Hi How can I write a UDF of the boundary condition T(t)=Tm+Asin(wt), where T is the temperature, t=time, Tm=mean temaperature, A= amplitude=DeltaT/2, w=2pi/P=angular freequency, P=24 for the fluent....

ITs very easy just check some examples in udf document. P

Hi P, Thanks for your advice. I wrote the following but could not getting the result.

#include "udf.h" DEFINE_PROFILE(Surface_hotflux_profile,t,i) { real x[ND_ND]; /* this will hold the position vector */ /* real xS; y direction */ /* real tempS; surface temperature*/

/* real Bi=1.; Biot number*/ real deltaTime=86400.; /* recycling time of day and night*/

real timeB=RP_Get_Real("flow-time"); real vt; face_t f;

if ( timeB<deltaTime) /*1 recycling*/

{

vt=timeB;

} if ( timeB>=deltaTime) /*2 recycling*/

{

vt=timeB-deltaTime;

}

if ( timeB>=deltaTime*2.) /*3 recycling*/

{

vt=vt-deltaTime;

}

if ( timeB>=deltaTime*3.) /*4 recycling*/

{

vt=vt-deltaTime;

}

if ( timeB>=deltaTime*4.) /*5 recycling*/

{

vt=vt-deltaTime;

}

if ( timeB>=deltaTime*5.) /*6 recycling*/

{

vt=vt-deltaTime;

}

if ( timeB>=deltaTime*6.) /*7 recycling*/

{

vt=vt-deltaTime;

}

if ( timeB>=deltaTime*7.) /*8 recycling*/

{

vt=vt-deltaTime;

}

if ( timeB>=deltaTime*8.) /*9 recycling*/

{

vt=vt-deltaTime;

}

if ( timeB>=deltaTime*9.) /*10 recycling*/

{

vt=vt-deltaTime;

}

if ( timeB>=deltaTime*10.) /*11 recycling*/

{

vt=vt-deltaTime;

}

if ( vt>deltaTime/2.)

{

begin_f_loop(f,t)

{

/* tempS=F_T(f,t); get temp in surface */

F_CENTROID(x,f,t);

F_PROFILE(f, t, i)=290.+5.*sin(2*3.141592654*vt/deltaTime);

}

end_f_loop(f,t)

}

else

{

begin_f_loop(f,t)

{

F_CENTROID(x,f,t);

F_PROFILE(f, t, i)=0.;

}

end_f_loop(f,t)

} }

Do you get some error message then cut and paste them here in order for us to help u. P

That's because you have not define sin function in the library. You need to write include math.h as well afer the include udf.h. This will define the sin function. Only UDF library is noy enough to recognise it.

Hope this help.

Sham.