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

Cd calculation when velocity is varying with time

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 14, 2015, 05:25
Default Cd calculation when velocity is varying with time
  #1
Member
 
DongHo
Join Date: Jul 2013
Posts: 51
Rep Power: 13
eddykendo is on a distinguished road
Dear. Foamers

I am working on Cd calculation for the case of a changing velocity with the time using URANS with k-w SST (accelerated cylinder case). Actually, initial velocity 1 m/s and then, after 1 sec, 1 to 5 m/s, the velocity is linearly changing with a ramp profile until 2 sec, finally, 5 m/s will be kept until 6 sec.
For this case, how I can set up the value of "magUInf" in a file "forceCoeffs" even though I set up the velocity profile in "U"?
If the magnitude of velocity is not changing, "magUInf" is set to be initial velocity, though..

Please give me any advice if you have an experience like this.

Thanks
eddykendo is offline   Reply With Quote

Old   September 29, 2015, 20:36
Default
  #2
Member
 
Davi Barreira
Join Date: Apr 2014
Location: Fortaleza
Posts: 76
Rep Power: 12
davibarreira is on a distinguished road
Indeed the coefficients are calculated using a fixed velocity. You can set up a fixed velocity in the forceCoeffs dictionary (like 1m/s) and then postprocess the results with a programming language (or Excel) by recalculating the force coefficientes based on the new velocity. So:
Cd = 2*D/(rho*U^2)

If you put U = 1, then Cd' = 2*D/rho

In your forceCoeffs.dat you have time, so you can use to calculate your velocity at a given time. U = f(t)

Therefore, Cd = Cd'/(Ucalc^2)
davibarreira 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
Elastic or Plastic Deformations in OpenFOAM NickolasPl OpenFOAM Pre-Processing 36 September 23, 2023 09:22
Extrusion with OpenFoam problem No. Iterations 0 Lord Kelvin OpenFOAM Running, Solving & CFD 8 March 28, 2016 12:08
Star cd es-ice solver error ernarasimman STAR-CD 2 September 12, 2014 01:01
Time varying velocity BC tejasvikrishna FLUENT 3 March 22, 2011 14:41
time varying inlet velocity Zhe Liu CFX 0 July 31, 2008 07:56


All times are GMT -4. The time now is 14:40.