udf velocity profile
 

hi I am trying to write a udf function that use the index number in order to put a value from array. I wrote the following function that isn't working




for example the first y , index=1 so u=A[1]=8;

thanks for the help

Are you sure that the range of c0 is in [0, 250] and at least one of these values are in [0,7] ? By the way, c language is zero-based so that A[0] = 8 and A[1] = 7.

yes
 

at my grid the velocity inlet border is the line x=0, -0.01<y<0.01 and I have 251 points on the line

Try this:
#include"udf.h" DEFINE_PROFILE(unsteady_velocity, thread, position) {
real x[ND_ND]; /* this will hold the position vector */
real y;real A[251]={8,7,6,5,4,3,2,1};
real t = CURRENT_TIME;
face_t f;
int ind;
begin_f_loop(f, thread) {
F_CENTROID(x,f,thread);
c0 = F_C0(f,thread);
y = 250*(x[1]*50+0.5);
ind = (int) (y+0.5);
F_PROFILE(f, thread, position) =A[ind];
}
end_f_loop(f, thread)
}

...
 

my problem is that my grid is note uniform, there is a why to know the index from the grid?


thanks for the help

It is easy to hard-coded your udf file. Print the value of c0. If the value of c0 is contiguous then shift the value so that c0 is in the range [0,250]. Or

#include"udf.h" DEFINE_PROFILE(unsteady_velocity, thread, position) {
real x[ND_ND]; /* this will hold the position vector */
real y;real A[251]={8,7,6,5,4,3,2,1};
real t = CURRENT_TIME;
face_t f;
int ind=0;
begin_f_loop(f, thread) {
F_CENTROID(x,f,thread);
c0 = F_C0(f,thread);
F_PROFILE(f, thread, position) =A[ind++];
}
end_f_loop(f, thread)
}

if the values of array A is assigned according to its appearance in the thread loop.

when i wrote the code
 

it was written to me the following message will running :

Divergence detected in AMG solver: x-momentum


thanks for the help