[Michael.Z]

Hello all,

I want to set up a UDF mass source term that calculates a mass sink for every cell in my domain depending on the varying mass fraction of a certain species (water) in every cell.
The species should be reduced by a constant rate of 0.0002 per second. My domain is 2D axisymmetric and I run transient solver.

Here what I came up with so far:

DEFINE_SOURCE(sink,c,t,dS,eqn)
{
real sink;

if(C_YI(c,t,0)>0)
{

/* sink term definition: (mass fraction) x (density) x (sink constant rate) (kg/m3 s)*/
sink=-(C_YI(c,t,0)*(998.2)*(0.0002));

/* derivative of sink term */
dS[eqn] = 0;
}
else
sink = dS[eqn] = 0;

return sink;


The UDF is running perfectly fine showing reduction in the species in the domain but I am getting results that are off by some factors from what I expected.
I feel like I made a mistake setting up the sink term but I cant figure out what it is. I thought I might have to implement a loop over every cell but I'm not sure.

Thanks in advance for any help.

Michael