CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Main CFD Forum

Oscillating cylinder

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 5, 2006, 01:28
Default Oscillating cylinder
  #1
MC
Guest
 
Posts: n/a
Hi,

I am calculating the oscillating cylinder problem in 2D domain with STAR-CD. I compared the results from different methods, such as velocity inlet, momentum source and moving grids. But, It was found that the results are different except the time that the maximum X-direction force appears. Do I have to add some added mass component ? Please help me !
  Reply With Quote

Old   September 5, 2006, 07:50
Default Re: Oscillating cylinder
  #2
Mani
Guest
 
Posts: n/a
Describe your problem in more detail.

Does the cylinder perform forced oscillations or is it suspended on a spring and free to oscillate, or something else...?

Describe the motion of the cylinder. (tranverse to the flow direction or in line, or both).

"Results are different" <-- what does that mean? What is different from what? You numerical results differ from experimental data, or from other numerical data...? How are they different?

What are the important parameters (e.g. Reynolds number, mass ratio, structural damping)?

Have you tried the case of vortex shedding over the stationary cylinder at that same Reynolds number? You should.

Let's start with that, and add anything else you can tell us about the case.

  Reply With Quote

Old   September 5, 2006, 09:32
Default Re: Oscillating cylinder
  #3
MC
Guest
 
Posts: n/a
Thank you very much for your comment!

Yes, I had to describe my problem more detail. The cylinder is under forced oscillations in line direction of flows. And I meant that the difference is magnitude of in-line force (such as drag component). The Reynolds number is above 10^6 and there is no structural damping. I tried to calculate the velocity profiles with different methods as I mentioned. The results are almost same. But the in-line forces are different. Actually considering a moving obstacle with constant speed, we treat the problem as a stationary body with moving flows. But, in case of oscillation body this is not a stationary problem. My question is how To compare the results between computation and experiment.
  Reply With Quote

Old   September 5, 2006, 18:22
Default Re: Oscillating cylinder
  #4
MC
Guest
 
Posts: n/a
In my previous meassage, the velocity profiles with different methods were calculated without the cylinder. In that case, the results are almost same.
  Reply With Quote

Old   September 6, 2006, 07:05
Default Re: Oscillating cylinder
  #5
Mani
Guest
 
Posts: n/a
Before you perform the computations with cylinder motion you should try the case with a stationary cylinder (at constant velocity). How well do you predict the drag in that case, as compared to experiments?
  Reply With Quote

Old   September 6, 2006, 21:41
Default Re: Oscillating cylinder
  #6
CH
Guest
 
Posts: n/a
Hi,

i'm also doing oscillating cylinder. however, mine is a tranverse case and i'm using immersed boundary. problem arises when the cylinder starts oscillating. the cl plot is not smooth and has lots of sudden up/down.

i've verfied with stationary and also rotating cylinder and the result's are similar.

is there an intermediate step which i can advance to before going to the oscillating problem? i'm trying to detect the error step by step...
  Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Oscillating Cylinder in Parallel Flow: Analytical Solution startingcfd Main CFD Forum 7 March 23, 2012 06:49
problem with oscillating cylinder ammi FLUENT 0 December 18, 2006 05:06
Interesting result from oscillating cylinder Wee Main CFD Forum 4 October 13, 2006 09:31
problem with oscillating cylinder zonexo FLUENT 3 September 14, 2006 10:13
UDF for oscillating cylinder fredD FLUENT 0 July 16, 2004 09:32


All times are GMT -4. The time now is 22:49.