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Old   October 18, 2013, 22:02
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Musango Lungu
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@Mohsen certainly the drag model has not been properly coded meaning the results obtained in the paper are questionable. Did the authors of the paper use the same code? If so bring it to their attention that the code has some errors! i.e. the definition of the particle reynolds number is not correct and the condition for switching to different regimes is missing.
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Old   October 19, 2013, 06:48
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I read thesis of the paper and in appendix of the thesis that code was written for gidaspow with switch function.and i think that the code has some errors.


thanks a lot for your replies Dear Musa ,You've helped me a lot.

I wish the best for you.
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Old   October 19, 2013, 07:09
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You are welcome buddy!
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Old   October 24, 2013, 15:18
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aoa, i have used this udf for gas solid fluidized bed and gives accurate results now i want to change from gas to liquid(water), tell me what are the changes required to do in code for this, waiting for ur reply
udf for customizing syamlal drag law in Fluent

#include "udf.h"
#define pi 4.*atan(1.)
#define diam2 3.e-4
DEFINE_EXCHANGE_PROPERTY(custom_drag, cell, mix_thread, 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, afac,
bfac, void_g, vfac, fdrgs, taup, k_g_s;
/* 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);
/*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 */
taup = rho_s*diam2*diam2/18./mu_g;
void_g = C_VOF(cell, thread_g);/* gas vol frac*/
/*compute drag and return drag coeff, k_g_s*/
afac = pow(void_g,4.14);
if(void_g<=0.85)
bfac = 0.281632*pow(void_g, 1.28);
else
bfac = pow(void_g, 9.076960);
vfac = 0.5*(afac-0.06*reyp+sqrt(0.0036*reyp*reyp+0.12*reyp*(2.*bfac-afac)+
afac*afac));
fdrgs = void_g*(pow((0.63*sqrt(reyp)/
vfac+4.8*sqrt(vfac)/vfac),2))/24.0;
k_g_s = (1.-void_g)*rho_s*fdrgs/taup;
return k_g_s;
}
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Old   October 24, 2013, 15:20
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i have used this udf for gas solid fluidized bed and gives accurate results now i want to change from gas to liquid(water), tell me what are the changes required to do in code for this, waiting for ur reply
udf for customizing syamlal drag law in Fluent

#include "udf.h"
#define pi 4.*atan(1.)
#define diam2 3.e-4
DEFINE_EXCHANGE_PROPERTY(custom_drag, cell, mix_thread, 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, afac,
bfac, void_g, vfac, fdrgs, taup, k_g_s;
/* 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);
/*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 */
taup = rho_s*diam2*diam2/18./mu_g;
void_g = C_VOF(cell, thread_g);/* gas vol frac*/
/*compute drag and return drag coeff, k_g_s*/
afac = pow(void_g,4.14);
if(void_g<=0.85)
bfac = 0.281632*pow(void_g, 1.28);
else
bfac = pow(void_g, 9.076960);
vfac = 0.5*(afac-0.06*reyp+sqrt(0.0036*reyp*reyp+0.12*reyp*(2.*bfac-afac)+
afac*afac));
fdrgs = void_g*(pow((0.63*sqrt(reyp)/
vfac+4.8*sqrt(vfac)/vfac),2))/24.0;
k_g_s = (1.-void_g)*rho_s*fdrgs/taup;
return k_g_s;
}
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Old   October 24, 2013, 20:48
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Musango Lungu
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@ Temour buddy sorry but I do not have any experience with gas-liquid fluidized beds!
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Old   July 19, 2016, 08:42
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adnan
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Quote:
Originally Posted by mohsen0488 View Post
Musa I tried with that code and the results were similar results of paper
so do you think results of this paper are incorrect?
How to write the UDF for DPM drag. I tried to write the UDF for DPM-Gidaspow drag model but it did not work properly. Any one can help me where I am wrong. Any help will be appreciated. Below is my UDF

#include "udf.h"
#include "dpm.h"
#define ZERO 0.0000001

DEFINE_DPM_DRAG(dpm_gidaspow_drag,Re,p)
{
Thread *thread_g, *thread_s, *mix_thread;
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, dp, reyp, reyp1,void_g, void_s, cd, D;
cell_t cell;
real left_term;
real dragcoefficient;

/*find the cell index and thread of the cell that the particle is currently in*/
cell=P_CELL_THREAD(p);
mix_thread=THREAD_SUB_THREAD(P_CELL_THREAD(p),0);

/* find the threads for the gas (primary) */

thread_g = THREAD_SUB_THREAD(mix_thread,0);/* gas phase thread */
thread_s = THREAD_SUB_THREAD(mix_thread,1);/* solid phase thread */
/* find phase velocities and properties*/

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

x_vel_s=P_VEL(p)[0];
y_vel_s=P_VEL(p)[1];

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

rho_g = C_R(cell, thread_g); /*density*/
rho_s =P_RHO(p);

mu_g = C_MU_L(cell, thread_g); /*laminar viscosity*/

dp =P_DIAM(p);

/*compute slip*/
abs_v = sqrt(slip_x*slip_x + slip_y*slip_y); /*absolute value of slip velocity*/

void_g = C_VOF(cell, thread_g);/* gas vol frac*/

Message ("Voidage of gas phase %f \n", void_g);

void_s = 1-void_g;/*particle vol frac*/

/*compute reynolds number*/
reyp =rho_g*abs_v*dp/mu_g; /*no volume fraction???*/
reyp1 = void_g*reyp;


if(reyp1<1000)
cd=24/reyp1*(1+0.15*pow(reyp1,0.687));
else
cd = 0.44;
if (void_g <=0.8)
{
/* Ergun Drag Model */
D = 150.0*void_s*void_s*mu_g/void_g/dp/dp+1.75*void_s*rho_g*abs_v/dp;
}
else
{
/* Wen & Yu Model */
D = 0.75*cd*void_g*void_s*rho_g*abs_v/dp/pow(void_g,2.65);
}

left_term=rho_s*pow(dp,2)/mu_g;
dragcoefficient=left_term*D/(abs_v+ZERO);
return dragcoefficient;

}
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