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 fpz July 5, 2005 22:32

vortex formation length

Hi, everyone, I am puzzled with the defination of vortex formation length behind an circular cylinder. Some paper use the distance between the center of the cylinder and the u=0 position on the symmetry line of the wake. Some use the postion of the maximum fluctuating value of u on the symmetry line of the wake. Do they coincide with each other? Can anybody give me some explanation? Thanks!

 ramp July 6, 2005 15:31

Re: vortex formation length

I think these two are different things. In case of steady flow past circular cylinder, the wake length is defined as the distance between the center of cylinder (or rear stagnation point of the cylinder) and the point on the symmetry line at which U=V=0. I have not come up with the other definition but I guess it might be used to define the wake length in case of unsteady flow. You can get more detail on this subject in the following books:

1. Zdravkovich, M. M. (1997). Flow around circular cylinder Volume 1, Fundamentals. Oxford University Press, New York, USA.

2. Zdravkovich, M. M. (2003). Flow around circular cylinder Volume 2, Applications. Oxford University Press, New York, USA.

 fpz July 6, 2005 22:56

Re: vortex formation length

Thanks very much! I have got three methods to define the vortex formation length from the papers. These are: (1) the mean U=0 position on the symmetry line of the wake; (2) the maximum fluctuating u position and (3) the maximum vortex position. Can you give more explanation for the defination in terms of its usage? In fact it may be difficulty for me to get your recommanded books.Thanks again!

 ramp July 7, 2005 12:53

Re: vortex formation length

You can get the detailed information of vortex formation and length in the frist 3-4 pages of the following paper: C. H. K. Williamson, Vortex dynamics in the cylinder wake, Annual Reviews of Fluid Mechanics, Vol. 28, pp. 477-539, 1996. If you can not find this paper, please let me know. I'll write about these things in detail or I can forward you a copy of it.

 fpz July 8, 2005 00:22

Re: vortex formation length

You are great! I am sorry to say that I can not find this paper. I would like to get an e-copy of it or you can write more information about this question. Best regards!

 ramp July 8, 2005 10:15

Re: vortex formation length

[1] In the steady flow regime, the wake behind the cylinder is symmetric and closed. In this case, if the solution is steady, the 'recirculation or wake length' is defined as distance between the rear stagnation point or center of the cylinder and the point on the symmetry line having U=V=0. In case of the unsteady solution in this flow regime, its defined with the point on the symmetry line having mean U=V=0 and it is called as 'mean recirculation length'.

[2] In the steady periodic flow regime, the vortex is neither closed nor symmetric. In this case the maximum fluctuating u position is used to defined the vortex length.

[3] I am not sure about the third definition but I guess it might be defining the vortex position in unsteady flows.

If you still need to read more about it, I'll send you scaned copy of first 3-4 pages of that review paper by Williamson, let me know about it with ur e-mail id but it might take bit time.

 fpz July 8, 2005 20:28

Re: vortex formation length

Thanks. Please send me the first 3-4 pages copy of that review. By the way, I have the e-copy review paper(2004) by Williamson. If you need it, please tell me.

My email adress: mefpz@sina.com Thanks again! Pingzhi Fang, Tongji University, Shanghai, P. R. of China.

 fpz July 8, 2005 20:30

Re: vortex formation length

P.S. Please divided the copy several parts, for the attachment of my email is limited to 10M

 bestniaz October 1, 2015 01:36

Quote:
 Originally Posted by ramp ;35641 I think these two are different things. In case of steady flow past circular cylinder, the wake length is defined as the distance between the center of cylinder (or rear stagnation point of the cylinder) and the point on the symmetry line at which U=V=0. I have not come up with the other definition but I guess it might be used to define the wake length in case of unsteady flow. You can get more detail on this subject in the following books: 1. Zdravkovich, M. M. (1997). Flow around circular cylinder Volume 1, Fundamentals. Oxford University Press, New York, USA. 2. Zdravkovich, M. M. (2003). Flow around circular cylinder Volume 2, Applications. Oxford University Press, New York, USA.
Thanks for your response.. Although this is very old post... but I am really looking for these books,,,if you can provide, please email me at n_bkhan@yahoo.com...