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#1 |
New Member
Join Date: Jun 2024
Posts: 5
Rep Power: 2 ![]() |
I am trying to determine the drag coefficient of a circular cylinder diameter 0.03m at Re = 10^5 as a test case before using my mesh etc to investigate the drag and lift of a pentagonal cylinder. For some reason, I am getting a Cd of 0.43 which is much lower than the literature value of 1.2 and I cannot work out why. I am using a RANS k-omega SST solver with a localised mesh which keeps the y+ value between 30-50. Any advice would be much appreciated.
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#2 |
Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,728
Rep Power: 66 ![]() ![]() ![]() |
The most common mistake is people have no idea what a Cd is or how it should be calculated. So...
How do you calculate the Cd? Show all your work. I clicked some reports is akin to I looked it up in the answers section in the back of the book. Can you reproduce the 0.43 if you calculate it by hand? |
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#3 |
New Member
Join Date: Jun 2024
Posts: 5
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Hi LuckyTran,
Thanks for your response. I know how to calculate Cd using Cd = Fd / ((L*D) * U^2 * p * 1/2) and have inputted my reference values correctly so this is not the issue. |
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#4 |
Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,728
Rep Power: 66 ![]() ![]() ![]() |
And this is from a 2D case? 3D case? Again, show your work. Or be content with not getting any help because help is not what you want.
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#5 |
New Member
Join Date: Jun 2024
Posts: 5
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This is for 2D simulation - what do you mean by show working?
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#6 |
New Member
Hou DF
Join Date: Jun 2022
Location: China
Posts: 4
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The 2D problem always had the wrong result for "Force" because in ANSYS Fluent, the default thickness for a 2D case is 1m. Besides, a big yplus value would cause a wrong velocity near the wall, so you might want to check if the velocity near the wall is correct. If the velocity is wrong, the wall shear stress will be wrong too.
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#7 |
New Member
Isha
Join Date: Jun 2024
Posts: 2
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Hey, what value did you put for D and L?
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Tags |
drag coefficients, fluent |
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