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April 12, 2013, 00:40 |
Difference between 2D and 2D axisymetric
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#1 |
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Hello,
Im solving a flow through circular pipe. I am specifying pressure drop. When I use a axisymetric case, I get the velocity as per the Hagen Poiseuille Equation. But when I try to solve it using a 2D case it gives me velocity exactly twice of the axisymmetric case. Or simply put the avg. velocity which I am getting after running a 2D case is twice as what I should get from the Hagen Poiseuille Equation. Where can I possibly go wrong while simulating these two cases? Thanks. Varad |
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April 12, 2013, 00:45 |
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#2 |
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Or simply put the avg. velocity which I am getting after running a 2D case is twice as what I should get from the Hagen Poiseuille Equation.
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April 12, 2013, 02:19 |
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#3 |
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Rick
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2d axisymmetric simulates a cilindrical pipe, 2d simulation a square/rectangular duct; what are your boundary conditions?under reference values what is the value for "depth"?
Daniele |
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April 12, 2013, 09:30 |
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#4 |
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Reference value for depth is 1..
pressure inlet and pressure outlet with no slip conditions on the walls.. |
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April 14, 2013, 02:04 |
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#5 |
Super Moderator
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I would like to add further. For shapes other than cylinder, rectangle and square you have to model it as quarter or half symmetrical at least (3D).
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April 14, 2013, 11:06 |
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#6 |
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Thank you guys for ur replies..
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April 14, 2013, 11:19 |
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#7 | |
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Rick
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Quote:
Daniele |
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April 14, 2013, 20:14 |
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#8 |
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Stuart Buckingham
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No, this is incorrect. 2D models are infinitely long in the spanwise direction (Z axis, which you are not modelling). Any geometry that has a finite span, or does not have a perfect cylindrical cross section at all stations along its length must be modeled in 3D.
Stu |
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April 15, 2013, 13:09 |
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#9 | |
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Rick
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Quote:
However I meant that if you are assigning for example an inlet velocity of 1 m/s and you have set a depth of 1 m with the inlet edge 0,2 m long your resulting flowrate will be 0,2x1x1 m3/s. For sure you are not modeling z interactions. Daniele |
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