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-   -   Velocity boundary condtion UDF help (http://www.cfd-online.com/Forums/fluent-udf/107883-velocity-boundary-condtion-udf-help.html)

victoryv October 8, 2012 17:31

Velocity boundary condtion UDF help
 
I have a rectangular inlet (2x1-in X and Z)for a 3 D problem where I want to give a UDF for y velocity (-ve direction). The centre of the of the rectangular inlet is at (-2.5,2,8). The maximum velocity is 10. The profile is parabolic in x and z directon. I have written a UDF. But the velocity comes out to be >100.
I don't know where I'm I doing wrong.

/************************************************** ***********************/
/* udf- velocity profile boundary condition */
/************************************************** ***********************/

#include "udf.h"


DEFINE_PROFILE(inlet_y_velocity, thread, index)
{
real p[ND_ND];
real x,z;
face_t f;

begin_f_loop(f, thread)
{
F_CENTROID(p,f,thread);
x = p[1];
z= p[1];
F_PROFILE(f, thread, index) = (10-10*((x+2.5)*(x+2.5))-10*(((z-2)/0.5)*((z-2)/0.5)));
}
end_f_loop(f, thread)
}

flotus1 October 9, 2012 04:38

The x, y and z-values of the face centroids are stored in p[0], p[1] and p[2], respectively.

So first of all you should change the line "x=p[1];" to "x=p[0]"
and the line "z=p[1];" to "x=p[2]"

Didn't check the rest of your formula, so there could still be some more errors.

victoryv October 9, 2012 15:27

Thanks man.I totally forgot about that. I am getting proper results now. Also, I did miss negative sign in the formula.


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