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pradeep sivakumar June 7, 2001 14:59

PARABOLIC DISTRIBUTION OF VELOCITY
 
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

pradeep sivakumar June 7, 2001 20:26

Re: PARABOLIC DISTRIBUTION OF VELOCITY
 
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....

Volker Pawlik June 15, 2001 04:01

Re: PARABOLIC DISTRIBUTION OF VELOCITY
 
you have to use a udf, which defines the profile.

pradeep sivakumar June 15, 2001 11:03

Re: PARABOLIC DISTRIBUTION OF VELOCITY
 
CAN YOU TELL ME HOW TO USE AN UDF TO DEFINE THE PROFILE?

Volker Pawlik June 25, 2001 07:38

Re: PARABOLIC DISTRIBUTION OF VELOCITY
 
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)

}

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


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