UDF example

anni

Hello friends,

I believe that UDF manual is very badly written. I have succeded writting a UDF that is finally working and i want to share it with you, so people can have more examples , trying to write one...

A disk rotating and the angular velocity increments with time, till time reaches the 1.5 s. After 1.5 sec the rotation of the disk is 600rpm . In FLUENT I can only give UDF x,y velocity components and not rotational velocity. In my case the center of the axes is at the center of the disk.

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/*UDF for specifying a transient speed for disk */ #include "udf.h"

DEFINE_PROFILE(x_velocity, thread, position)

{

real x[ND_ND], y, u_vel, ron, rol, nn, nl, r;

real t = CURRENT_TIME;

face_t f;

r = 0.08; /* disk radious [m] */

nn = 400; /* [rpm] */

nl = 600; /* the final [rpm] */

ron = 2 * 3.14 * nn/60; /* rotational velocity [rad/s] */

rol = 2 * 3.24 * nl/60;

begin_f_loop(f, thread)

{

F_CENTROID(x,f,thread);

y = x[1];

if (t<=1.5)

{

u_vel = ron * r * t ; /* u=(w*r)*t */

F_PROFILE(f, thread, position) = u_vel * (-y)/r ; /* x-component of velocity */

}

else

{

u_vel = rol * r ; /* u=w*r */

F_PROFILE(f, thread, position) = u_vel * (-y)/r ; /* after 1.5 sec */

}

}

end_f_loop(f, thread)

}

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/*UDF for specifying a transient speed for disk */ #include "udf.h"

DEFINE_PROFILE(y_velocity, thread, position)

{

real x[ND_ND], xc, u_vel, ron, rol, nn, nl, r;

real t = CURRENT_TIME;

face_t f;

r = 0.08; /* disk radious [m] */

nn = 400; /* [rpm] */

nl = 600; /* rotation after the 1.5s [rpm] */

ron = 2 * 3.14 * nn/60; /* rotational velocity [rad/s] */

rol = 2 * 3.24 * nl/60;

begin_f_loop(f, thread)

{

F_CENTROID(x,f,thread);

xc = x[0];

if (t<=1.5)

{

u_vel = ron * r * t ; /* u=(w*r)*t */

F_PROFILE(f, thread, position) = u_vel * xc/r ; /* y component of velocity */

}

else

{

u_vel = rol * r ; /* u=w*r */

F_PROFILE(f, thread, position) = u_vel * xc/r ; /* time > 1.5 sec */

}

}

end_f_loop(f, thread)

}

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