.

 Rami November 29, 2012 04:28

• Are you using a CFD package, and if so - which?
• With a large aspect ratio, did you also use high aspect ration cells? If so - it can explain the difficultiy you are experiencing.
• You did not mention the Lz / Lx ratio. Please specify.
Rami

Quote:
 Originally Posted by Rami (Post 394813) Hi Farshad, Are you using a CFD package, and if so - which? With a large aspect ratio, did you also use high aspect ration cells? If so - it can explain the difficultiy you are experiencing. You did not mention the Lz / Lx ratio. Please specify. Rami
Hi Rami,

Thanks for your answer. I am using our in-house code which is basically a Finite-Difference code. I think you are right. Because I try to shrink the aspect ratio of the grids in the high-aspect ratio case and now it's giving me the right answer. Lz/Lx = 1.

Thanks again,

Quote:
 Originally Posted by farshadsm (Post 394845) Hi Rami, Thanks for your answer. I am using our in-house code which is basically a Finite-Difference code. I think you are right. Because I try to shrink the aspect ratio of the grids in the high-aspect ratio case and now it's giving me the right answer. Lz/Lx = 1. Thanks again, Farshad
Rami,

Is there any mathematical rule or basis for choosing the correct value for the time step as well as grid boxes for large geometrical aspect ratio?