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Old   May 25, 2006, 04:29
Default evaporation in vof
  #1
asghari
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Hi all, how to involve evaporation process in vof by udf's? can everybody give me an example(with respective udf) in this case? thank all.

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Old   May 25, 2006, 21:11
Default Re: evaporation in vof
  #2
cg
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Here's a UDF to propagate the VOF interface at a specified speed. I think that you can modify this accordingly for evaporation...

#include "udf.h" #include "sg.h" #include "sg_mphase.h" #include "flow.h" #include "mem.h"

/************************************************** ************/ /* UDF for specifying an interfacial area density */ /************************************************** ************/

#define flame_speed 2.;

DEFINE_ADJUST(area_density, domain) { Thread *t; Thread **pt; cell_t c; Domain *pDomain = DOMAIN_SUB_DOMAIN(domain,P_PHASE); real voidx, voidy, voidz=0;

Alloc_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_N ULL); Scalar_Reconstruction(pDomain, SV_VOF,-1,SV_VOF_RG,NULL); Scalar_Derivatives(pDomain,SV_VOF,-1,SV_VOF_G,SV_VOF_RG,Vof_Deriv_Accumulate);

mp_thread_loop_c (t,domain,pt)

if (FLUID_THREAD_P(t))

{

Thread *tp = pt[P_PHASE];

begin_c_loop (c,t)

{

voidx = C_VOF_G(c,tp)[0];

voidy = C_VOF_G(c,tp)[1]; #if RP_3D

voidz = C_VOF_G(c,tp)[2]; #endif

/* calculation of the interfacial area density */

C_UDMI(c,t,0)= sqrt( SQR(voidx) + SQR(voidy) + SQR(voidz) );

}

end_c_loop (c,t)

}

Free_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_NU LL); }

DEFINE_SOURCE(reactants, cell, thread, dS, eqn) { real source; Thread *tm = THREAD_SUPER_THREAD(thread); Thread **pt = THREAD_SUB_THREADS(tm); source = - C_UDMI(cell, tm, 0)*C_R(cell,pt[0]); source *= flame_speed; dS[eqn] = 0; return source; }

DEFINE_SOURCE(product, cell, thread, dS, eqn) { real source; Thread *tm = THREAD_SUPER_THREAD(thread); Thread **pt = THREAD_SUB_THREADS(tm); source = C_UDMI(cell, tm, 0)*C_R(cell,pt[0]); source *= flame_speed; dS[eqn] = 0; return source; }

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Old   May 26, 2006, 11:03
Default Re: evaporation in vof
  #3
greg
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meby this will help you. By the way do you know haw to add a :from_species_index and to_species_index? the is only from_phase_index and to_phase_index. I don`t know how to do it.

/* UDF to define a simple mass transfer based on Saturation

Temperature. The "from" phase is the gas and the "to" phase is the

liquid phase */

#include "udf.h"

DEFINE_MASS_TRANSFER(liq_gas_source,cell,thread,fr om_index,from_species_index, to_index, to_species_index) {

real m_lg;

real T_SAT = 373.15;

Thread *gas = THREAD_SUB_THREAD(thread, from_index);

Thread *liq = THREAD_SUB_THREAD(thread, to_index);

m_lg = 0.;

if (C_T(cell, liq) >= T_SAT)

{

m_lg = -0.1*C_VOF(cell,liq)*C_R(cell,liq)*

fabs(C_T(cell,liq)-T_SAT)/T_SAT;

}

if ((m_lg == 0. ) && (C_T(cell, gas) <= T_SAT))

{

m_lg = 0.1*C_VOF(cell,gas)*C_R(cell,gas)*

fabs(T_SAT-C_T(cell,gas))/T_SAT;

}

return (m_lg); }
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Old   May 27, 2006, 02:58
Default Re: evaporation in vof
  #4
asghari
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thank you , But is this UDF included heat transfer process and may be included this process?
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