CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT > Fluent UDF and Scheme Programming

Direct condensation of steam to subcooled water spray

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree1Likes
  • 1 Post By pakk

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   November 18, 2021, 10:57
Exclamation Direct condensation of steam to subcooled water spray
  #1
New Member
 
mohammad reza
Join Date: Apr 2014
Location: Iran-Isfahan
Posts: 10
Rep Power: 11
m.r.soufivand is on a distinguished road
As in the article " https://doi.org/10.1016/j.cep.2019.04.015 ", I want to simulate direct condensation of steam to subcooled water spray.

The results are good when I simulate only hydrodynamics, but when I compile the UDF to mass transfer and add source terms, In the first few iterations, it diverges and gives the following error:
"WARNING: Invalid cp (0.000000e+00 J/kgK) for water-vapor at temperature nan K
Error at host: floating point exception
Error: floating point exception
Error Object: #f"



I have attached the UDF to this post. I would be grateful if you could help me.
Attached Files
File Type: txt UDF.txt (2.8 KB, 6 views)

Last edited by m.r.soufivand; November 18, 2021 at 11:00. Reason: I forgot to upload the attachment
m.r.soufivand is offline   Reply With Quote

Old   November 19, 2021, 00:18
Default
  #2
Senior Member
 
Alexander
Join Date: Apr 2013
Posts: 2,363
Rep Power: 34
AlexanderZ will become famous soon enoughAlexanderZ will become famous soon enough
your code
Code:
#include "udf.h"
#include "math.h"
#include "sg.h"
#include "sg_mphase.h"
#include "flow.h"
#include "mem.h"
#include "metric.h"
#define R 8.314
#define pi 3.14159
#define T_SAT 373.15
#define h_lv 2455.1345e3
#define M 18.0
#define Beta 0.6666
#define a 23.224
#define b 3841.22
#define cc  -45.0

DEFINE_ADJUST(store_gradient, domain)
{
Thread *t;
Thread **pt;
cell_t c;
int phase_domain_index = 0.;
Domain *pDomain = DOMAIN_SUB_DOMAIN(domain,phase_domain_index);
Alloc_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_NULL);
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 *ppt = pt[phase_domain_index];

begin_c_loop (c,t)
{
C_UDMI(c,t,0) = C_VOF_G(c,ppt)[0];
C_UDMI(c,t,1) = C_VOF_G(c,ppt)[1];
C_UDMI(c,t,2) = NV_MAG(C_VOF_G(c,ppt));

}
end_c_loop (c,t)
}
Free_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_NULL);
}
DEFINE_SOURCE(vap_src, cell, pri_th, dS, eqn)
{
Thread *mix_th, *sec_th;
real m_dot_v,T_v,T_l,P_v,P_sat;
mix_th = THREAD_SUPER_THREAD(pri_th);
sec_th = THREAD_SUB_THREAD(mix_th,1);
T_v=C_T(cell,pri_th);
P_v=C_P(cell,pri_th);
T_l=C_T(cell,sec_th);
P_sat=exp(a-(b/(T_l+cc)));
if(C_T(cell,mix_th)>=T_SAT)
{
m_dot_v = 0.0;

dS[eqn] = 0.0;
}

if(C_T(cell,mix_th)<=T_SAT)
{
m_dot_v =C_VOF(cell,sec_th)*(2.0*Beta/(2.0-Beta))*C_UDMI(cell,mix_th,2)*sqrt(M/(2*pi*R))*((P_v/sqrt(T_v))-(P_sat/sqrt(T_l)));
C_UDMI(cell,mix_th,3) =m_dot_v;
dS[eqn] = 0.0;
}
return m_dot_v ;
}
DEFINE_SOURCE(liq_src,cell,sec_th,dS,eqn)
{
Thread * mix_th, *pri_th;
real m_dot_l,T_v,T_l,P_v,P_sat;
mix_th=THREAD_SUPER_THREAD(sec_th);
pri_th=THREAD_SUB_THREAD(mix_th,0);
T_v = C_T(cell,pri_th);
P_v = C_P(cell,pri_th);
T_l = C_T(cell,sec_th);
P_sat=exp(a-(b/(T_l+cc)));
if(C_T(cell,mix_th)>=T_SAT)
{
m_dot_l = 0.0;
dS[eqn] = 0.0;
}
if(C_T(cell,mix_th)<=T_SAT)
{
m_dot_l = C_VOF(cell,sec_th)*(2.0*Beta/(2.0-Beta))*C_UDMI(cell,mix_th,2)*sqrt(M/(2*pi*R))*((P_v/sqrt(T_v))-(P_sat/sqrt(T_l)));
C_UDMI(cell,mix_th,4) =m_dot_l;
dS[eqn] =(2.0*Beta/(2.0-Beta))*C_UDMI(cell,mix_th,2)*sqrt(M/(2*pi*R))*((P_v/sqrt(T_v))-(P_sat/sqrt(T_l)));
}

return m_dot_l;
}
DEFINE_SOURCE(enrg_src,cell,mix_th,dS,eqn)
{
Thread *pri_th, *sec_th;
real m_dot,T_v,T_l,P_v,P_sat;
pri_th = THREAD_SUB_THREAD(mix_th,0);
sec_th = THREAD_SUB_THREAD(mix_th,1);
T_v=C_T(cell,pri_th);
P_v=C_P(cell,pri_th);
T_l=C_T(cell,sec_th);
P_sat=exp(a-(b/(T_l+cc)));
if(C_T(cell,mix_th)>=T_SAT)
{
m_dot =0.0;
dS[eqn] =0.0;
}

if(C_T(cell,mix_th)<=T_SAT)
{
m_dot=C_VOF(cell,sec_th)*(2.0*Beta/(2.0-Beta))*C_UDMI(cell,mix_th,2)*sqrt(M/(2*pi*R))*((P_v/sqrt(T_v))-(P_sat/sqrt(T_l)));
C_UDMI(cell,mix_th,5) =h_lv*m_dot;
dS[eqn]= 0.0;

}
return h_lv*m_dot; }
in this code I would change only 1 thing, which probably will not affect
was #define h_lv 2455.1345e3
to be #define h_lv 2.4551345e6

from your error I may assume you have problem with temperature convergence.
you may decrease time step
check your mesh
check boundary conditions
__________________
best regards


******************************
press LIKE if this message was helpful
AlexanderZ is offline   Reply With Quote

Old   November 19, 2021, 05:58
Default
  #3
Senior Member
 
Join Date: Nov 2013
Posts: 1,965
Rep Power: 26
pakk will become famous soon enough
I tried to refactor your code, because you repeated your equations a few times:

Code:
#include "udf.h"
#include "math.h"
#include "sg.h"
#include "sg_mphase.h"
#include "flow.h"
#include "mem.h"
#include "metric.h"
#define R 8.314
#define pi 3.14159
#define T_SAT 373.15
#define h_lv 2455.1345e3
#define M 18.0
#define Beta 0.6666
#define a 23.224
#define b 3841.22
#define cc  -45.0

DEFINE_ADJUST(store_gradient, domain)
{
 Thread *t;
 Thread **pt;
 cell_t c;
 int phase_domain_index = 0.;
 Domain *pDomain = DOMAIN_SUB_DOMAIN(domain,phase_domain_index);
 Alloc_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_NULL);
 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 *ppt = pt[phase_domain_index];
  begin_c_loop (c,t)
  {
   C_UDMI(c,t,0) = C_VOF_G(c,ppt)[0];
   C_UDMI(c,t,1) = C_VOF_G(c,ppt)[1];
   C_UDMI(c,t,2) = NV_MAG(C_VOF_G(c,ppt));
  }
 end_c_loop (c,t)
 }
Free_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_NULL);
}

real ds(Thread* pri_th, Thread* sec_th, cell_t cell) {
 real T_v, T_l, P_v, P_sat, dS;
 if(C_T(cell,mix_th)>=T_SAT) {
  dS = 0;
 } else {
  T_v=C_T(cell,pri_th);
  P_v=C_P(cell,pri_th);
  T_l=C_T(cell,sec_th);
  P_sat=exp(a-(b/(T_l+cc)));dS;
  dS = (2.0*Beta/(2.0-Beta))*C_UDMI(cell,mix_th,2)*sqrt(M/(2*pi*R))*((P_v/sqrt(T_v))-(P_sat/sqrt(T_l)));
 }
 return dS;
}

real mdot(Thread* pri_th, Thread* sec_th, cell_t cell) {
 real T_v, T_l, P_v, P_sat, m_dot;
 if(C_T(cell,mix_th)>=T_SAT) {
  m_dot = 0;
 } else {
  T_v=C_T(cell,pri_th);
  P_v=C_P(cell,pri_th);
  T_l=C_T(cell,sec_th);
  P_sat=exp(a-(b/(T_l+cc)));
  m_dot = C_VOF(cell,sec_th)*(2.0*Beta/(2.0-Beta))*C_UDMI(cell,mix_th,2)*sqrt(M/(2*pi*R))*((P_v/sqrt(T_v))-(P_sat/sqrt(T_l)));
 }
 return m_dot;
}

DEFINE_SOURCE(vap_src, cell, pri_th, dS, eqn)
{
 Thread* mix_th = THREAD_SUPER_THREAD(pri_th);
 Thread* sec_th = THREAD_SUB_THREAD(mix_th,1);
 real m_dot_v=mdot(pri_th, sec_th, cell);
 C_UDMI(cell,mix_th,3) = m_dot_v;
 dS[eqn] = 0.0;
 return m_dot_v ;
}

DEFINE_SOURCE(liq_src,cell,sec_th,dS,eqn)
{
 Thread* mix_th=THREAD_SUPER_THREAD(sec_th);
 Thread* pri_th=THREAD_SUB_THREAD(mix_th,0);
 real m_dot_l=mdot(pri_th, sec_th, cell);
 C_UDMI(cell,mix_th,4) = m_dot_l;
 dS[eqn] = ds(pri_th, sec_th, cell);
 return m_dot_l;
}

DEFINE_SOURCE(enrg_src,cell,mix_th,dS,eqn)
{
 Thread* pri_th = THREAD_SUB_THREAD(mix_th,0);
 Thread* sec_th = THREAD_SUB_THREAD(mix_th,1);
 real m_dot=mdot(pri_th, sec_th, cell);
 C_UDMI(cell,mix_th,5) = h_lv*m_dot;
 dS[eqn]= 0.0;
 return h_lv*m_dot; 
}
This should be functionally the same (but I did not test it). What is now more apparent is that your two mass sources have the same sign, where I would expect them to differ in sign (whatever leaves the liquid zone should enter the vapor zone and vice versa).

I also noticed that only one of your sources specifies dS (as non-zero); the code above is (relatively) easy to change if you want to improve that.
m.r.soufivand likes this.
__________________
"The UDF library you are trying to load (libudf) is not compiled for parallel use on the current platform" is NOT the error after compiling. It is the error after loading. To see compiler errors, look at your screen after you click "build".
pakk is offline   Reply With Quote

Old   November 19, 2021, 09:15
Default
  #4
New Member
 
mohammad reza
Join Date: Apr 2014
Location: Iran-Isfahan
Posts: 10
Rep Power: 11
m.r.soufivand is on a distinguished road
Thanks so much for your response and help. I try to use your code but gives the error is that mix_th is not defined.
m.r.soufivand is offline   Reply With Quote

Old   November 20, 2021, 02:47
Default
  #5
Senior Member
 
Join Date: Nov 2013
Posts: 1,965
Rep Power: 26
pakk will become famous soon enough
I see, the definitions for ds and mdot should also have this:

Code:
Thread* mix_th = THREAD_SUPER_THREAD(pri_th);
__________________
"The UDF library you are trying to load (libudf) is not compiled for parallel use on the current platform" is NOT the error after compiling. It is the error after loading. To see compiler errors, look at your screen after you click "build".
pakk is offline   Reply With Quote

Reply

Tags
condensation, divergence issue, mass transfer, udf

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Mass imbalance problem in multiphase water and steam CFX case Antech CFX 1 October 26, 2020 04:03
VOF Steam condensation Andrea159357 FLUENT 4 March 19, 2019 14:20
No liquid water exist in my Fuel Cell simulation fatchang FLUENT 19 October 15, 2018 14:27
Steam Mixture material for Wall condensation coolcrasher CFX 2 October 19, 2015 09:23
How to solve condensation case with HBM model (NO WATER)? kiwishall CFX 0 December 23, 2013 20:47


All times are GMT -4. The time now is 12:42.