CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > Siemens > STAR-CCM+

Wake length behind a circular cylinder

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree2Likes
  • 1 Post By triple_r
  • 1 Post By triple_r

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 8, 2013, 14:04
Default Wake length behind a circular cylinder
  #1
New Member
 
Elham
Join Date: Jun 2013
Location: Germany
Posts: 8
Rep Power: 12
Corleone84 is on a distinguished road
Hello guys.
I'd like to calculate the Wake length behind a circular cylinder for Reynolds number 40 (2D Geometry,laminar, steady) in Star ccm +. My Drag coefficient is 1.1864 . How can i calculate the Wake length in Star ccm? I know,the Length of the Wake is, Lw is defined as the streamwise distance between the confluence point (wake stagnation point) and the rear stagnation point of the cylinder.
Thanks!
Corleone84 is offline   Reply With Quote

Old   October 8, 2013, 16:41
Default
  #2
Senior Member
 
Reza
Join Date: Mar 2009
Location: Appleton, WI
Posts: 116
Rep Power: 17
triple_r is on a distinguished road
Won't plotting u_x on the center-line behind the cylinder and looking for a sign change work?
bestniaz likes this.
triple_r is offline   Reply With Quote

Old   December 29, 2015, 06:02
Default
  #3
Member
 
N B Khan
Join Date: Jan 2014
Posts: 39
Rep Power: 12
bestniaz is on a distinguished road
Quote:
Originally Posted by triple_r View Post
Won't plotting u_x on the center-line behind the cylinder and looking for a sign change work?
I calculated the re circulation length successfully,,, thanks

But how to calculate the other parameters as mention the figure, Sc, Bw etc.. plz
bestniaz is offline   Reply With Quote

Old   December 29, 2015, 11:37
Default
  #4
Senior Member
 
Reza
Join Date: Mar 2009
Location: Appleton, WI
Posts: 116
Rep Power: 17
triple_r is on a distinguished road
The easiest way that I can think of is using: Line Integrated Convolution.

To use this, create a vector scene for velocity, select the vector display and change its display mode from glyph to Line Integrated Convolution.

You should see a very nice plot of a bunch of mini streamlines. You can control the display by changing the options under line integrated convolution if you expand the vector plot. Increase the "number Steps" to get longer streamlines, and have a large (for example 0.7) blending factor so you can actually see the lines. Then you should be able to just see a plot like the one in the first post, and you can use the ruler (distance report) tool to measure distances.

In the attached figure I've used the symmetry to just solve for half of the domain, and the line is not exactly vertical, but in the output window star reports all three components of the distance:

Code:
Distance Report
  Distance = 0.16684 (m)
  Coordinate System : Laboratory
  Node Point p1 : [ 0.71210 0.16622 0.0000 ]
  Node Point p2 : [ 0.72646 0.0000 0.0000 ]
  Components
    d(X) = 0.014365 (m)
    d(Y) = -0.16622 (m)
    d(Z) = 0.0000 (m)
so the distance s, for example, is going to be 2 x 0.166 = 0.332.

I hope this helps.
Attached Images
File Type: jpg recirc.jpg (48.2 KB, 50 views)
triple_r is offline   Reply With Quote

Old   December 30, 2015, 00:21
Default
  #5
Member
 
N B Khan
Join Date: Jan 2014
Posts: 39
Rep Power: 12
bestniaz is on a distinguished road
Quote:
Originally Posted by triple_r View Post
The easiest way that I can think of is using: Line Integrated Convolution.

To use this, create a vector scene for velocity, select the vector display and change its display mode from glyph to Line Integrated Convolution.

You should see a very nice plot of a bunch of mini streamlines. You can control the display by changing the options under line integrated convolution if you expand the vector plot. Increase the "number Steps" to get longer streamlines, and have a large (for example 0.7) blending factor so you can actually see the lines. Then you should be able to just see a plot like the one in the first post, and you can use the ruler (distance report) tool to measure distances.

In the attached figure I've used the symmetry to just solve for half of the domain, and the line is not exactly vertical, but in the output window star reports all three components of the distance:

Code:
Distance Report
  Distance = 0.16684 (m)
  Coordinate System : Laboratory
  Node Point p1 : [ 0.71210 0.16622 0.0000 ]
  Node Point p2 : [ 0.72646 0.0000 0.0000 ]
  Components
    d(X) = 0.014365 (m)
    d(Y) = -0.16622 (m)
    d(Z) = 0.0000 (m)
so the distance s, for example, is going to be 2 x 0.166 = 0.332.

I hope this helps.
Thanks dear for your response...
But I am using the Fluent and in fluent I could not find anything related to "glyph to Line Integrated Convolution."....
bestniaz is offline   Reply With Quote

Old   December 30, 2015, 11:15
Default
  #6
Senior Member
 
Reza
Join Date: Mar 2009
Location: Appleton, WI
Posts: 116
Rep Power: 17
triple_r is on a distinguished road
Sorry, saw this in StarCCM+ forum, so thought you are using that. I don't have access to FLUENT, so can't help a lot, but FLUENT should have a tool to generate streamlines. Usually they ask for a starting point/line/plane for the streamlines. instead of using the inlet for the starting seed, create a line/plane that cuts through the recirculation zone and you should get what you wanted. You'll need to change the number of seed points to get the edge of the recirculation zone though.

Another way is to plot the normal-to-plane component of vorticity and try to find the zeroeth contour (for edge) and maximum (for the "eye"), but because of walls, I don't know if you are going to get a detailed enough picture from this.

Good luck.
bestniaz likes this.
triple_r is offline   Reply With Quote

Old   December 31, 2015, 02:10
Default
  #7
Member
 
N B Khan
Join Date: Jan 2014
Posts: 39
Rep Power: 12
bestniaz is on a distinguished road
Quote:
Originally Posted by triple_r View Post
Sorry, saw this in StarCCM+ forum, so thought you are using that. I don't have access to FLUENT, so can't help a lot, but FLUENT should have a tool to generate streamlines. Usually they ask for a starting point/line/plane for the streamlines. instead of using the inlet for the starting seed, create a line/plane that cuts through the recirculation zone and you should get what you wanted. You'll need to change the number of seed points to get the edge of the recirculation zone though.

Another way is to plot the normal-to-plane component of vorticity and try to find the zeroeth contour (for edge) and maximum (for the "eye"), but because of walls, I don't know if you are going to get a detailed enough picture from this.

Good luck.
Thank you so much,,,,
I did it successfully... Once again thanks.
Best Regards
Niaz
bestniaz is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
benchmark: flow over a circular cylinder goodegg Main CFD Forum 12 January 22, 2013 12:47
Experimental data from far wake behind a circular cylinder Heini Main CFD Forum 0 October 13, 2011 07:30
Very small recirculation length for flow over a circular cylinder Tarak OpenFOAM Running, Solving & CFD 2 August 31, 2011 12:27
asking about wake in Inviscid flow in cylinder circular teguhtf FLUENT 0 April 23, 2011 01:14
Formation length in the wake of a circular cylinder Chengwang Lei Main CFD Forum 2 April 24, 1999 04:42


All times are GMT -4. The time now is 09:22.