[combustion]

Hi,

Fluent 14 has a macro for looking up mole and mass fractions of species for non-premixed combustion cases:

Pdf_XY(cell c, thread *t, x, y)

I am trying to write a source term for a UDS to duplicate the Brookes and Moss two equation soot model that is already built into fluent. I will later modify my source terms to make a new 2-eqn model.

My problem is that when I don't know how the species are indexed in fluent. Is the indexing based on the flamelet library or based on the pdf-mixture species list?

I have attached my code for one of the source terms.

Thanks for your help.

#include "udf.h"
#include "pdf_props.h"
#include "pdf_table.h"
#include "mem.h"
#include "materials.h"

/*********Constant Declarations*************************************/
#define c_alph 54.0 /* Units: 1/s */
#define N_avog 6.022045e+26 /* 1/kmol */
#define c_bet 1.0 /* no units */
#define rho_soot 1800.0 /* kg/m3 */
#define T_alph 21000.0 /* activation temperature of soot inception in K */
#define N_norm 1.0e+15 /* Moss-Brookes model: normalizing parameter */
#define l 1.0 /* l indicates the particle nucleation sensitivity to Pressure: defined as 1.0 for now */
#define PI 3.14159265358979324 /* Pi as a constant...alternatively pi=4.0*atan(1.0) */
#define SpNo 20 /* The number of species in the mechanism file: should be adjusted according to the mechanism */
#define Species 22 /* This is the index for the species of interest (C2H2 in this case) */
/*********End Constant Declarations*********************************/

DEFINE_SOURCE(n_sourceterm, c, ct, dS, eqn)
{
/*********Variable Declarations*************************************/
double dNdT, dp, X_C2H2, T, P, rho_cell, M, N, Ysoot, bNuc, R;
double x[SpNo], y[SpNo]; /* x is the array for species mole fractions and y is the array for mass fractions */
int id_c2h2;
/*********End Variable Declarations*********************************/

/*********Variable Assignments**************************************/
Material *mat = THREAD_MATERIAL(ct);
id_c2h2 = mixture_specie_index(mat, "c2h2");
Pdf_XY(c, ct, x, y); /* Calling the species mole and mass fractions for this cell */
X_C2H2 = x[id_c2h2]; /* arbitrarily defined for now */
T = C_T(c, ct); /* Temperature at the cell */
if (c == 400)
Message("Temp is %g\n, species %", T);
P = C_P(c, ct); /* Cell Presdsure */
if (c == 400)
Message("Press is %g\n, ", P);
rho_cell = C_R(c, ct); /* Cell average Density */
R = UNIVERSAL_GAS_CONSTANT; /* Universal gas constant is called with the built-in Fluent Macro */

Ysoot = C_UDSI(c, ct, 0); /* Calling soot mass fraction from m_sourceterm scalar */
if (c == 400)
Message("Ysoot is %g\n, ", Ysoot);

bNuc = C_UDSI(c, ct, 1); /* Calling soot number density from n_sourceterm scalar */
if (c == 400)
Message("bNuc is %g\n, ", bNuc);
/**********End Variable Assignments*********************************/

/**********Start Calculations************************************** */
M = rho_cell * Ysoot;
N = bNuc * rho_cell * N_norm;
dp = pow(((6.0 * M)/(PI * N * rho_soot)), (1.0/3.0));
dNdT = c_alph * N_avog * pow(((X_C2H2 * P)/(R * T)), l) * exp(-1.0 * T_alph / T) - c_bet * pow(((24.0 * R * T) / ( rho_soot * N_avog)), 0.5) * sqrt(dp) * pow(N, 2);
if (c == 400)
Message("dNdT is %g\n, ", dNdT);
/**********End of Calculations**************************************/

return (dNdT / N_norm);

}

[pghoseju]

I desperately want to edit the constants of moss brooks soot model. But till now I did not get any idea. Is it possible to do such by any way? If possible please tell me.

[combustion]

Hi Prakash,
The answer is No and Yes.
No: you cannot modify the constants in the Fluent solver. There is no option to go that route.

Yes: you can write a UDF for a two-eqn model and manipulate the coefficients as you see fit.

[pghoseju]

Thank you sir for your kind response.

Yes I want to create duplicate source term equations. In my result I am having c2h2. Any way I want to know how can I call temperature, pressure and specially mass fraction of C2H2 (Xprec, Xsgs) by udf. Also I want to know how can I call cell density for calculation of M and N.

Can you plz help me?

[pghoseju]

Sir Kaveh,
The same problem I am too facing. I am also using steady flamelet model. I got C2H2 in flamelet mixture. I also want to know what is the value of 'i' (index) so that I can use C_YI (c,t,i). I have number of species under pdf mixture and below it again number of species under flamelet mixture. So how can I count for species index? Should I start for pdf mixture or what???

plz help me

[combustion]

Hi Prakash,

Who is "Sir" Kaveh?
I found out that you can find the species index by putting the following segment in your code:

/***************************************/
Material *mat = THREAD_MATERIAL(ct); /* This segment determines the species index number */
id_c2h2 = mixture_specie_index(mat, "c2h2");
/**************************************/

The example above is for acetylene. You can find any species index in the same manner. So, id_c2h2 is the variable that contains the species index for c2h2 which is an integer.

I hope this was useful.

[pghoseju]

Thank you for your kind response.

[pghoseju]

Sir,
When I am interpreting it, it shows the following error.

Error: C:/Users/AMITAD~1/AppData/Local/Temp/udf soot 1_2.c.1.c: line 63: function "mixture_specie_index" not found (pc=87).
Error: C:/Users/AMITAD~1/AppData/Local/Temp/udf soot 1_2.c.1.c: line 63: function "Pdf_XY" not found (pc=101).
Error: C:/Users/AMITAD~1/AppData/Local/Temp/udf soot 1_2.c.1.c: line 63: function "CX_Message" not found (pc=150).
Error: C:/Users/AMITAD~1/AppData/Local/Temp/udf soot 1_2.c.1.c: line 63: function "CX_Message" not found (pc=186).
Error: C:/Users/AMITAD~1/AppData/Local/Temp/udf soot 1_2.c.1.c: line 63: function "CX_Message" not found (pc=246).
Error: C:/Users/AMITAD~1/AppData/Local/Temp/udf soot 1_2.c.1.c: line 63: function "CX_Message" not found (pc=282).
Error: C:/Users/AMITAD~1/AppData/Local/Temp/udf soot 1_2.c.1.c: line 63: function "CX_Message" not found (pc=405).

[combustion]

Have you included the proper libraries?

#include "materials.h"
#include "pdf_table.h"

[pghoseju]

Sir,
I included following libraries.

#include "udf.h"
#include "pdf_props.h"
#include "pdf_table.h"
#include "mem.h"
#include "materials.h"

[combustion]

can you post your code here?

[pghoseju]

Sorry sir for late response. I was out of my city for few days. Actually I am using the UDF written by you on this forum. Again I was doing a great mistake that, I was interpreting the UDF in ANSYS 13.0 but now previous error is not there because now I am using Ansys 14.0.

But some new error came.
cpp -I"C:\PROGRA~1\ANSYS Inc\v140\fluent\fluent14.0.0/src" -I"C:\PROGRA~1\ANSYS Inc\v140\fluent\fluent14.0.0/cortex/src" -I"C:\PROGRA~1\ANSYS Inc\v140\fluent\fluent14.0.0/client/src" -I"C:\PROGRA~1\ANSYS Inc\v140\fluent\fluent14.0.0/multiport/src" -I. -
UDFCONFIG_H="<C:/Users/WINDOW~1/AppData/Local/Temp/udfconfig-node0.h>" "C:/Users/WINDOW~1/AppData/Local/Temp/udf soot 1_2.c.0.c"
Error: C:\\PROGRA~1\\ANSYS Inc\\v140\\fluent\\fluent14.0.0/src/pdf_table.h: line 141: ran off top of typedef queue (300).

cpp -I"C:\PROGRA~1\ANSYS Inc\v140\fluent\fluent14.0.0/src" -I"C:\PROGRA~1\ANSYS Inc\v140\fluent\fluent14.0.0/cortex/src" -I"C:\PROGRA~1\ANSYS Inc\v140\fluent\fluent14.0.0/client/src" -I"C:\PROGRA~1\ANSYS Inc\v140\fluent\fluent14.0.0/multiport/src" -I. -
UDFCONFIG_H="<C:/Users/WINDOW~1/AppData/Local/Temp/udfconfig-node1.h>" "C:/Users/WINDOW~1/AppData/Local/Temp/udf soot 1_2.c.1.c"
Error: C:\\PROGRA~1\\ANSYS Inc\\v140\\fluent\\fluent14.0.0/src/pdf_table.h: line 141: ran off top of typedef queue (300).

[pghoseju]

The red marks I cannot get anythging from udf HELP
I found in udf help it is written like Bold letter I have written. Sir plz can you help me regarding this metter

#include "udf.h"
#include "pdf_props.h"
#include "pdf_table.h"
#include "mem.h"
#include "materials.h"

/*********Constant Declarations*************************************/
#define c_alph 54.0 /* Units: 1/s */
#define N_avog 6.022045e+26 /* 1/kmol */
#define c_bet 1.0 /* no units */
#define rho_soot 1800.0 /* kg/m3 */
#define T_alph 21000.0 /* activation temperature of soot inception in K */
#define N_norm 1.0e+15 /* Moss-Brookes model: normalizing parameter */
#define l 1.0 /* l indicates the particle nucleation sensitivity to Pressure: defined as 1.0 for now */
#define PI 3.14159265358979324 /* Pi as a constant...alternatively pi=4.0*atan(1.0) */
#define SpNo 20 /* The number of species in the mechanism file: should be adjusted according to the mechanism */
#define Species 22 /* This is the index for the species of interest (C2H2 in this case) */
/*********End Constant Declarations*********************************/

DEFINE_SOURCE(n_sourceterm, c, ct, dS, eqn)
{
/*********Variable Declarations*************************************/
double dNdT, dp, X_C2H2, T, P, rho_cell, M, N, Ysoot, bNuc, R;
double x[SpNo], y[SpNo]; /* x is the array for species mole fractions and y is the array for mass fractions */
int id_c2h2; ic2h2
/*********End Variable Declarations*********************************/

/*********Variable Assignments**************************************/
Material *mat = THREAD_MATERIAL(ct); Material *m = THREAD_MATERIAL(t);
id_c2h2 = mixture_specie_index(mat, "c2h2"); ic2h2 = mixture_specie_index(m, "c2h2");
Pdf_XY(c, ct, x, y); Pdf_XY(c, t, x, y);/* Calling the species mole and mass fractions for this cell */
X_C2H2 = x[id_c2h2]; X_C2H2 = xi[ic2h2]; /* arbitrarily defined for now */
T = C_T(c, ct); T = C_T(c, t)/* Temperature at the cell */
if (c == 400)
Message("Temp is %g\n, species %", T);
P = C_P(c, ct); P = C_P(c, t)/* Cell Presdsure */
if (c == 400)
Message("Press is %g\n, ", P);
rho_cell = C_R(c, ct); rho_cell = C_R(c, t);/* Cell average Density */
R = UNIVERSAL_GAS_CONSTANT; /* Universal gas constant is called with the built-in Fluent Macro */

Ysoot = C_UDSI(c, ct, 0); Ysoot = C_UDSI(c, t, 0);/* Calling soot mass fraction from m_sourceterm scalar */
if (c == 400)
Message("Ysoot is %g\n, ", Ysoot);

bNuc = C_UDSI(c, ct, 1); bNuc = C_UDSI(c, t, 1);/* Calling soot number density from n_sourceterm scalar */
if (c == 400)
Message("bNuc is %g\n, ", bNuc);
/**********End Variable Assignments*********************************/

/**********Start Calculations************************************** */
M = rho_cell * Ysoot;
N = bNuc * rho_cell * N_norm;
dp = pow(((6.0 * M)/(PI * N * rho_soot)), (1.0/3.0));
dNdT = c_alph * N_avog * pow(((X_C2H2 * P)/(R * T)), l) * exp(-1.0 * T_alph / T) - c_bet * pow(((24.0 * R * T) / ( rho_soot * N_avog)), 0.5) * sqrt(dp) * pow(N, 2);
if (c == 400)
Message("dNdT is %g\n, ", dNdT);
/**********End of Calculations**************************************/

return (dNdT / N_norm);

}

[pghoseju]

Sir I am posting my full udf, which is not running.
Plz help me.




#include "udf.h"
#include "pdf_props.h"
#include "pdf_table.h"
#include "mem.h"
#include "materials.h"

/*********Constant Declarations*************************************/
#define c_alph 54.0 /* Units: 1/s */
#define N_avog 6.022045e+26 /* 1/kmol */
#define c_bet 1.0 /* no units */
#define rho_soot 1800.0 /* kg/m3 */
#define T_alph 21000.0 /* activation temperature of soot inception in K */
#define N_norm 1.0e+15 /* Moss-Brookes model: normalizing parameter */
#define l 1.0 /* l indicates the particle nucleation sensitivity to Pressure: defined as 1.0 for now */
#define PI 3.14159265358979324 /* Pi as a constant...alternatively pi=4.0*atan(1.0) */
#define SpNo 20 /* The number of species in the mechanism file: should be adjusted according to the mechanism */
#define Species 22 /* This is the index for the species of interest (C2H2 in this case) */

#define Mp 144.0 /* mass of an incipent soot particle. here taken for C12 */
#define c_gama 11700.0 /* surface growth rate scaling factor */
#define T_gama 12100.0 /* activation temperature of surface growth rate */
#define m 1.0
#define n 1.0
#define c_oxid 0.015
#define c_omega 105.8125
#define eta_coll 0.04
/*********End Constant Declarations*********************************/

DEFINE_SOURCE(n_sourceterm, c, ct, dS, eqn)
{
/*********Variable Declarations*************************************/
double dNdT, dp, X_C2H2, X_OH, T, P, rho_cell, M, N, Ysoot, bNuc, R;
double x[SpNo], y[SpNo]; /* x is the array for species mole fractions and y is the array for mass fractions */
int id_c2h2;
int id_oh
/*********End Variable Declarations*********************************/

/*********Variable Assignments**************************************/
Material *mat = THREAD_MATERIAL(ct);
id_c2h2 = mixture_specie_index(mat, "c2h2");
id_oh = mixture_species_index(mat, "oh");
Pdf_XY(c, ct, x, y); /* Calling the species mole and mass fractions for this cell */
X_C2H2 = x[id_c2h2]; /* arbitrarily defined for now */
X_OH = x[id_oh];

T = C_T(c, ct); /* Temperature at the cell */
if (c == 400)
Message("Temp is %g\n, species %", T);

P = C_P(c, ct); /* Cell Presdsure */
if (c == 400)
Message("Press is %g\n, ", P);

rho_cell = C_R(c, ct); /* Cell average Density */

R = UNIVERSAL_GAS_CONSTANT; /* Universal gas constant is called with the built-in Fluent Macro */

Ysoot = C_UDSI(c, ct, 0); /* Calling soot mass fraction from m_sourceterm scalar */
if (c == 400)
Message("Ysoot is %g\n, ", Ysoot);

bNuc = C_UDSI(c, ct, 1); /* Calling soot number density from n_sourceterm scalar */
if (c == 400)
Message("bNuc is %g\n, ", bNuc);
/**********End Variable Assignments*********************************/

/**********Start Calculations************************************** */
M = rho_cell * Ysoot;
N = bNuc * rho_cell * N_norm;

dp = pow(((6.0 * M)/(PI * N * rho_soot)), (1.0/3.0));

dNdT = c_alph * N_avog * pow(((X_C2H2 * P)/(R * T)), l) * exp(-1.0 * T_alph / T) - c_bet * pow(((24.0 * R * T) / ( rho_soot * N_avog)), 0.5) * sqrt(dp) * pow(N, 2);
if (c == 400)

dMdT = Mp * C_alph * pow(((X_C2H2 * P)/(R * T)), l) * exp(-1.0 * T_alph / T) + c_gama * pow(((X_C2H2 * P)/(R * T)), m) * (exp(-1.0 * T_gama / T) * (pow((pi * N), 1.0/3.0)) * (pow((6 * M)/rho_soot), 2.0/3.0)) - c_oxid * c_omega * eta_coll

* ((X_OH * P) / (R * T)) * sqrt(T) * pow((pi * N), 1.0/3.0) * pow((6*M/rho_soot), 2.0/3.0)

Message("dNdT is %g\n, ", dNdT);
/**********End of Calculations**************************************/

return (dNdT / N_norm);
return (dMdT);

}

[pghoseju]

Dear kaveh.
I am giving my uds source code for soot mass fraction. Another code for nuclei is also there but I am not giving that, because both are similar.
But still error is showing. can you plz help me.

#include "udf.h"
#include "pdf_props.h"
#include "pdf_table.h"
#include "mem.h"
#include "materials.h"
#include "sg_udms.h"

/*********Constant Declarations*************************************/

#define Mp 144.0 /* mass of an incipent soot particle. here taken for C12 */
#define c_alph 54.0 /* Units: 1/s */
#define T_alph 21000.0 /* activation temperature of soot inception in K */
#define c_gama 11700.0 /* surface growth rate scaling factor */
#define T_gama 12100.0 /* activation temperature of surface growth rate */
#define c_oxid 0.015 /* oxidation rate scaling parameter */
#define c_omega 105.8125 /* oxidation model constant */
#define eta_coll 0.04 /* collisional efficiency parameter */
#define rho_soot 1800.0 /* kg/m3 */
#define l 1.0 /* indicates the particle nucleation sensitivity to Pressure */
#define m 1.0 /* indicates the particle surface growth sensitivity to Pressure */
#define n 1.0 /* indicates the particle surface growth sensitivity to soot mass concentration */
#define PI 3.14159265358979324 /* Pi as a constant...alternatively pi=4.0*atan(1.0) */


/*********End Constant Declarations*********************************/

DEFINE_SOURCE(m_sourceterm, c, t, dS, eqn)
{
/*********Variable Declarations*************************************/
double dMdT, X_C2H2, X_OH, T, P, rho_cell, M, N, Ysoot, bNuc, R;

int ic2h2;
int ioh;
/*********End Variable Declarations*********************************/

/*********Variable Assignments**************************************/
Material *m = THREAD_MATERIAL(t);
ic2h2 = mixture_specie_index(m, "c2h2");
ioh = mixture_species_index(m, "oh");

Pdf_XY(c, t, x, y); /* Calling the species mole and mass fractions for this cell */
X_C2H2 = xi[ic2h2];
X_OH = xi[ioh];

T = C_T(c, t); /* Temperature at the cell */
if (c == 400)
Message("Temp is %g\n, species %", T);

P = C_P(c, t); /* Cell Pressure */
if (c == 400)
Message("Press is %g\n, ", P);

rho_cell = C_R(c, t); /* Cell average Density */

R = UNIVERSAL_GAS_CONSTANT; /* Universal gas constant is called with the built-in Fluent Macro */

Ysoot = C_UDSI(c, t, 0); /* Calling soot mass fraction from m_sourceterm scalar */
if (c == 400)
Message("Ysoot is %g\n, ", Ysoot);

bNuc = C_UDSI(c, t, 1); /* Calling soot number density from n_sourceterm scalar */
if (c == 400)
Message("bNuc is %g\n, ", bNuc);
/**********End Variable Assignments*********************************/

/**********Start Calculations************************************** */
M = rho_cell * Ysoot;
N = bNuc * rho_cell * N_norm;

dMdT = Mp * C_alph * pow(((X_C2H2 * P)/(R * T)), l) * exp(-1.0 * T_alph / T) + c_gama * pow(((X_C2H2 * P)/(R * T)), m) * (exp(-1.0 * T_gama / T) * (pow((pi * N), 1.0/3.0)) * (pow((6 * M)/rho_soot), 2.0/3.0)) - c_oxid * c_omega * eta_coll * ((X_OH * P) / (R * T)) * sqrt(T) * pow((pi * N), 1.0/3.0) * pow((6*M/rho_soot), 2.0/3.0)

Message("dMdT is %g\n, ", dMdT);
/**********End of Calculations**************************************/

return (dMdT);

}

[doni]

hi pghoseju
i cant undrestand what is UDSI , im new in udf , i have to define udf for UDSI? can u help me?

[hbilal1076]

following.........

[duanwuCHEN]

Now, it is 2023, I'm still looking for a way to do so. Even though there are macros to rewrite the soot nuclei rate and the soot mass rate, I compiled and selected them successfully in Fluent, while there show no significant between with or without macro.

[fabiu50]

Originally Posted by pghoseju

I desperately want to edit the constants of moss brooks soot model. But till now I did not get any idea. Is it possible to do such by any way? If possible please tell me.

If someone wants to do this just access the Fluent soot model via terminal
define/models/soot-model/soot-model-parameters
and then you can change all constants of the Moss-Brookes model.