[sarbakhshian]

Hello i'm trying to write a UDF for this two inlet BCs:
(1.5*4/0.1681)*y*(0.41-y)*(0.5*(1-cos(0.5*Pi*t))) if t<2sec
(1.5*4/0.1681)*y*(0.41-y) otherwise


the UDF i have wrote is like below but it doesn't work correctly because i get the velocity vector like the picture i have attached, and the velocity shouldn't be like that after 2 seconds:



/************************************************** *********************
UDF for specifying transient velocity profile boundary condition
************************************************** **********************/

#include "udf.h"

#define H 0.41
#define PI 3.14

DEFINE_PROFILE(inlet_velocity, thread, index)
{
real x[ND_ND]; /* this will hold the position vector */
real y;
face_t f;

begin_f_loop(f, thread) /* loops over all faces in the thread passed in the DEFINE macro argument */

{
F_CENTROID(x, f, thread);
y = x[1];
{
if(CURRENT_TIME<2)
F_PROFILE(f, thread, index) =((1.5*1)*(4/0.1681)*y*(H-y))*((1-cos(PI*CURRENT_TIME/2))/2);
}
{
if(CURRENT_TIME>=2)
F_PROFILE(f, thread, index) =((1.5*1)*(4/0.1681)*y*(H-y));
}
}
end_f_loop(f, thread)
}

[AlexanderZ]

try this code

/************************************************** ********************* 
UDF for specifying transient velocity profile boundary condition 
************************************************** **********************/

#include "udf.h"

#define H 0.41
#define PI 3.14

DEFINE_PROFILE(inlet_velocity, thread, index)
{
real x[ND_ND]; /* this will hold the position vector */
real y;
real time;
face_t f;
time = CURRENT_TIME;
begin_f_loop(f, thread) /* loops over all faces in the thread passed in the DEFINE macro argument */

{
F_CENTROID(x, f, thread);
y = x[1];
{
if(time<2)
F_PROFILE(f, thread, index) =((1.5*1)*(4/0.1681)*y*(H-y))*((1-cos(PI*time/2))/2);
}
{
if(time>=2)
F_PROFILE(f, thread, index) =((1.5*1)*(4/0.1681)*y*(H-y));
}
}	
end_f_loop(f, thread)
}

best regards