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Difference between 2D and 3D !

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Old   January 25, 2005, 04:59
Default Difference between 2D and 3D !
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Hi everybody !

I would be very pleased if someone could give me information about a "possible mistake" I made in a modelisation.

I made a 3D case modeling a combustion in a closed volume. Source is a exit nozzle and boundary condition is "pressure inlet" (I know P, T0 and Pstat). I get the convergence and analyse pressure and temperature fieds on the wall in front of the exit source (3,00 m away).

I try to realize an equivalent in 2D with an axisymmetric case. The boundary condition "axis" is along the x-axis. I kept the source data defined for 3d case. I mesh the plane with size-function along x that is to say along the flow.

The trouble is that I do not get the same result in pressure and temperature (20% different) and the time the flow impact the wall target is greater in the 2d case (6 ms) than for the 3d (3.5 ms).

What could be the matter ? Time-step ? Use of a size function ?

I hope this trouble could find a answer...

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Old   January 25, 2005, 13:21
Default Re: Difference between 2D and 3D !
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First of all, try to reproduce the mesh you used in 3D in the Axi case.

However, I had similar problems in many cases. Usually a flow is not fully symmetrical, so using the axi solver might not be appropriate.

Hi, ap
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Old   January 26, 2005, 04:10
Default Re: Difference between 2D and 3D !
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Thanks for your answer.

In fact I am not sure that the size function used in the 2d case is the same than in the 3D.

I will check it now.

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