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Beginner help, coordinate udf with output file

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Old   March 20, 2014, 04:16
Default Beginner help, coordinate udf with output file
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Hi, I am a beginner in both Fluent and C++.
I am trying to write a UDF for my project, it is a 2D axi-symmetric VOF model for a droplet impact; see link at the end of the post for the domain. The symmetry axis is my x axis and the wall my y axis.

The UDF will be used to calculate droplet height and the wall contact radius at every time step.
I need to find the coordinates of two cells at each time step. Both cells will have a volume fraction of between 0 and 1 (they lie at the interface).
One of the cells will have an x coordinate of 0, the other a y coordinate of 0.

The output file must contain the time step number, current time progressed, the x and then the y coordinates.

I am sure my UDF is not correct, I am unsure whether I have used suitable macros for the task, so would like advice on what I have not included or what needs changing.

If possible please can you explain in layman's terms.

Thanks in advance

#include "udf.h"
#include "mem.h"

DEFINE_PROFILE(xc, thread, position)
fp=fopen("data.txt","a"); /*opens file; data will be added on the end. 'a' stands for append*/
begin_c_loop_all(c,t); /*loops all cells*/
cell_t c0 = F_C0(f,t); /*sets desired volume fraction to 0.5, i.e. the interface cells*/
if (C_VOF(c0,t) = 0.5);
C_CENTROID(xc,c,t); /*find coordinate position of cell with desired volume fraction*/
if (xc[1] == 0 ); /*sets y coordinate equal to zero*/
x=xc[0]; /*names x coordinate*/
C_CENTROID(xc,c,t); /*find coordinate position of cell with desired volume fraction*/
if (xc[0] == 0 ); /*sets x coordinate equal to zero*/
y=xc[1]; /*names y coordinate*/
fprintf(fp,"Time Step %d", t, x, y); /*appends file with time step number, time, x coordinate and then y coordinate*/
end_c_loop_all(c,t); /*closes cell loop*/
fclose(fp); /*closes file*/
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2 dimensional, beginner, coordinate, output file, vof

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