UDF problem????

Mech

Hi I have coded the following UDF to adjust mass flow rate at the outlet. I have fixed pressure inlet and want to get given outlet pressure by adjusting massflow rate. When I use this UDF then the simulation does not converge. I am using pressure inlet at inlet boundary and mass flow inlet at outlet boundary.Can anybody correct it or give me suggestion. Thank in advance. Mech

#include <udf.h> #include <math.h> #define H 1.2e-06 #define L 0.003 #define W 0.00004 #define rhoin 2.92 #define cp 1038.45 #define therm 0.0242 #define Pin 272260.8 #define Pout 100800.00 #define Patm 100800.00

DEFINE_ADJUST(my_adjust, d) { Thread *t; cell_t c; real x[ND_ND]; double y, fst1, lst1, PR, z;

thread_loop_c (t,d) {

begin_c_loop (c,t)

{

C_CENTROID(x,c,t);

y=x[1];

y=sqrt(y*y);

z=x[0];

PR=Pin/Pout;

C_UDMI(c,t,1) = y;

C_UDMI(c,t,2) = (sqrt(gamma * R * temin));

}

end_c_loop (c,t) } }

DEFINE_PROFILE(mass_flow_inlet, t, i) {

real x3[ND_ND], x4[ND_ND]; real val, lamda, grad, Kn, du, dz, z1, z2, m3, dp, dx, p1; real pg1, m1;

face_t f;

cell_t c0;

Thread *t0;

m1=0.725; /*mass flux m1 assumed*/

pg1=5.70e+07; /*pressure gradient pg1*/

p1=100820.00 ; /*outlet pressure p1 */

begin_f_loop(f, t)

{

c0 = F_C0(f, t);

t0 = t -> t0;

dp=fabs(C_P(c0, t0)-F_P(f, t));

C_CENTROID(x3,c0,t0);

z1=x3[0];

F_CENTROID(x4,f,t);

z2=x4[0];

dz=fabs(z1-z2);

C_UDMI(c0,t0,4)= -(dp/dz); /* pressure gradient*/

C_UDMI(c0,t0,5)= C_R(c0,t0)*C_U(c0,t0)*H;

/* mass flow 2*rho*u*H */

if(F_P(f,t) != 100800.0)

{ m3=C_UDMI(c0,t0,5)-((Patm-F_P(f,t))/(p1-F_P(f,t)))*(C_UDMI(c0,t0,5)-m1);

m1=C_UDMI(c0,t0,5);

C_UDMI(c0,t0,5)=m3;

C_UDMI(c0,t0,6)=m1;

p1=F_P(f,t);

C_UDMI(c0,t0,7)=pg1;

}

F_PROFILE(f, t, i) = m3;

} end_f_loop(f, t) }

DEFINE_EXECUTE_AT_END(execute_at_end)

{

Thread *t; Domain *d;

real pg3, pg1, m1;

cell_t c; d=Get_Domain(1);

thread_loop_c (t,d)

{

begin_c_loop (c,t)

{

if((fabs(C_UDMI(c, t, 5)-C_UDMI(c,t,6))/H)> 1.5e-05)

{ C_P_G(c, t)[0]= -(C_UDMI(c, t, 4)- (C_UDMI(c, t, 5)/(C_UDMI(c, t, 5)-C_UDMI(c,t,6)))*(C_UDMI(c, t, 4)-C_UDMI(c, t, 7)));

C_UDMI(c, t, 7)= C_UDMI(c, t, 4); C_UDMI(c, t, 4)=C_P_G(c,t)[0];

}

}

end_c_loop (c,t)

} }