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-   -   udf begin_c_loop problems (http://www.cfd-online.com/Forums/fluent/42404-udf-begin_c_loop-problems.html)

Abigail September 27, 2006 09:41

udf begin_c_loop problems
 
I am trying to write a udf in order to count the number of cells within a certain zone in my domain. I will then input a source in this zone the value of which will depend on the number of cells. I am doing this because I want to make sure I get the same source value in different zones that will have different number of cells (it is a tetrahedral grid.).

My main question/problems are:

1) Have I understood correctly in thinking the udf will put the source value in at each cell.

2) How does the fluent macro begin_c_loop….end_c_loop work. I was hoping to use it to loop through the cells to count the number in my zone and then use a second loop to input the source value but this does not seem to work. How can I get it to move out of the first loop?

3)I have pasted my code below. I put in a print to screen command at the end of the first loop counting cells to check what was happening. All that happens when I run this is it prints out the number of cells, and keeps adding to them and printing them out. When I compile I get several warnings saying my x[1], x[2] are used uninitialised and for the final line it gives a warning "Control reaches end of non-void function."

Thanks for any help Abigail

#include "udf.h"

DEFINE_SOURCE(my_source, cell, thread, dS, eqn) { real x[3]; /* this will hold the position vector */ real source; real i; real no_of_cells; real Source_Quantity; real small_x_value,large_x_value,small_y_value,large_y_ value,small_z_value,large_z_value; small_x_value=2.08; large_x_value=2.18; small_y_value=1.10; large_y_value=1.20; small_z_value=1.625; large_z_value=1.725;

begin_c_loop(cell,thread)

{

C_CENTROID(x,cell,thread);

if ((small_x_value<=x[0])&(x[0]<=large_x_value))

{

if ((small_y_value<=x[1])&(x[1]<=large_y_value))

{

if((small_z_value<=x[2])&(x[2]<=large_z_value))

{

/* Find number of cells source is inputted over*/

i=1;

no_of_cells=no_of_cells+i;

}

else

{

}

}

else

{

}

}

else

{

}

}

end_c_loop(cell,thread)

printf("\n Numberofcells=%f\n",no_of_cells); /*print no of cells to screen for check*/

Source_Quantity=(500/(no_of_cells)); begin_c_loop(cell,thread)

{

C_CENTROID(x,cell,thread);

if ((small_x_value<=x[0])&(x[0]<=large_x_value))

{

if ((small_y_value<=x[1])&(x[1]<=large_y_value))

{

if((small_z_value<=x[2])&(x[2]<=large_z_value))

{

source=(Source_Quantity);

dS[eqn]=0;

}

else

{

source=0;

dS[eqn]=0;

}

}

else

{

source=0;

dS[eqn]=0;

}

}

else

{

source=0;

dS[eqn]=0;

} return source;

}

end_c_loop(cell,thread) }


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