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Old   August 25, 2009, 05:16
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hameurlaine
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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!
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Old   August 29, 2009, 04:43
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bgu
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Quote:
Originally Posted by louiza View Post
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); */

}
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Old   August 31, 2009, 05:52
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hameurlaine
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Thanks a lot !
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Old   February 4, 2010, 18:56
Default Yes, but the detail is not clear
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Michael McMaster
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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
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Old   March 10, 2010, 02:20
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Byron Smith R J
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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
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