[walied123]

hello every body

i made a UDF for anode and cathode porosity in the SOFC module, but the energy residual get the following reading 1.#QNBe+00

PLEASE URGENT HELP.......
here is my UDF

#include "udf.h"

/**********************Anode Porosity **************/
DEFINE_PROFILE(anode_porosity, thread, np)
{
cell_t c;
real x[ND_ND];
real y;

begin_c_loop (c,thread)
{

C_CENTROID(x,c,thread);
y =x[1];

F_PROFILE(c,thread,np) =((y-1.53)/0.02)*(1-((y-1.53)/0.02));
}

end_c_loop (c,thread)

}

/*********************Cathode Porosity*****************/
DEFINE_PROFILE(cathode_porosity, thread, np)
{
cell_t c;
real x[ND_ND];
real y;

begin_c_loop (c,thread)
{

C_CENTROID(x,c,thread);
y=x[1];

F_PROFILE(c,thread,np) =((y-1.53)/0.02)*(1-((y-1.53)/0.02));
}

end_c_loop (c,thread)
}

[upeksa]

Take into account the following:

- Remember the units given by UDF are meters

- The values of porosity must be 0-1.

- You must set an appropriate value for Ri and Rv

[walied123]

thank you upeksa for your kind reply.
but what do you mean by Rv and Ri

regards

[upeksa]

Originally Posted by walied123

thank you upeksa for your kind reply.
but what do you mean by Rv and Ri

regards

Viscous resistence and inertial resistence.

Check this post

http://www.cfd-online.com/Forums/flu...us-medium.html

Looking at your UDF, nothing seems wrong with your code.

The error you get must have something to with some number out of range, so I think that the values of porosity you retrieve are higher than 1 or lower than 0.

Cheers

[walied123]

hello upeksa;

thank you for your kind reply.

please can you check the following udf for any error.i compiled it without any problems but i need to know is it right as a writing........ .

#include "udf.h"
#include "math.h"
/************************************************** CONSTANT****************************************** *************/
#define m 1
#define rua 1.2
#define thermal 0.0242
#define anode_density 4760
#define electrolyte_density 1980
#define anode_ca 377
#define ca 1006.43
#define electrolyte_ca 2000
#define anode_THER 11
#define electrolyte_THER 2
#define cathode_density 4640
#define cathode_ca 377
#define cathode_THER 2.37
/************************************************** Anode Porosity****************************************** ********************/
DEFINE_PROFILE(Anode_porosity, t, i)
{
cell_t c;
real x[ND_ND],y;

begin_c_loop(c,t)
{
C_CENTROID(x,c,t);
y=(x[1]*1000-1.56)/0.7;
C_PROFILE(c,t,i) = pow(y,m)*(1-pow(y,m));
}
end_c_loop (c,t)
}

/*************************************************C athode Porosity****************************************** ************************/
DEFINE_PROFILE(Cathode_porosity, t,i)
{

cell_t c;
real x[ND_ND],y;

begin_c_loop(c,t)
{
C_CENTROID(x,c,t);
y=(x[1]*1000-1.5)/0.05;
C_PROFILE(c,t,i) = pow(y,m)*(1-pow(y,m));
}

end_c_loop (c,t)
}

/*************************************************A node Density******************************************* *********************/
DEFINE_PROPERTY(A_Density, c,t)
{
real va, ve, p, d, u, y, x[ND_ND], dens, POR, po;
C_CENTROID(x,c,t);
y = x[1];
u = (y*1000 - 1.56) / 0.7;
va = pow(u, m); /* ve is the electrolyte material volume fraction*/
POR = C_POR(c,t);
ve = 1 - (va+POR); /* va is the anode material volume fraction*/
po = va*anode_density + ve*electrolyte_density;
dens = po*(1 - POR) + rua* POR;
return dens;
}
/*****************************************Anode thermal conductivity************************************** ***********/
DEFINE_PROPERTY(A_THER_cond,c,t)
{

real va, ve, p, d, u, x[ND_ND], POR, A, B, D, G, Lo,R,T,H, y, termal_cond_anode;
C_CENTROID(x,c,t);
y = x[1];
u = (y*1000 - 1.56) / 0.7;
va = pow(u, m);
POR = C_POR(c,t); /* va is the anode material volume fraction*/
ve = 1 - (va+POR); /* ve is the electrolyte material volume fraction*/
A = (3 * (anode_THER - electrolyte_THER)*va);
B = (3 * va*electrolyte_THER + (anode_THER +2* electrolyte_THER)*(1 - va));
Lo =electrolyte_THER*(1+( A / B));
D = Lo*(Lo*(1 - pow(POR, (2 / 3))) + thermal*pow(POR, (2 / 3)));
R = (pow(POR, (1 / 3))*thermal);
T = (1 - pow(POR, (1 / 3)))*((1 - pow(POR, 2 / 3))*Lo);
H = (1 - pow(POR, (1 / 3)))*(pow(POR, (2 / 3)))*thermal;
G = R + T + H;
termal_cond_anode = D / G;
return termal_cond_anode;
}
/********************************** CATHODE_DENSITY ************************************************** ******/
DEFINE_PROPERTY(C_Density, c,t)
{

real va, ve, p, d, u, y, x[ND_ND], dens, POR, po;

C_CENTROID(x,c,t);
y = x[1];
u = (y*1000 - 1.5) / 0.05;
POR = C_POR(c,t);
ve = pow(u, m); /* va is the anode material volume fraction*/
va = 1 - (ve+POR); /* ve is the electrolyte material volume fraction*/
po = va*anode_density + ve*electrolyte_density;
dens = po*(1 - POR) + rua* POR;
return dens;

}
/****************************************Cathode thermal conductivity************************************** ************/
DEFINE_PROPERTY(C_THER_cond, c,t)
{

real va, ve, p, d, u, x[ND_ND], POR, y,M,K,P,W, Lo,U1,J, termal_cond;
C_CENTROID(x,c,t);
y = x[1];
u = (y*1000 - 1.5) / 0.05;
POR = C_POR(c,t);
ve = pow(u, m); /* va is the anode material volume fraction*/
va = 1 - (ve+POR); /* ve is the electrolyte material volume fraction*/
M = (3 * (-cathode_THER + electrolyte_THER)*ve);
K = (3 * ve*cathode_THER + (2 * cathode_THER + electrolyte_THER)*(1 - ve));
Lo = cathode_THER*(1+(M / K));
P = Lo*(Lo*(1 - pow(POR, 2 / 3)) + thermal*pow(POR, 2 / 3));
J = pow(POR, 1 / 3)*thermal;
U1 = (1 - pow(POR, 1 / 3))*((1 - pow(POR, 2 / 3))*Lo);
W = (1 - pow(POR, 1 / 3))*(pow(POR, 2 / 3))*thermal;
termal_cond = P / (J + U1 + W);
return termal_cond;
}