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-   -   Time varying velocity BC (https://www.cfd-online.com/Forums/fluent/86427-time-varying-velocity-bc.html)

tejasvikrishna March 22, 2011 11:29
Time varying velocity BC
 
Hello,
I need a sinusoidal time varying UDF for my problem , I am kind of new to fluent , please direct me , any time varying BC tutorial is helpful but couldnt find any on google
Thankyou
Tejasvi

Amir March 22, 2011 12:27
Hi,
if you are new in UDF, it will be better to use other ways like defining a profile.
refer to: <defining transient boundary conditions> in user guide (7.1.9 in FLUENT 6.3.26)

tejasvikrishna March 22, 2011 13:06
thanks for the reply, I will try that out , meanwhile I have written an UDF , does this look reasonable

#include "udf.h"

DEFINE_PROFILE(transient_velocity, thread, position)
{

float t, velocity;
face_t f;

t = RP_Get_Real("flow-time");

velocity = Sin(40*3.14*t);

begin_f_loop(f, thread)
{
F_PROFILE(f, thread, position) = velocity;
}
end_f_loop(f, thread)

Amir March 22, 2011 13:41
it needs some changes:
Quote:
#include "udf.h"
#include "math.h"
DEFINE_PROFILE(transient_velocity,thread,position)
{
face_t f;
float t, velocity;
t = CURRENT_TIME;
velocity = sin(40*3.14*t);//argument should be in radian
begin_f_loop(f, thread)
{
F_PROFILE(f, thread, position) = velocity;
}
end_f_loop(f, thread)
}


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