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UDF for Multiphase euilerian model

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Old   September 28, 2014, 05:40
Default UDF for Multiphase euilerian model
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Hi
I am conducting the two-phase eulerian model computaion.

In my model, the primary phase is CO2 gas and the secondary phase is dry-ice(CO2 solid).(I gave almost properties of dry-ice material manually)

I want to make the secondary phase(dry-ice) sublimate and change the primary phase(CO2 gas).
I heard that there is no sublimation model in fluent, so I coded udf for sublimation.

Inlet condition of the primary phase and the secondary phase is velocity inlet, 100m/s and temperature 220K. Outlet has 0Pa, gauge pressure, and 300K.
The model is calculated as a transient case and coupled solver is used.

The aim of my udf code is that if the cell temperature over some temperature criteria, then volume fraction of secondary phase would change 0 and reaction heat calculated by multiplying diappearing secondary phase mass and latent heat would be substracted from the entalphy of primary phase.

When I compiled and loaded my code, there is no problem.
However, when I ran the calculation, warning message('AMG solver divergence detected: pressure coupled' like this messages) is shown and calculation is interrupted.


My code is below,

#include "udf.h"

DEFINE_MASS_TRANSFER(sublimation, cell, thread, from_index, from_species_index, to_index, to_species_index)
{
Thread *dryice = THREAD_SUB_THREAD(thread, from_index);
Thread *gas = THREAD_SUB_THREAD(thread, to_index);


double Q_sub=575400;
double rho_d = C_R(cell,dryice);
double rho_g = C_R(cell,gas);
double vof_d = C_VOF(cell,dryice);
double vof_g = C_VOF(cell,gas);
double m_dot;
double T_gas=C_T(cell,gas);
double T_dryice=C_T(cell,dryice);
double T_sub=221;
m_dot=0.0;
if (T_dryice > T_sub)
{
C_VOF(cell,dryice) =0;
C_H(cell,gas) -= Q_sub*vof_d*rho_d/(vof_d*rho_d+vof_g*rho_g);

}
else if (T_dryice< T_sub)
{

}


}
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