Hello !

Does anybody knows how can I use the Epstein drag force instead of Stokes-Cunningham on FLUENT? I'm trying to simulate a multiphase flow of a gas at low pressure with a low volume fraction of nanoparticles, in which the nanoparticle's size is much smaller than the mean free path of the gas molecules.

Thanks in advance

You can write something like this for your UDF and use it in the interaction panel for multiphase model. It seems you talking about dpm model. If so I don't have a sample for that. Hope this helps.

#include "udf.h"

#include "sg_mphase.h"

#define diam2 3.e-6

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, z_vel_g, z_vel_s,

rho_g, rho_s, mu_g, void_g, k_g_s, eps_s;

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

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

x_vel_g = C_U(cell, thread_g);

y_vel_g = C_V(cell, thread_g);

z_vel_g = C_W(cell, thread_g);

x_vel_s = C_U(cell, thread_s);

y_vel_s = C_V(cell, thread_s);

z_vel_s = C_W(cell, thread_s);

rho_g = C_R(cell, thread_g);

rho_s = C_R(cell, thread_s);

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

eps_s = C_VOF(cell, thread_s);/* solid vol frac*/

mu_g = C_MU_L(cell, thread_g);

k_g_s = .... ;

return k_g_s;

}

For the DPM model, write a UDF using the DEFINE_DPM_DRAG-macro. Example code is available in the manual. You then choose to use your UDF instead of Stokes-Cunningham in the drop-down menu in the DPM panel.

Good luck!

/Henrik

Thank you both for readily responses ! I will try something with UDF, though UDF seems tough work for a newbie like me. I will check the manual, and more suggestions are welcomed too.

Thanks everyone for your kind help !!!