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UDF print results into .dat file more than once per time step? how to fix it?

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Old   April 26, 2019, 10:38
Default UDF print results into .dat file more than once per time step? how to fix it?
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xuwenhua
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fluent 19.2 , UDF in parallel
Using Compute_Force_And_Moment micro to calculate the force of a flapping foil, then printing the results into a .dat file. I found that the UDF output the same results into the .dat file 1~3 times per time step, so how can I fix the problem to print the same results in the .dat file only once in every timestep?

Thanks!
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Old   April 26, 2019, 21:18
Default Another solution
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I find MATLAB ‘unique’ function can solve the problem~~
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Old   April 27, 2019, 04:40
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I don't understand the problem. Do you mean that you have more iteration per time step and you want to print the results just for the last iteration of each time step? In this case you can use DEFINE_EXECUTE_AT_END macro and print from there.



If the problem is that you are working in parallel and fluent is printing the results for each node then you can try to add something like this:


FILE *try;
#ifPARALLEL
if(I_AM_NODE_ZERO_P)
#endif
{
try=fopen("youfile.dat","w+");
fprintf(try, ....... );
fclose(try);
}
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Old   April 27, 2019, 21:32
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Quote:
Originally Posted by pianaCFD View Post
I don't understand the problem. Do you mean that you have more iteration per time step and you want to print the results just for the last iteration of each time step? In this case you can use DEFINE_EXECUTE_AT_END macro and print from there.



If the problem is that you are working in parallel and fluent is printing the results for each node then you can try to add something like this:


FILE *try;
#ifPARALLEL
if(I_AM_NODE_ZERO_P)
#endif
{
try=fopen("youfile.dat","w+");
fprintf(try, ....... );
fclose(try);
}
thanks! I'll have a try.
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Old   April 29, 2019, 01:31
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you should write to file from HOST
more details you may find in Ansys Fluent Customization manual
it contains pretty clear example chapter Writing Files in Parallel

best regards
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Old   May 15, 2019, 05:33
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..................

Last edited by pianaCFD; May 15, 2019 at 05:35. Reason: I set in the wrong place
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