[Musa]

I am modeling gas solid fluidized beds using different drag models. The Di Felice drag model I used compiles properly but it cannot predict fluidization in the bed. The bed does not fluidize. The code is given below. Any suggestions or advice?

#include "udf.h"

#define pi 4.*atan(1.)

DEFINE_EXCHANGE_PROPERTY(EMMS_Bubbling,cell,mix_th read,s_col,f_col)
{
Thread *thread_g, *thread_s;
real x_vel_g, x_vel_s, y_vel_g, y_vel_s, abs_v, slip_x, slip_y,
rho_g, rho_s, mu_g, reyp, Res,Cd,X,vof_g, vof_s,taup, k_g_s, diam2;

/* find the threads for the gas (primary) */
/* and solids (secondary phases) */

thread_g = THREAD_SUB_THREAD(mix_thread, s_col);/* gas phase */
thread_s = THREAD_SUB_THREAD(mix_thread, f_col);/* solid phase*/

/* find phase velocities and properties*/

x_vel_g = C_U(cell, thread_g);
y_vel_g = C_V(cell, thread_g);

x_vel_s = C_U(cell, thread_s);
y_vel_s = C_V(cell, thread_s);

slip_x = x_vel_g - x_vel_s;
slip_y = y_vel_g - y_vel_s;

rho_g = C_R(cell, thread_g);
rho_s = C_R(cell, thread_s);

mu_g = C_MU_L(cell, thread_g);

diam2 = C_PHASE_DIAMETER(cell, thread_s);

/*compute slip*/
abs_v = sqrt(slip_x*slip_x + slip_y*slip_y);

/*compute Reynold's number*/

reyp = rho_g*abs_v*diam2/mu_g;

/* compute particle relaxation time */

vof_g = C_VOF(cell, thread_g);/* gas vol frac*/
vof_s = C_VOF(cell, thread_s);/* particle vol frac*/

Res = vof_g * reyp;

Cd=pow((0.63+4.8*sqrt(1/Res),2);

X = 3.7-0.65*exp(-pow(1.5-log10(Res),2)/2);


/* Di Felice Model */
k_g_s = 3/4*Cd*vof_g*vof_s*rho_g*abs_v/diam2*pow(vof_g,-X);


return k_g_s;
}