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Di Felice drag model FLUENT UDF

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Old   September 11, 2013, 01:51
Default Di Felice drag model FLUENT UDF
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Musango Lungu
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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;
}
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Old   November 25, 2013, 04:20
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Prashant Gupta
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Hi Musa,

Did you find the minimum fluidization velocity using De Felice ?
I suggest take up a case from literature, with a known minimum fluidization velocity. and compare with the solution you are getting.

Alternatively, you could simple test set ups like single particle sedimentation, and block of constant particles falling to check against analytical solutions.

I am also testing these, with EDEM-Fluent.

Kind regards
Prashant
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