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Cannot produce identical result between 3D and axissymmetric 2D

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Old   March 5, 2014, 14:01
Unhappy Cannot produce identical result between 3D and axissymmetric 2D
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ZJoy
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Dear Foamers,

I'm testing simpleFoam simulation of a steady incompressible laminar flow on an axissymetric 2D model and the 3D model. The 3D model is a simple straight pipe with narrowed radius in middle section. The 2D model is the wedge shaped pipe with two patches (front and back) of wedge angle < 5 degree. The conditions setup are same between the 2D and 3D models except the flow rate at inlet is adjusted according to the inlet area. However, the result is different, the inlet pressure (0.153) at 3D model is higher than the inlet pressure (0.141) at the 2D model, the difference is about 7%. I cannot figure out what's wrong with the input.Do you have any example or comment for producing identical result on 3D model and corresponding wedge 2D mode? Thanks!

BTW: I'm using OpenFoam version 2.2.2.

Thanks,
Steven
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Old   March 6, 2014, 06:00
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Alexey Matveichev
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Hi,

Can you be more specific?

Can you post case files? If not: Densities of the meshes are identical? What BCs do you use? What's in your fvSchemes and fvSolution?
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Old   March 6, 2014, 10:54
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Thanks. Densities are not identical. I will try to use same meshing pattern to test the result. Boundary condition is volume flow rate at inlet with zero gradient of pressure and at outlet with zero gradient of velocity and fixed value of pressure.
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Old   March 6, 2014, 10:58
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Alexey Matveichev
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What type of BC do you use at the axis?
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