How to make a CFD analysis ? (ppt) (I'm using fluent))

andrewmichael · May 14, 2015, 15:16

Hello guys,

I'm new to the CFD concept. I had studied a elbow (the first tutorial from ANSYS 14.5 pdf) in fluent with different number of the elements for the mesh (50k, 100k, 200k, 400k, 800k of elements).
After I had started to compare the contours of velocity and temperature, velocity and temperature profiles between the meshes. I had the results but I don't know how to put them together, as to choose the mesh with the best properties.

edoan · May 14, 2015, 15:46

Sounds like what you are doing is a mesh independence check. What you want to do is take your quantity of interest and quantitatively compare it between two mesh adjacent sizes. When the difference is below an acceptable threshold (maybe 5 or 2 percent change depending on what you want) you have found the "best" mesh a compromise between accuracy and resources. Note that even though a solution is grid independent it does not mean it is physically correct. You can achieve grid independence for bad physical models bad boundary conditions etc.

May 14, 2015, 15:16	How to make a CFD analysis ? (ppt) (I'm using fluent))	#1
andrewmichael New Member Bota Amdrei Join Date: May 2015 Posts: 13 Rep Power: 10	Hello guys, I'm new to the CFD concept. I had studied a elbow (the first tutorial from ANSYS 14.5 pdf) in fluent with different number of the elements for the mesh (50k, 100k, 200k, 400k, 800k of elements). After I had started to compare the contours of velocity and temperature, velocity and temperature profiles between the meshes. I had the results but I don't know how to put them together, as to choose the mesh with the best properties.

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May 14, 2015, 15:46		#2
edoan Member Ethan Doan Join Date: Oct 2012 Location: Canada Posts: 90 Rep Power: 13	Sounds like what you are doing is a mesh independence check. What you want to do is take your quantity of interest and quantitatively compare it between two mesh adjacent sizes. When the difference is below an acceptable threshold (maybe 5 or 2 percent change depending on what you want) you have found the "best" mesh a compromise between accuracy and resources. Note that even though a solution is grid independent it does not mean it is physically correct. You can achieve grid independence for bad physical models bad boundary conditions etc.