[dinknflicka]

Hi all,

I am attempting to write a UDF to describe the decrease in a species mass fraction value and am needing a bit of guidance. The mass fraction will be described by first order kinetics, where I have experimentally determined a k constant. I understand that i basically need to use the DEFINE_SOURCE macro to create a 'sink'. I have written some code, but am getting an error that says not enough parameters for macro DEFINE_SOURCE. Here is my code so far...

#include "udf.h"

DEFINE_SOURCE(cell_death,c,t,i)
{
real source;
real k;
k=0.0000108840

source=-k*C_UDSI(c,t,0);

return source;
}

so I basically want to describe the rate of decrease is the species as
dN/dt= -0.0000108840 * (local concentration). I have a UDS set up with an inlet mass fraction and have the index set correctly, I'm just needing some guidance on what I'm missing to make this UDF work and describe the species mass fraction properly.

I would greatly appreciate any help that you all can offer.

Best

[AlexanderZ]

From ansys fluent customization manual
macro looks like

DEFINE_SOURCE (name, c, t, dS, eqn)

example

/*******************************************************************/
UDF for specifying an x-momentum source term in a spatially
dependent porous media
*******************************************************************/
#include "udf.h"
#define C2 100.0
DEFINE_SOURCE(xmom_source,c,t,dS,eqn)
{
real x[ND_ND];
real con, source;
C_CENTROID(x,c,t);
con = C2*0.5*C_R(c,t)*x[1];
source = -con*fabs(C_U(c, t))*C_U(c,t);
dS[eqn] = -2.*con*fabs(C_U(c,t));
return source;
}

best regards