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Old   May 20, 2013, 14:47
Unhappy udf velocity profile
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hilla tor
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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

Code:
#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; begin_f_loop(f, thread) { F_CENTROID(x,f,thread); c0 = F_C0(f,thread); y = x[1]*2000; F_PROFILE(f, thread, position) =A[c0];} end_f_loop(f, thread)}



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

thanks for the help
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Old   May 21, 2013, 01:13
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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.
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Old   May 21, 2013, 15:23
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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
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Old   May 21, 2013, 20:46
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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)
}
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Old   May 21, 2013, 22:51
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my problem is that my grid is note uniform, there is a why to know the index from the grid?


thanks for the help
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Old   May 21, 2013, 23:28
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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.
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Old   May 23, 2013, 12:10
Default when i wrote the code
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it was written to me the following message will running :

Divergence detected in AMG solver: x-momentum


thanks for the help
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