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

[boundary condition] logarithmic velocity profile

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 17, 2009, 16:14
Default [boundary condition] logarithmic velocity profile
  #1
New Member
 
Join Date: Apr 2009
Posts: 14
Rep Power: 8
cfdworker is on a distinguished road
Hello, I have a problem that involves boundary condition in fluent. My boundary condition is a logarithmic velocity profile, that enters in the domain, and I don’t know how to do this in fluent. With velocity inlet I can create a regular velocity profile, but I can’t create a logarithmic velocity profile in boundary condition. So I wonder if anyone can tell me how I define a logarithmic velocity profile in boundary condition with fluent.

Thanks and sorry for my bad English

Last edited by cfdworker; April 17, 2009 at 17:33.
cfdworker is offline   Reply With Quote

Old   April 17, 2009, 17:40
Default
  #2
New Member
 
mark
Join Date: Apr 2009
Posts: 5
Rep Power: 8
redlemon is on a distinguished road
define a profile file and call the profile in the bc file or for more flexibility use a udf for spatial variation definition using log relationship. see udf guide and define profile macro for example.
redlemon is offline   Reply With Quote

Old   April 17, 2009, 23:36
Default
  #3
New Member
 
Join Date: Apr 2009
Posts: 14
Rep Power: 8
cfdworker is on a distinguished road
Hello, thanks for the answer. I tried to make an udf file, like you suggested, that defines the logarithmic profile, but when I interpreted or compiled the file, fluent report an error and can’t read the file. I wonder if the udf file I make is wrong. My udf is this file:

#include "udf.h"

DEFINE_PROFILE(inlet_x_velocity, thread, position)
{
real x[ND_ND];
real y;
face_t f;

begin_f_loop(f, thread)
{
F_CENTROID(x,f,thread);
y = x[1];
F_PROFILE(f, thread, position) = 3.*log(y/((10.)^(-2.)))/log(10./((10.)^(-2.)));
}
end_f_loop(f, thread)
}

My domain is 3d and my simulation consists in analyze the wind in a terrain. So I ask anyone if can tell me what is wrong with my udf file.

I would appreciate any suggestions.
cfdworker 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
3D UDF Paraboilc Velocity Profile (Can't Maintain) Sing FLUENT 9 November 26, 2014 08:58
maintaining a logarithmic velocity distribution Morten Andersen CFX 1 January 8, 2007 12:37
Prescribed inflow velocity profile - how to? Alan Main CFD Forum 10 October 28, 2005 12:14
Variables Definition in CFX Solver 5.6 R P CFX 2 October 26, 2004 02:13
create logarithmic wind profile for inlet Murat Main CFD Forum 0 December 30, 2003 01:45


All times are GMT -4. The time now is 13:29.