# 3D UDF Paraboilc Velocity Profile with max velocity

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 January 4, 2011, 15:35 3D UDF Paraboilc Velocity Profile with max velocity #1 New Member   John Gosselin Join Date: Jan 2011 Location: quebec Posts: 3 Rep Power: 7 Hello, I am simulating the air flow over a 3D building in a wind domain using a paraboilc velocity inlet profile. I have this UDF but i would like have a max velocity in my UDF, exemple 5 m/s // UDF code for 3D parabolic Velocity Profile // #include "udf.h" DEFINE_PROFILE(inlet_x_velocity, thread, position) { real x[ND_ND]; real z; // Vertical Distance face_t f; begin_f_loop(f, thread) { F_CENTROID(x,f,thread); z = x[2]; F_PROFILE(f, thread, position) = 24.9 *pow(z,0.27); } end_f_loop(f, thread) } Thank you

 January 4, 2011, 22:45 #2 Senior Member   Real Name :) Join Date: Jan 2010 Location: United States Posts: 193 Rep Power: 8 If you just want to limit the velocity, you could look at the lesser of two values: your function, and 5.0. Like this: Code: ```#include "udf.h" DEFINE_PROFILE(inlet_x_velocity, thread, position) { real x[ND_ND]; real z; // Vertical Distance face_t f; begin_f_loop(f, thread) { F_CENTROID(x,f,thread); z = x[2]; F_PROFILE(f, thread, position) = MIN(24.9 *pow(z,0.27),5.0); } end_f_loop(f, thread) }``` If the MIN function is giving you trouble (can't remember if Fluent's interpreter has it built-in), you can get the same functionality with: Code: ```#include "udf.h" DEFINE_PROFILE(inlet_x_velocity, thread, position) { real x[ND_ND]; real z; // Vertical Distance face_t f; begin_f_loop(f, thread) { F_CENTROID(x,f,thread); z = x[2]; F_PROFILE(f, thread, position) = 24.9 *pow(z,0.27); if ((24.9 *pow(z,0.27))>5.) { F_PROFILE(f, thread, position) = 5.0; } } end_f_loop(f, thread) }```

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