CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Pre-Processing

Rotating cylinder in uniform flow: Which BC for U?

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

Reply
 
LinkBack Thread Tools Display Modes
Old   October 12, 2013, 14:12
Post Rotating cylinder in uniform flow: Which BC for U?
  #1
New Member
 
Raphael Ouillon
Join Date: Oct 2013
Posts: 3
Rep Power: 5
raf1111 is on a distinguished road
Hello,

I am working on a semester project dealing with a uniform flow past a rotating cylinder (Re=200, solved using icoFoam).
I have tried to use the rotatingWallVelocty boundary condition for U but when I check the flow field at the end of the simulations, the velocity at the cylinder's surface is not constant (and therefore not equal to the radius times the angular velocity that I specified in the boundary condition for U).

I'm new at openFoam and I've tried to find the solution to this problem on other threads but without success so I need your help ! Do you know if there are basic mistakes/problems that need to be avoided when using this BC?

Please let me know if you need more information about my problem!

Thank you in advance for your help,

Raphael
raf1111 is offline   Reply With Quote

Old   October 12, 2013, 16:17
Default
  #2
ngj
Senior Member
 
Niels Gjoel Jacobsen
Join Date: Mar 2009
Location: Deltares, Delft, The Netherlands
Posts: 1,713
Rep Power: 27
ngj will become famous soon enoughngj will become famous soon enough
Hi Raphael,

I have just looked into the code of OF2.2.1. and it seems correct. The only thing I can thing of is the origin of your object. Are you sure that you have placed the origin in the centre of your object?

Kind regards

Niels
__________________
Please note that I do not use the Friend-feature, so do not be offended, if I do not accept a request.
ngj is offline   Reply With Quote

Old   October 13, 2013, 05:15
Default
  #3
New Member
 
Raphael Ouillon
Join Date: Oct 2013
Posts: 3
Rep Power: 5
raf1111 is on a distinguished road
Hello and thank you for your answer. I checked and the origin of the rotation does correspond to the center of the cylinder.
However, I did a slice on a plane normal to the axis of the cylinder, halfway through the z-direction of the domain, and it seems that I have the correct velocity around the cylinder. I think that my mistake comes from the boundary conditions applied on the side walls (connected to the cylinder's tips). I've tried using the slip BC and it looks like it somehow interferes with the velocity on the cylinder's surface right next to the side walls. This would actually explain why the BC on the cylinder is correct at the center of the domain but not on the side walls. I'll try to look in more details at the definition of the slip BC but otherwise I'll simply look at the flow at the center of the domain (which is probably the most relevant place to look actually).

Thanks again for your answer,

Raphael
raf1111 is offline   Reply With Quote

Old   October 13, 2013, 06:35
Default
  #4
ngj
Senior Member
 
Niels Gjoel Jacobsen
Join Date: Mar 2009
Location: Deltares, Delft, The Netherlands
Posts: 1,713
Rep Power: 27
ngj will become famous soon enoughngj will become famous soon enough
Hi Raphael,

A couple of things come to my mind:

1. You could start with a cyclic/periodic condition in the z-direction, which will remove your dependency on end effects.

2. Have you visualised the velocities at the cylinder surface, i.e. turning on the cylinder boundary in paraView/paraFoam? These should be correct. If you look at the near-wall cell, then you already start to get effects from other boundaries into the result.

3. Also, if you are using interpolated and not cell centred values, the picture you obtain can be distorted from the actual computed picture.

4. Finally, I have also been confused in the beginning with the default perspective in paraView/paraFoam. I always use parallel perspective, as it is otherwise difficult to see the correct behaviour along one axis, due to a natural perspective representation. You can change this in Edit->View Settings->General.

Good luck,

Niels
__________________
Please note that I do not use the Friend-feature, so do not be offended, if I do not accept a request.
ngj is offline   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
OpenFOAM solution is diverging for stress analysis in two-pahse microstructure. Sargam05 OpenFOAM 16 April 30, 2013 16:18
Need help with boundary conditions: open to atmosphere Wolle OpenFOAM 2 April 11, 2011 07:32
flow over rotating cylinder sridharmec ANSYS 0 November 19, 2010 00:55
RasInterFoam STRANGE RESULTS AT BOUNDARY kumar2 OpenFOAM Running, Solving & CFD 8 March 24, 2008 19:38
Validation of flow around rotating cylinder Marat Hoshim Main CFD Forum 1 October 10, 2000 13:09


All times are GMT -4. The time now is 03:20.