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How can I get Drag Coeffiecent

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Old   April 18, 2006, 07:04
Default How can I get Drag Coeffiecent
  #1
sanxian
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I am simulating the vortex shedding of 2-d cylinder. But I am wondering if I can get the drag coeffiecent by fluent automatically. Use Solve/Monitor/Force to get the Cd history line is right or not? Thanks for help!
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Old   April 18, 2006, 07:50
Default Re: How can I get Drag Coeffiecent
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Cyril
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That's right !

Make shure you're using the right "references values" like speed, cylender area, ...

Hope that helps !
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Old   April 18, 2006, 07:54
Default Re: How can I get Drag Coeffiecent
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sanxian
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As you said, should I change the reference values as what I have calculated in my case? Thank you for your help? Do you have an MSN? I think maybe we can talk about it furthermore.
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Old   April 18, 2006, 08:00
Default Re: How can I get Drag Coeffiecent
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Cyril
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'dont have msn

About your ref. values, fluent automatically alculate for an area of 1 (I already had the same problem) If you don't change it, you will have very low coefficients. (make shure your mesh is big enough at the rear of your cylinder)

If you've already calculate your drag, you will see very soon if you're right !

good luck
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Old   April 18, 2006, 08:26
Default Re: How can I get Drag Coeffiecent
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sanxian
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In my case, the flow velocity is 1m/s,and the component of the water is the default value in Fluent. The diameter of the cylider is 2m. My case is 2D and I change the density of the reference value, so the Cd value is about 1.25, is more similar as the value shown in many references. I am wondering if I should do other changes and if what I have done is right. Thanks a lot, Cyril. My email address: qdsanxian@hotmail.com Hope to be your friend.
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Old   April 18, 2006, 08:30
Default Re: How can I get Drag Coeffiecent
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Cyril
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Cylinder+2D = 2D axi... (if you didn't, my advice would be to use the 2Daxi model, quicker (half cells), and same accuracy)
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Old   April 18, 2006, 09:03
Default Re: How can I get Drag Coeffiecent
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sanxian
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Ok, thank you. Should I change other reference values in the sheet of "reference value"?
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Old   April 18, 2006, 09:13
Default Re: How can I get Drag Coeffiecent
  #8
Cyril
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Ref values usually upload thmselves when selecting "compute fom".

In 2D area stays as a default value=1.

Others shoul change automatically. Check so that you've got your values and not default ones (speed, ...)

Be shure you've selected your entire model (wall for the cylinder) in the monitor/forces/drag menu.

That should works !

by the way, what's U're name ?
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Old   April 18, 2006, 10:27
Default Re: How can I get Drag Coeffiecent
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sanxian
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Thank you for your help. My name is Liuzhen? Can you pronounce it? I am a Chinese graduated student for doctor courses to study in Korea Maritime University as the exchange student. My former University is Ocean University of China. What about you?

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Old   April 18, 2006, 10:32
Default Re: How can I get Drag Coeffiecent
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Cyril
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My name's Cyril.

Sutdent in an aeronautic engeneering school (The IPSA), in Paris, France.

I've just finished my studies (6 month left, in internship).

glad to meet you.
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Old   April 22, 2006, 05:44
Default Re: How can I get Drag Coeffiecent
  #11
Mr.Ta
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Dear all. I am learning the phenomenon of the flow over a cylinder (especially Vortex shedding) using FLUENT, but i don't know how to model in FLUENT, because i did, but the result is not exact compare to experience. i can't see the vortex shedding even with the Re >=200. help me right now, i need your help. I am a final year student, major of aeronautical engineering, Hanoi university of technology, hanoi, vietnam. Besh wishes.
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Old   April 22, 2006, 05:48
Default Re: How can I get Drag Coeffiecent
  #12
Mr.Ta
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My email is: mrquangngoc@gmail.com Yahoo nick: ngocbkat46 Thanks any your help !!!
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