Hello, I am working on a UDF for a problem with mass transfer at the interface between a liquid and a vapor layer. I use the DEFINE_MASS_TRANSFER macro to sweep, finding the interface by checking the volume of fluid using: (C_VOF(cell, liq) > 0.05) && (C_VOF(cell, liq) <= 0.95)) and then applying the mass transfer to just those cells that are at the interface. <\/p>\n
However, when I run this, I am not getting into the if-statement to check the VOF. My understanding is that the DEFINE macros will sweep and I do not need a loop to go through the faces (ie. begin_f_loop(f, thread), etc) but I’ve tried it with that as well with the same result. <\/p>\n
Also, I know that there is an interface because this is essentially a two-zone problem and I patch the zones at the beginning to have a liquid zone and a vapor zone. Plotting the VOF shows an area where the if statement is satisfied. Any ideas what I am missing here?<\/p>\n
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\/\/ UDF to define a simple mass transfer based on VOF.The “TO” phase is the gas and the “FROM” phase is the liquid phase<\/p>\n
#include “udf.h”
#include “sg_mphase.h”<\/p>\n
DEFINE_MASS_TRANSFER(liq_gas_source, cell, thread, from_index, from_species_index, to_index, to_species_index)
{
real m_lg;
real T_SAT = 373.15;
Thread* liq = THREAD_SUB_THREAD(thread, from_index);
Thread* gas = THREAD_SUB_THREAD(thread, to_index);
Message(“\\n \\n UDF IS DOING SOMETHING”);
m_lg = 0.;
face_t f;<\/p>\n
if ((C_VOF(cell, liq) > 0.05) && (C_VOF(cell, liq) <= 0.95))
{
Message(“\\n \\n I found the interface!”);
if (C_T(cell, liq) > T_SAT)
{ \/* Evaporating *\/
m_lg = -0.1 * C_VOF(cell, liq) * C_R(cell, liq) *
(C_T(cell, liq) – T_SAT) \/ T_SAT;
}
else if (C_T(cell, gas) < T_SAT)
{ \/* Condensing *\/
m_lg = 0.1 * C_VOF(cell, gas) * C_R(cell, gas) *
(T_SAT – C_T(cell, gas)) \/ T_SAT;
}<\/p>\n
}
return (m_lg);
}<\/p>\n
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