Concordia University Montreal
Question
Asked 5th Jul, 2016
Can a 2D CFD flow simulation give accurate result as a 3D simulation, How could we determine which is suitable?
While simulating fluids using CFD tools on 2D / planar mesh and 3D / volume mesh the flow will differ according to the cross-section obviously. In case of a flow mixing simulation, if the cross-section of both channel is rectangle a planar mesh solution gives similar result to a 3D mesh, whereas if the channel is of any other cross-section the flow physics shall vary.
Attachments show analysis result of 2D and 3D mesh of a flow mixing with similar boundary conditions and meshing setup.
What is the criteria for choosing in between 2D and 3D mesh?
Do the analyses which used the 2D mesh strictly adhere to itself rather than a general setup?
Most recent answer
I am wondering what will be the differences if we are comparing a 2D planner and 2D axisymmetric simulations. What parameters should be changed such that the two cases are comparable?
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Popular answers (1)
von Karman Institute for Fluid Dynamics
It depends on many parameters, besides the geometry of course.
The first thing I would recall is turbulence. Mixing and more generally diffusion phenomena are never purely 2D. If you are in turbulent conditions and you are using RANS models, 3D diffusion might be accounted for by the transport equation of your turbulence quantities. If you are under laminar conditions, then everything depends on you geometry.
In your case, is the aspect ratio of your geometry sufficiently large (say above 50) ? If that is the case then there should not be much difference. You can consider a 2D simulation as a 3D simulation in which the third dimension is much larger than any other dimension.
Computational cost (size of your mesh) and required accuracy are then the two things that should guide you in the decision between the two approaches
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All Answers (8)
von Karman Institute for Fluid Dynamics
It depends on many parameters, besides the geometry of course.
The first thing I would recall is turbulence. Mixing and more generally diffusion phenomena are never purely 2D. If you are in turbulent conditions and you are using RANS models, 3D diffusion might be accounted for by the transport equation of your turbulence quantities. If you are under laminar conditions, then everything depends on you geometry.
In your case, is the aspect ratio of your geometry sufficiently large (say above 50) ? If that is the case then there should not be much difference. You can consider a 2D simulation as a 3D simulation in which the third dimension is much larger than any other dimension.
Computational cost (size of your mesh) and required accuracy are then the two things that should guide you in the decision between the two approaches
3 Recommendations
Shiraz University of Technology
Hi
2D CFD flow simulation can not give accurate result as a 3D simulation,exactly.
but their result can be Similar with together, nearly.
nota bene that you can use 2D simulation instead of 3ِD when your Geometry is simultaneous, If your Geometry is not simultaneous, you can not take similar results 2D and 3D.
For example, Geometry is Ogee spillway with thickness 1 m, so you can Regardless of thickness and simulation 2D. that results of 2D and 3D are similar. but if your Geometry is channel, you can not use 2D simulation instead of 3D. because flow is different
Conditions in depth.
any time, 2D CFD flow simulation can not give accurate result as a 3D simulation,exactly.
Good Luck!
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Dear Manu
The 2D model suggest that the inlet represent a slot geometry and closely match a 3D model with large aspect ratio of rectangular inlet channel. If the 3d model is of circular shape, and the 2d model assumed the inlet size is equal to the diameter of 3d inlet, the mass flux will be different if the secondary fluid speed for both cases take the same value
Aziz
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Amrita Institute of Medical Sciences and Research Centre
Thanks alot
Mendez : Analytical geometry is not too much deep (not bigger than the breadth of the geometry), I think the problem is the mass flux calculation is wrong as Abdul Aziz suggested. I assumed the mass flux of a rectangular slot for 2D and discrete holes in 3D also the hole geometries are circular, mass flux correction may correct the problem.
Souroush: Thanks for the suggestion, I will re calculate and check.
Aziz: Thank you
National University of the Center of the Buenos Aires Province
Could you please list the boundary conditions of the problem?
Indian Institute of Technology Bombay
It depends upon the side cross-section if same is extended in the 3rd direction and of course Aspect ratio.
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National University of the Center of the Buenos Aires Province
We recently discussed this in for a flow in X junture. It not only depends on the aspect ratio, the geometry itself is important.
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