# UDF species equations

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

 August 25, 2009, 05:16 UDF species equations #1 New Member   hameurlaine Join Date: Jul 2009 Posts: 27 Rep Power: 9 Hello all, I would like to modeling arc discharge in argon (ideal gaz) with 6 reactions and 3 species, for this I need to solving the transport equation with source term via UDF that includes (construction species , destruction species) . I wrote the source term = the ensemble of creation and destruction of species in an analytical form, I get a set of equations (N) with N incconu. [dAr/dt]=k3*[ne]*[Ar]+k4*[ne]*[Ar*]+......... [dAr*/dt]=k2*[ne]*[Ar]-k4*[ne]*[Ar*]-......... [dAr/dt], [dAr*/dt]: molar concentration of atom of argon, and excited atom of argon. k2, k3 : rate reaction2 and 3 depend of electronc temperature. k4 : rate reaction (4) is constant. The reaction rates depending on the electron temperature and there are some constant. How do I solve this set of equations and if you have any UDF examples for species equations please let me send. please help me Thank you!

August 29, 2009, 04:43
#2
New Member

Join Date: Mar 2009
Posts: 9
Rep Power: 9
Quote:
 Originally Posted by louiza Hello all, I would like to modeling arc discharge in argon (ideal gaz) with 6 reactions and 3 species, for this I need to solving the transport equation with source term via UDF that includes (construction species , destruction species) . I wrote the source term = the ensemble of creation and destruction of species in an analytical form, I get a set of equations (N) with N incconu. [dAr/dt]=k3*[ne]*[Ar]+k4*[ne]*[Ar*]+......... [dAr*/dt]=k2*[ne]*[Ar]-k4*[ne]*[Ar*]-......... [dAr/dt], [dAr*/dt]: molar concentration of atom of argon, and excited atom of argon. k2, k3 : rate reaction2 and 3 depend of electronc temperature. k4 : rate reaction (4) is constant. The reaction rates depending on the electron temperature and there are some constant. How do I solve this set of equations and if you have any UDF examples for species equations please let me send. please help me Thank you!
Please look at the FLUENT 6.3 UDF manual chapter 2.3.22
If it not available to you, I copied the relevant example which deals with
two reactions.
Instead of the lines /*Reaction xx*/ put your own reactions and replace the
reaction names in the example with your names in the Reactions panel.
Finally, after compilation, make it available in the UDF hooks panel under
Volumetric Reaction Rate,

/************************************************** *******************
Multiple reaction UDF that specifies different reaction rates
for different volumetric chemical reactions
************************************************** ********************/
#include "udf.h"

DEFINE_VR_RATE(myrate,c,t,r,mw,yi,rr,rr_t)
{
/*If more than one reaction is defined, it is necessary to distinguish
between these using the names of the reactions. */

if (!strcmp(r->name, "reaction-1"))
{
/* Reaction 1 */
}
else if (!strcmp(r->name, "reaction-2"))
{
/* Reaction 2 */
}
else
{
/* Message("Unknown Reaction\n"); */
}
/* Message("Actual Reaction: %s\n",r->name); */

}

 August 31, 2009, 05:52 #3 New Member   hameurlaine Join Date: Jul 2009 Posts: 27 Rep Power: 9 Thanks a lot !

 February 4, 2010, 18:56 Yes, but the detail is not clear #4 New Member   Michael McMaster Join Date: May 2009 Posts: 29 Rep Power: 9 hi BGU and louisa, i am doing similar, catalytic reactions in packed beds, which require non power law rate equations to be written. I had figured out that i need to write a UDF for this before looking at this thread, but if i have say three components involved in the reaction how do i specify these in the rate equation in the UDF, is it based on the species mass fraction index, yi, from the header: DEFINE_VR_RATE( name,c,t,r,mw,yi,rr,rr_t) So essentially the first is y1, the second is y2 and the third is y3? I suppsoe i should try this before asking, but couldnt help myself. Any guidance will be greatly appeciated. Michael

 March 10, 2010, 02:20 #5 Member   Byron Smith R J Join Date: Mar 2009 Location: India Posts: 46 Rep Power: 9 hai the order of Yi comes from the order of listing the components and it starts with 0 and not 1. get the massfractions and then convert them into required terms to use in hte rate of reaction equation

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post biget.a FLUENT 2 July 23, 2009 03:06 MRR FLUENT 0 December 29, 2005 08:14 Fernando FLUENT 0 September 3, 2004 08:22 Ale FLUENT 0 July 18, 2003 09:04 Jamiro FLUENT 0 June 20, 2001 17:15

All times are GMT -4. The time now is 12:18.