It's really strange, I have compiled the udf and the compiler tells me this :

udf_final_velocity_check.c: In function ‘some_func’: udf_final_velocity_check.c:6: warning: excess elements in array initializer udf_final_velocity_check.c:6: warning: (near initialization for ‘r0’) udf_final_velocity_check.c:7: warning: excess elements in array initializer udf_final_velocity_check.c:7: warning: (near initialization for ‘v0’) udf_final_velocity_check.c:5: warning: unused variable ‘vel’ udf_final_velocity_check.c: In function ‘inlet_axial_velocity’: udf_final_velocity_check.c:23: warning: unused variable ‘v’ # Linking libudf.so because of makefile user.udf udf_names.c udf_names.o udf_final_velocity_check.o ld -shared -lm udf_names.o udf_final_velocity_check.o -o libudf.so make[3]: warning: Clock skew detected. Your build may be incomplete. make[3]: Leaving directory `/home/cdiakodi/Desktop/Fluent_fran_fran/maillage_pr_fluent/new_2/lnamd64/3d' make[2]: warning: Clock skew detected. Your build may be incomplete. make[2]: Leaving directory `/home/cdiakodi/Desktop/Fluent_fran_fran/maillage_pr_fluent/new_2/lnamd64/3d' make[1]: warning: Clock skew detected. Your build may be incomplete. make[1]: Leaving directory `/home/cdiakodi/Desktop/Fluent_fran_fran/maillage_pr_fluent/new_2/lnamd64/3d'

an idea ?

It happens if you the array initializer has more elements than the array declared
In the above example "r0" is an integer array of length three while the initializer has four elements. In my post I wrote it as
There should be no warning.

You were right, the UDF works now.

Thank you!

Just one last question: how can I change the UDF that we have created to add a velocity profile of particles (using DPM)?