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axisymmetric comparing to 3D

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Old   February 1, 2006, 04:49
Default axisymmetric comparing to 3D
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BB
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Hello!

Did anyone compare 2d axisymmetric simulation results with the ones done in 3d? How do they match?

In my experience these two methods give me somewhat different results, but I still havent done any analisys about that.

tnx, BB.
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Old   February 1, 2006, 06:06
Default Re: axisymmetric comparing to 3D
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vijay
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I too got a huge difference between those two. But I could not find the reason for that
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Old   February 1, 2006, 13:15
Default Re: axisymmetric comparing to 3D
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Evan Rosenbaum
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How well they compare obviously depends on your particular problem. We have done a few comparisons of axi vs. 3D, and have found that the 3D is not too much different. We happen to have a flow that is primarily axial, though, so you cannot expect the same from all problems.
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Old   February 4, 2006, 04:26
Default Re: axisymmetric comparing to 3D
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kharicha
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Your question is too general....

Let's take a flow within a cylinder, driven by what ever...

When you solve with 2D axisym. you will find only the solution which doesn't change in the theta direction.

When you switch to 3D, waves can occur and travel in the theta direction. So Your solution can become periodic in the theta direction, i.e the solution repeats every Dtheta (=<2pi).

But in some cases, when the flow reach the chaotic regime, your solution becomes totally unsymmetric....But this hard to model.

When the turbulent regime is reached then a symmetry of the mean flow could be restablished....

So in general, for small Re your 3D solution should be axisymmetric....otherwise you have a problem...

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