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 johnGo January 4, 2011 15:35

3D UDF Paraboilc Velocity Profile with max velocity

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"

{

real x[ND_ND];

real z; // Vertical Distance

face_t f;

{

z = x[2];

F_PROFILE(f, thread, position) = 24.9 *pow(z,0.27);

}

}

Thank you

 ComputerGuy January 4, 2011 22:45

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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