CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

Drag force correction

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   June 5, 2007, 05:24
Default Drag force correction
  #1
William
Guest
 
Posts: n/a
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
  Reply With Quote

Old   June 5, 2007, 09:07
Default Re: Drag force correction
  #2
bashu
Guest
 
Posts: n/a
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;

}
  Reply With Quote

Old   June 5, 2007, 10:11
Default Re: Drag force correction
  #3
Henrik
Guest
 
Posts: n/a
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
  Reply With Quote

Old   June 6, 2007, 00:09
Default Re: Drag force correction
  #4
William
Guest
 
Posts: n/a
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 !!!
  Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Force can not converge colopolo CFX 13 October 4, 2011 22:03
Force vectors for drag during sweeping motion aamer FLUENT 0 April 18, 2011 08:17
Drag force on scaled models. arunjingade Main CFD Forum 6 July 1, 2010 08:54
formula used for drag force? kamma Main CFD Forum 0 April 2, 2010 10:21
Actual drag force from dimensionless equations slaxmi CFX 10 September 14, 2007 19:20


All times are GMT -4. The time now is 10:02.