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

how to calculate the drag force on a 3D sphere in OF?

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 5, 2015, 17:33
Default how to calculate the drag force on a 3D sphere in OF?
  #1
Senior Member
 
David Long
Join Date: May 2012
Location: Germany
Posts: 104
Rep Power: 13
keepfit is on a distinguished road
Hi Foamers,

I want to test the drag coefficient of regular (e.g. sphere) and irregular objects using the CFD method.

The problem is that how to calculate the fluid force acting the Object.

A still sphere is in the fluid and the velocity and pressure field are solved (currently pimpleFoam):



The resulting force would be: (assuming the sphere has N sub-surfaces, treated as wall)
Quote:
F_fluild = Sum(Pi * Ai* n), i = 1, 2, .... N
where Pi/AI- pressure/area of ith surface of the sphere/obstacle, n the normal of ith surface .

If we subtract buoyancy force Fb from F_fluid,
Quote:
F_(drag/life) = F_fluid - Fb
The issue is: how to loop on the certain boundary and access the pressure or velocity information on this boundary (object/obstacle).


Any tips or recommendation would be highly appreciated.

thanks in advance!

Last edited by keepfit; May 5, 2015 at 20:00.
keepfit is offline   Reply With Quote

Old   May 6, 2015, 06:20
Default
  #2
Senior Member
 
Tom Fahner
Join Date: Mar 2009
Location: Breda, Netherlands
Posts: 633
Rep Power: 31
tomf will become famous soon enoughtomf will become famous soon enough
Send a message via MSN to tomf Send a message via Skype™ to tomf
I would suggest to use the forces and forceCoeffs functionObjects. There are many threads on this forum that discuss it....
tomf is offline   Reply With Quote

Old   May 6, 2015, 13:04
Default
  #3
Senior Member
 
David Long
Join Date: May 2012
Location: Germany
Posts: 104
Rep Power: 13
keepfit is on a distinguished road
Quote:
Originally Posted by tomf View Post
I would suggest to use the forces and forceCoeffs functionObjects. There are many threads on this forum that discuss it....
thanks tomf, I will give a try on the library fucntions.
keepfit is offline   Reply With Quote

Reply

Tags
drag coefficient, sphere falling

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
Force vectors for drag during sweeping motion aamer FLUENT 0 April 18, 2011 09:17
Drag force on scaled models. arunjingade Main CFD Forum 6 July 1, 2010 09:54
How to calculate the drag force? James CFX 1 April 24, 2008 01:59
CFX analysis of a sphere - drag too low Rob Findlay CFX 6 March 26, 2007 11:11
Airfoil Drag Force wowakai Main CFD Forum 3 October 13, 1998 20:27


All times are GMT -4. The time now is 10:51.