CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > OpenFOAM

Flow past rotating cylinder: Problem with ForeCoeffs

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

LinkBack Thread Tools Search this Thread Display Modes
Old   December 14, 2013, 07:49
Default Flow past rotating cylinder: Problem with ForeCoeffs
New Member
Raphael Ouillon
Join Date: Oct 2013
Posts: 3
Rep Power: 12
raf1111 is on a distinguished road

I am currently studying the effects of a rotating cylinder in a low Reynolds uniform flow. I need to extract the lift and drag coefficients on the cylinder and I therefore use the forcecoeffs function. The problem is that in 3D simulations, the flow displays a spanwise instability along the cylinder. Since the drag and lift are integrated on the whole cylinder, the resulting Cd and Cl are not representative of the Cd and Cl at a specific location of the cylinder. The resulting drag and lift curves are indeed very noisy and random in appearance whereas the local drag and lift curve are expected to present a clear oscillation with a fixed Strouhal number.

My question is the following: Is it possible to extract the lift and drag curve at each spanwise location along the cylinder using ForceCoeffs instead of the average lift and drag? If not, is it possible to create a "line" patch at a given location and to compute the forces on this patch instead of on the whole cylinder patch?

I hope my problem is clear and if not, please tell me and I'll of course provide more information. Thank you very much in advance for your help!

raf1111 is offline   Reply With Quote

Old   December 16, 2013, 09:45
Senior Member
Join Date: Dec 2010
Posts: 135
Rep Power: 15
eRzBeNgEl is on a distinguished road
I had this issue a few weeks ago and did solved it by postprocessing: here are my steps in short

These are my paraviewsteps in short:

1)Extracted Surface
2)Generate Surface Normals
cp = normals*(p2-p1); ->Pressure Drag
cf=tangentials*mu*wallGradU_y -> Friction Drag (or calculated directly by foamCalc components wallGradU
4) Build Integral Drag=S(cp_X+cf_X)dA*2/rho*v*v*A

Hope this helps, but there are some differences to OpenFoam Output -> could be caused by building derivates or integration failures
eRzBeNgEl is offline   Reply With Quote


forcecoeffs, lift and drag, openfoam

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
Rotating cylinder in uniform flow: Which BC for U? raf1111 OpenFOAM Pre-Processing 3 October 13, 2013 06:35
Flow past a cylinder. Help needed Lurapa Main CFD Forum 1 August 18, 2013 11:25
FLUENT, flow past a circular cylinder Paul Reichl Main CFD Forum 16 December 8, 2012 15:21
free surface flow past cylinder vineet FLUENT 1 February 21, 2011 23:11
Flow past a rotating cylinder ddigrask OpenFOAM Running, Solving & CFD 4 July 18, 2008 11:02

All times are GMT -4. The time now is 10:05.