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

3D Velocity profile

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

Reply
 
LinkBack Thread Tools Display Modes
Old   November 4, 2007, 14:15
Default 3D Velocity profile
  #1
Shamoon
Guest
 
Posts: n/a
Hi everyone, I am doing 3d analysis of pipe flow. I want to use a UDF for 3d Velocity Profile of Turbulent flow. Can anybody help me how to make that UDF. I found UDF but only for 2d. Thanks
  Reply With Quote

Old   November 5, 2007, 02:46
Default Re: 3D Velocity profile
  #2
Sujay S
Guest
 
Posts: n/a
Two thing you can do

(1) directly write out the profile and apply

(2) or you can write the radial averaged axial vel profile through TUI. and curve fit it to the best polynomial then you can write a UDF using that polynomial function.

cheers Sujay S
  Reply With Quote

Old   November 5, 2007, 13:57
Default Re: 3D Velocity profile
  #3
Shamoon
Guest
 
Posts: n/a
yes, you are right but the problem is not for the polynomial, the problem is with the 3d geometry! I wnt to use the velocity profile at the pipe inlet. So i ahve to use a 3d profile. Whatever profiles I have seen are for 2D. If we have a parabolic velocity profile in 2D it will be Parabolied in 3D
  Reply With Quote

Old   November 6, 2007, 01:24
Default Re: 3D Velocity profile
  #4
Sujay S
Guest
 
Posts: n/a
I got your point. I feel that you can write out the profile from that location and apply to the inlet. It will automatically take care of 3D (i.e. x,y,z co-ordinate values.
  Reply With Quote

Old   November 7, 2007, 02:25
Default Re: 3D Velocity profile
  #5
Shamoon
Guest
 
Posts: n/a
Not clear please specify "....you can write out the profile from THAT location and apply to the inlet..." and explain
  Reply With Quote

Old   November 7, 2007, 02:43
Default Re: 3D Velocity profile
  #6
Sujay S
Guest
 
Posts: n/a
from where u r getting the profile data? experimental or u r going to run a case similar to u r s and gonna get a profile to apply to the actual case?
  Reply With Quote

Old   November 7, 2007, 05:34
Default Re: 3D Velocity profile
  #7
Emad
Guest
 
Posts: n/a
Hello you can 3D velocity profile inter data by using fllowing step2; 1. after read your case and run this case in constant velosity inlet. 2. Go to file -->write--> profile select inlet face and choose velocity save date in new file you can write any name 3. open this file for example microsoft excel 4. you can change velocity value you need inpou at inlet face. with ragerds emad
  Reply With Quote

Old   November 7, 2007, 05:37
Default Re: 3D Velocity profile
  #8
Emad
Guest
 
Posts: n/a
Hello you can 3D velocity profile inter data by using fllowing step2; 1. after read your case and run this case in constant velosity inlet. 2. Go to file -->write--> profile select inlet face and choose velocity save date in new file you can write any name 3. open this file for example microsoft excel 4. you can change velocity value you need inpou at inlet face. 5. go to file --> read --> profile then select your file with ragerds emad
  Reply With Quote

Old   November 8, 2007, 12:18
Default Re: 3D Velocity profile
  #9
Shamoon
Guest
 
Posts: n/a
I Want to get a profile and apply to the actual case. Actually I am comparing with some experimental data and in that they have a fully developed flow at the inlet. So i want to use that profile at he inlet. The vel profile normally given as

V=U(1-(r/R)^2) -----------> for 2D but which cordiante wil be there in formaula to tell the FLUENT that profile is 3D. I hope u got my point!!! Thanks
  Reply With Quote

Old   November 8, 2007, 13:14
Default Re: 3D Velocity profile
  #10
emad
Guest
 
Posts: n/a
hello apply inlet velocity at data type no profile. But you can used appley velocity profile to generate velocity data by using any programs. with best regarts

  Reply With Quote

Old   November 19, 2007, 23:08
Default Re: 3D Velocity profile
  #11
ryan
Guest
 
Posts: n/a
This is a code that I created by modifying the 2d velocity profile example in the manual. I have a fully developed turbulent profile (logarithmic), but you'll see what you have to do to make it 3d.

You establish a variable r and in my case y and z (inlet is in y-z plane and pipe axis is on the x-axis). Then use y and z to compute the variable r.

DEFINE_PROFILE(penstock_inlet_velocity,t,i)

{

real y,x[ND_ND], rad;

real z;

face_t f;

begin_f_loop(f,t)

{

F_CENTROID(x,f,t);

y = x[1];

z = x[2];

rad = pow(y*y+z*z,0.5);

F_PROFILE(f,t,i) = Ucent*pow(1-rad/RAD,N);

}

end_f_loop(f,t)

}
  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
[UDF] Relative coordinates in logarithmic velocity profile cfdworker Fluent UDF and Scheme Programming 24 February 23, 2015 05:33
Logarithmic velocity profile cfdworker Fluent UDF and Scheme Programming 0 April 23, 2009 19:09
[boundary condition] logarithmic velocity profile cfdworker FLUENT 2 April 17, 2009 23:36
Prescribed inflow velocity profile - how to? Alan Main CFD Forum 10 October 28, 2005 12:14
Terrible Mistake In Fluid Dynamics History Abhi Main CFD Forum 12 July 8, 2002 09:11


All times are GMT -4. The time now is 07:07.