[kavatar]

Hello Everyone,

I am trying to store the normal distance of reconstructed interface from the cell center in each cell (if interface exists) in VOF Geo-reconstruct. I have come across the macro Get_Surface_Distance(c,t). The user defined function I am using is:

#include "udf.h"
#include "sg_mphase.h"
#include "sg_vof.h"
#include "sg.h"

DEFINE_ADJUST(gradient, domain)
{
#if !RP_HOST
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_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 *ppt = pt[phase_domain_index];

begin_c_loop (c,t)
{
//0.05 is my volume fraction cutoff criteria
if(C_VOF(c,ppt)>0.05 && C_VOF(c,ppt)<0.95)
{
C_UDMI(c,t,0)=Get_Surface_Distance(c,ppt);
}
else
{
C_UDMI(c,t,0)=0;
}
}
end_c_loop (c,t)
}
Free_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_NU LL);
#endif
}

This udf compiles without any error but when I run it on a grid It gives random values.

For example I take domain box (-5mm,-5mm,0) to (5mm,5mm,100mm). Subsequently mesh it into 10 equal cells with cell size of 10mm. Then I initialize multiphase (VOF) simulation as: from Z=0 to 30; Fraction_water=1, from Z=30 to 50; Fraction_water=0.75, and from Z=50 to 100; Fraction_Water=0.

After initialization I run the simulation for few time steps so that interface is reconstructed. Than I compile and hook the above udf and again re-run the simulation for single time step. After checking the UDMI_0 values I find that in cell where interface exists 0.05<C_VOF<0.95 or (30mm<Z<50mm); UDMI_0 values are 1.7977E+306 which is like garbage values.

Could anyone please help me solve this issue?. or If there is any other way to get the value of normal distance of interface from cell center than please let me know.

Thanks and Regards
Krishna

[AlexanderZ]

should it be brackets after mp_thread_loop_c (t,domain,pt)?

mp_thread_loop_c (t,domain,pt)
{}

also I'm not sure it the thread pointer should be t or ppt here

begin_c_loop (c,t)
{
//0.05 is my volume fraction cutoff criteria
if(C_VOF(c,ppt)>0.05 && C_VOF(c,ppt)<0.95)
{
C_UDMI(c,t,0)=Get_Surface_Distance(c,ppt);
}
else
{
C_UDMI(c,t,0)=0;
}
}
end_c_loop (c,t)

[kavatar]

Hello Alexander,

I have applied the brackets after mp_thread_loop_c (t,domain,pt) as per your suggestion.

My new udf look like:

#include "udf.h"
#include "sg_mphase.h"
#include "sg_vof.h"
#include "sg.h"

DEFINE_ADJUST(gradient, domain)
{
#if !RP_HOST
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_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 *ppt = pt[phase_domain_index];

begin_c_loop (c,t)
{
if(C_VOF(c,ppt)>0.05 && C_VOF(c,ppt)<0.95)
{
C_UDMI(c,t,0)=Get_Surface_Distance(c,ppt);
}
else
{
C_UDMI(c,t,0)=0;
}
}
end_c_loop (c,t)
}
}
Free_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_NU LL);
#endif
}


But the results value didn't change and I am still getting C_UDMI[0]=1.7977E+306 in interface cells.



Looking forward for your further suggestions


Also as per your second suggestion I took all the listed combinations of (ppt and t) as:

if(C_VOF(c,t)>0.05 && C_VOF(c,t)<0.95)
{
C_UDMI(c,t,0)=Get_Surface_Distance(c,t);
}

and

if(C_VOF(c,ppt)>0.05 && C_VOF(c,ppt)<0.95)
{
C_UDMI(c,t,0)=Get_Surface_Distance(c,t);
}

and

if(C_VOF(c,t)>0.05 && C_VOF(c,t)<0.95)
{
C_UDMI(c,t,0)=Get_Surface_Distance(c,ppt);
}

But none of these worked and I got the error as:

Error: received a fatal signal (Segmentation fault).
Error Object: #f

[kavatar]

Hello Alexander,

I guess the problem lies in the red colored line only:

#include "udf.h"
#include "sg_mphase.h"
#include "sg_vof.h"
#include "sg.h"

DEFINE_ADJUST(gradient, domain)
{
#if !RP_HOST
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_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 *ppt = pt[phase_domain_index];

begin_c_loop (c,t)
{
if(C_VOF(c,ppt)>0.05 && C_VOF(c,ppt)<0.95)
{
C_UDMI(c,t,0)=Get_Surface_Distance(c,ppt);
}
else
{
C_UDMI(c,t,0)=0;
}
}
end_c_loop (c,t)
}
}
Free_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_NU LL);
#endif
}

when I replace

C_UDMI(c,t,0)=Get_Surface_Distance(c,ppt);

with

C_UDMI(c,t,0)=C_VOF(c,ppt);

UDF works fine and volume fraction of water is stored in the UDMI.

Could you please check what is wrong with C_UDMI(c,t,0)=Get_Surface_Distance(c,ppt);.

I tried C_UDMI(c,t,0)=Get_Surface_Distance(c,t);, but this gives error as Error: received a fatal signal (Segmentation fault).
Error Object: #f

waiting for your response.

Thanks and regards
Krishna