how can i specify a parabolic distribution for inlet velocity for a 3-D elliptical jet with a major axis of 32mm and minor axis of 16mm. the maximum value of velocity is 165mm/sec. any help will be appreciated. thanks

For the above problem i am using the code FIDAP and i need help to apply the boundary conditions for inlet velocity using the module FIPREP....

you have to use a udf, which defines the profile.

CAN YOU TELL ME HOW TO USE AN UDF TO DEFINE THE PROFILE?

There are examples of udf available from your vendor.

They can tell you, how to use them. So far: if they are simple and there is no need to compile them, you just have to provide the udf-name and the path to your cc-compiler.

For examples have a look to the database for udf on cfd-online. Ask Jonas Larson (the moerator of cfd-online) where to find it.

Or try this:

/***********************************************/

/* Fully Developed laminar Inlet Condition */

/* for 2D-slit Problem with flow into y-direction */

/* velocity. Profile ref. to Blevins S41 Frame 1 Table 6.1*/

/* by V.Pawlik 18.04.2000 */

/***********************************************/

/*Remarks: printf except the warning, should be made to comments for final use, since the will be executed every iteration

ufree means u_central, the velocity on the centerline or at the end of the boundary layer !!! */

#include "udf.h"

/* coordinates of the inlet center */

/* maybe the following have to be changed

X[0]=x oder X[1]=y gegen X[2]=z */

#define xc 0.

#define yc 0.

/* here: radius means half slit with or distance from the symmetryline to the wall */

#define radius 0.0014

/*mean velocity: (Ufree=Ucenter!!) */

#define umean 0.232

/*================================================= =================*/

DEFINE_PROFILE(z_velocity, thread, position)

{

float r, x[2];

face_t f;

begin_f_loop(f, thread)

{

F_CENTROID(x,f,thread);

/* 3D: r = sqrt(pow(x[0]-xc, 2)+pow(x[1]-yc, 2)); */

/* here: r means not radius but distance from the centerline or symmetryline */ r = x[0]-xc;

F_PROFILE(f,thread,position)=2*umean*(1-pow(r/radius,2));

/* ************************************************** ***** */

/* controle output

printf("x=%.6f\t r=%.6f\t

u=%.5f\n",x[0],r,2*umean*(1-pow(r/radius,2))); */

/************************************************** *******/

}

end_f_loop(f, thread)

}

/*================================================= ===============*/