How can I impose variable boundary conditions?

behrang2009 · December 18, 2009, 15:53

Hi Guys!
How can I define variable boundary conditions such as variable temperature on a wall? I believe that I should use UDF. Which parts of the UDF Manual help me most. Any hint?
Thanks
Good luck

dahu007 · December 18, 2009, 19:43

That's right you have ti write an UDF :
I used to do it with the velocity but it should be the same with the temperature. This is an example of a UDF of an unsteady velocity (you can find it in the UDF user guide of Fluent) (in the part boundary counditions and details UDF examples)

/************************************************** ********************
unsteady.c
UDF for specifying a transient velocity profile boundary condition
************************************************** *********************/
#include "udf.h"
DEFINE_PROFILE(unsteady_velocity, thread, position)
{
face_t f;
real t = CURRENT_TIME;
begin_f_loop(f, thread)
{
F_PROFILE(f, thread, position) = 20. + 5.0*sin(10.*t);
}
end_f_loop(f, thread)

}

When your UDF is written you have just to interpret it in Fluent !!!

behrang2009 · December 20, 2009, 20:26

Thanks man.
I have started reading UDF Manual

December 18, 2009, 15:53	How can I impose variable boundary conditions?	#1
behrang2009 Member Behrang Asgharian Join Date: Oct 2009 Posts: 38 Rep Power: 16	Hi Guys! How can I define variable boundary conditions such as variable temperature on a wall? I believe that I should use UDF. Which parts of the UDF Manual help me most. Any hint? Thanks Good luck

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
mass flow in is not equal to mass flow out	saii	CFX	12	March 19, 2018 05:21
CFX doesn't continue calculation...	mactech001	CFX	6	November 15, 2009 21:25
what's wrong with my Robin boundary conditions?	hadesmajesty	Main CFD Forum	0	September 23, 2009 04:57
Pressure boundary conditions	Lionel S.	Main CFD Forum	1	August 24, 2007 18:03
Help with boundary conditions	Dan	CFX	0	April 3, 2006 11:32

December 18, 2009, 19:43		#2
dahu007 New Member matth Join Date: Aug 2009 Posts: 8 Rep Power: 16	That's right you have ti write an UDF : I used to do it with the velocity but it should be the same with the temperature. This is an example of a UDF of an unsteady velocity (you can find it in the UDF user guide of Fluent) (in the part boundary counditions and details UDF examples) /************************************************ **************** unsteady.c UDF for specifying a transient velocity profile boundary condition ********************************************** ******************/ #include "udf.h" DEFINE_PROFILE(unsteady_velocity, thread, position) { face_t f; real t = CURRENT_TIME; begin_f_loop(f, thread) { F_PROFILE(f, thread, position) = 20. + 5.0sin(10.*t); } end_f_loop(f, thread) } When your UDF is written you have just to interpret it in Fluent !!!

December 20, 2009, 20:26		#3
behrang2009 Member Behrang Asgharian Join Date: Oct 2009 Posts: 38 Rep Power: 16	Thanks man. I have started reading UDF Manual