[Laexzzz]

Please answer a few questions about UDS.

My case: UDS move with material flow, and source term of scalar depend of concentarion of material specie concentration.

Questions:

0. If i set "mass flow rate" in flux function of UDS, scalar "speed" = speed of material flow?

1. In boundary condition of inlet i set:
Scalar bound condition - Flux
Scalar Boundary value = 1.
But in after calculation, contours of scalar = 680. Why?

2. I set source term of scalar. Code:

#include "udf.h"
#define kd0 1.58e+15

DEFINE_SOURCE(UDS_source,c,t,dS,eqn)
{

real UDS_source;
real temp = C_T(c,t);
real Dens = C_R(c,t);
real kd = kd0*exp(-15500/temp);

UDS_source = -kd*C_UDSI(c,t,0);
dS[eqn] = 0;
return Ini_source;
}

(or dS[eqn] = -kd, result is the same)

So, by equation -kd*C_UDSI(c,t,0) rate of scalar "conversion" = -2 * 10^-06 each second. But scalar doesnt change or change very little.

3. When i choose different type of initializing, the results are different. Why?

4. I want to set the source of scalar = sink of 1 material specie. My code:

DEFINE_SOURCE(UDS0_source,c,t,dS,eqn)
{

real UDS0_source;
real temp = C_T(c,t);
real Dens = C_R(c,t);
real kd = kd0*exp(-15500/temp);
real ComponentA_MolarConc;
real SinkOfComponentA;

ComponentA_MolarConc = (C_YI(c,t,0)*Dens) / 164;
SinkOfComponentA = -kd*ComponentA_MolarConc
UDS0_source = -SinkOfComponentA;
dS[eqn] = 0.0;

return UDS0_source;
}

Units
kd = [1/s]
ComponentA_MolarConc = [kmol/m^3]

So, source of UDS0 = [kmol/m^3*s]?

But after calculation, ComponentA_MolarConc varies from 0.015 to 0.09, and UDS0 varies from 0.016 to 0.054 (!). Any ideas?