CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Fluent UDF and Scheme Programming

impose same velocity at inlet

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

Like Tree2Likes
  • 1 Post By flotus1
  • 1 Post By flotus1

Reply
 
LinkBack Thread Tools Display Modes
Old   July 29, 2013, 12:36
Default impose same velocity at inlet
  #1
Member
 
rayan
Join Date: Jun 2013
Posts: 65
Rep Power: 4
rayan24 is on a distinguished road
I want to impose by UDF a same velocity profile in 3 inlets, but i don't get same velocity in the 3 inlets apparently i impose my profile in function of the distance r!!

how can i impose my velocity profile in the "surface" of inlet to get samevelocity please??

my udf is :
include "udf.h"
Quote:
DEFINE_PROFILE(z_velocity_inlet,t,i)
{ real x[ND_ND]=3;
real r;
face_t f;
begin_f_loop(f,t)
{ F_CENTROID(x,f,t);
r = x[0];
F_PROFILE(f,t,i) = -((0.0431*pow(r,3))-(0.3857*pow(r,2))+(0.3129*r)+8.8045);
} end_f_loop(f,t)
Thanks
rayan24 is offline   Reply With Quote

Old   July 29, 2013, 14:14
Default
  #2
Senior Member
 
flotus1's Avatar
 
Alex
Join Date: Jun 2012
Location: Germany
Posts: 1,107
Rep Power: 19
flotus1 will become famous soon enoughflotus1 will become famous soon enough
Apparently, you are using the absolute value of the x-coordinate for each of the 3 inlets. If they dont have identical position, the velocity will be different.
I already tried to point this out in your last thread concerning this topic

Additionally, "real x[ND_ND]=3;" is some kind of strange.
You initialize the value 3 to the variable x here, which makes no sense as it is overwritten anyway. Use "real x[ND_ND];" instead.
rayan24 likes this.
flotus1 is offline   Reply With Quote

Old   July 30, 2013, 03:02
Default
  #3
Member
 
rayan
Join Date: Jun 2013
Posts: 65
Rep Power: 4
rayan24 is on a distinguished road
Thanks Alex for your replay,

I confirme that the inlets are diffrents coordinate of X, so how can i specify this difference in UDF please
rayan24 is offline   Reply With Quote

Old   July 30, 2013, 03:12
Default
  #4
Senior Member
 
flotus1's Avatar
 
Alex
Join Date: Jun 2012
Location: Germany
Posts: 1,107
Rep Power: 19
flotus1 will become famous soon enoughflotus1 will become famous soon enough
Write 3 similar UDFs and shift the coordinate to match the "local" coordinate system of each inlet.
Change the variable "offset" so that r actually becomes the distance (I suppose distance from the wall?) in each inlet.
Code:
r = x[0]-offset;
If you are having trouble with this, we will need a sketch of your setup and the velocity profiles you want in order to give further advice.
rayan24 likes this.
flotus1 is offline   Reply With Quote

Old   July 30, 2013, 03:26
Default
  #5
Member
 
rayan
Join Date: Jun 2013
Posts: 65
Rep Power: 4
rayan24 is on a distinguished road
Thank you very much Alex that's what I did , I needed your confirmation! its OK

but in the results of simulation I feel that the velocity is not properly difffuse ? (i use RSM model) do you have an idea ?
rayan24 is offline   Reply With Quote

Old   July 30, 2013, 04:07
Default
  #6
Senior Member
 
flotus1's Avatar
 
Alex
Join Date: Jun 2012
Location: Germany
Posts: 1,107
Rep Power: 19
flotus1 will become famous soon enoughflotus1 will become famous soon enough
I dont know what you mean by "the velocity is not properly diffuse".
flotus1 is offline   Reply With Quote

Old   July 30, 2013, 04:53
Default
  #7
Member
 
rayan
Join Date: Jun 2013
Posts: 65
Rep Power: 4
rayan24 is on a distinguished road
It's okay, it was just a display problem

Thank you Alex for your answers and help
rayan24 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
Simulation of radial gas turbine, Inlet velocity components dmaz CFX 9 May 29, 2015 08:01
Reduced domain/ Pressure inlet to velocity inlet victoryv FLUENT 1 June 29, 2013 14:45
User Defined Profiles, Swirl, Velocity Inlet saurus FLUENT 0 January 26, 2011 16:35
UDF problem : inlet velocity in cyl. coord. system Jongdae Kim FLUENT 0 June 15, 2004 11:21
what the result is negatif pressure at inlet chong chee nan FLUENT 0 December 29, 2001 06:13


All times are GMT -4. The time now is 05:55.