[Yassin]

Can anyone help me in writing UDF for Di Felice drag model in DPM model?
Regards;

[AlexanderZ]

Ansys Fluent Customization manual -> DEFINE_DPM_DRAG macro

best regards

[Yassin]

I wrote Udf for Di Felice drag.
can you check it, please?
******************************
#include "udf.h"

#define pi 4.*atan(1.)

DEFINE_DPM_DRAG(dpm_DiFelice_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,
diam2, reyp1,void_g, void_s,Res, Cd, X, k_g_s;

cell_t cell;


/*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*/

diam2 =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*/
void_s = 1-void_g;/*particle vol frac*/

/*compute reynolds number*/
reyp =rho_g*abs_v*diam2 /mu_g; /*no volume fraction???*/
Res = void_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 = 1/8*Cd*void_g*rho_g*pi*diam2*diam2*abs_v*abs_v*pow(v of_g,-X);


return k_g_s;

}
****************

[AlexanderZ]

#include "udf.h"
#include "math.h"

#define pi 4.*atan(1.)

DEFINE_DPM_DRAG(dpm_DiFelice_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, 
diam2, reyp,void_g, void_s,Res, Cd, X, k_g_s;

cell_t cell;


/*find the cell index and thread of the cell that the particle is currently in*/
cell=P_CELL(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*/

diam2 =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*/
void_s = 1-void_g;/*particle vol frac*/

/*compute reynolds number*/
reyp =rho_g*abs_v*diam2 /mu_g; /*no volume fraction???*/ 
Res = void_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 = 1/8*Cd*void_g*rho_g*pi*diam2*diam2*abs_v*abs_v*pow(void_g,-X); 


return k_g_s;

}

I've checked only syntax, I don't know if you've apllied equations in right way or not.

check final equation in UDF

k_g_s = 1/8*Cd*void_g*rho_g*pi*diam2*diam2*abs_v*abs_v*pow(void_g,-X);

[Yassin]

Thanks for your replying.
I am facing the following problem when I interpreted the code:

: math.h: No such file or directory
:line 17: P_CELL: undeclared variable

[AlexanderZ]

compile this code

best regards