[lilistar-8216]

Hi, I'd like to get mass fraction data and store UDM at the end of tilmestep.
I tried calculation with UDF that can execute value at the end of tilmestep but it doesn't work and i get segmentation error.

My UDF is here,

#include "udf.h"
#include "sg_pdf.h"
#include "pdf_props.h"

DEFINE_EXECUTE_AT_END(mass_fraction)
{
Domain *d;
Thread *t;
cell_t c;
d = Get_Domain(1);
real mass;

thread_loop_c(t,d)
{
begin_c_loop(c, t)
{
mass = Pdf_Yi(c, t, 54); /*54 is an index of species i want to get value */
C_UDMI(c, t, 0) = mass;
Message("mf = %g\n", mass);
}
end_c_loop(c,t)
}
}

my calculation model has both solid zone and fluid zone. Addition to that, I use an Chemkin as a species model.

I also tried to change Pdf_Yi(cat,54) into C_YI(c,t,54) but it also didn't work.

Do you know if there are some problems in my UDF or not, how to use C_YI or Pdf_Yi macros, or the other ways to get mass fraction value at the end of tilmestep without these macros.

regards

[Likitha]

In most of the cases while we use UDM we need to allocate the memory first.
It can be done it 2 ways :
1. by setting the parameters /solve/set/expert in the fluent TUI.
2. Or by allocating the variables using Alloc_Storage_Vars(domain, SV_*_RG, SV_*_G, SV_NULL) macro. In most of the cases the 2nd method is advisable while using UDF.

So try allocating memory and let me know if you still face the problem.

[AlexanderZ]

when did you get segmentation error,
if on initialization:
user-defined -> memory -> udm locations 1

best regards

[mahdi-united]

Originally Posted by Likitha

In most of the cases while we use UDM we need to allocate the memory first.
It can be done it 2 ways :
1. by setting the parameters /solve/set/expert in the fluent TUI.
2. Or by allocating the variables using Alloc_Storage_Vars(domain, SV_*_RG, SV_*_G, SV_NULL) macro. In most of the cases the 2nd method is advisable while using UDF.

So try allocating memory and let me know if you still face the problem.

hi

what is the argument should be put in * in SV_*_G for mass fraction?

[vinerm]

It is Y and since there are multiple components, an additional argument is required; so it written as

SV_Y_G, 0

for first component

[mahdi-united]

Originally Posted by vinerm

It is Y and since there are multiple components, an additional argument is required; so it written as

SV_Y_G, 0

for first component

thanks for responding
and what is your reference ?
i want to know more information about arguments of SV_*_G

[vinerm]

Look at the source listing in your installation

./ansys_inc/vXXX/fluent/fluentXX.Y.Z/src

[mahdi-united]

Originally Posted by vinerm

Look at the source listing in your installation

./ansys_inc/vXXX/fluent/fluentXX.Y.Z/src

where??


i not found this address in my computer

[vinerm]

Location varies from computer to computer. You have to find where Ansys products are installed in your computer. I have given the path further from there. If it is Windows, then most likely in Program Files. If it is Linux then it could be anywhere. Just type command

which fluent

in the terminal and it will show the location.

[mahdi-united]

Originally Posted by vinerm

Location varies from computer to computer. You have to find where Ansys products are installed in your computer. I have given the path further from there. If it is Windows, then most likely in Program Files. If it is Linux then it could be anywhere. Just type command

which fluent

in the terminal and it will show the location.

yes i found it
thank you so much

[mahdi-united]

Originally Posted by vinerm

Location varies from computer to computer. You have to find where Ansys products are installed in your computer. I have given the path further from there. If it is Windows, then most likely in Program Files. If it is Linux then it could be anywhere. Just type command

which fluent

in the terminal and it will show the location.

dear friend



this is my code to storing volume fraction and mass fraction gradient in DEFINE_ADJUST
is it right??
thanks a lot


DEFINE_ADJUST(gradient, domain)
{
Thread *t;
Thread **pt;
cell_t c;
Domain *pDomain = DOMAIN_SUB_DOMAIN(domain,P_PHASE);
real voidx, voidy, voidz=0.0;
{
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);
}
{
Alloc_Storage_Vars(domain, SV_Y_RG,0, SV_Y_G,0, SV_NULL);
//Yi_derivatives(domain);
Free_Storage_Vars(domain, SV_Y_RG,0, SV_NULL);
}
mp_thread_loop_c (t,domain,pt)
if (FLUID_THREAD_P(t))
{
Thread *tp = pt[P_PHASE];
begin_c_loop (c,t)
{
// (C_VOF_G(c,tp)[0]*C_T_G(c,t)[0]+C_VOF_G(c,tp)[1]*C_T_G(c,t)[1]+C_VOF_G(c,tp)[2]*C_T_G(c,t)[2]);
C_UDMI(c,t,0) = C_YI_G(c,tp,0)[0];//(C_VOF_G(c,tp)[0]*C_YI_G(c,tp,0)[0] + C_VOF_G(c,tp)[1]*C_YI_G(c,tp,0)[1] + C_VOF_G(c,tp)[2]*C_YI_G(c,tp,0)[2]);
}
end_c_loop (c,t)
}
Free_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_NU LL);
Free_Storage_Vars(domain, SV_Y_G,0, SV_NULL);
//Message("C_UDMI(cell,mix_air,0) = %g\n",C_UDMI(c,t,0));
}


i dont know is the YI_derivatives right or mistake

[vinerm]

Allocation and reconstruction is available on domain. So, use

Alloc...(domain

instead of

Alloc...(pDomain

Do not use braces unnecessarily; will make code ambiguous. Use Free command only if Alloc has been used.

[mahdi-united]

Originally Posted by vinerm

Allocation and reconstruction is available on domain. So, use

Alloc...(domain

instead of

Alloc...(pDomain

Do not use braces unnecessarily; will make code ambiguous. Use Free command only if Alloc has been used.

thanks. i will solve it but

IS the Yi_derivatives right??
is there any problem in code?

[vinerm]

Well, those ones appear to be alright to me. You can confirm by plotting their contours. To be able to do that, you have to issue the following command and then run at least 1 iteration

solve set expert

and then select yes to the question about Keeping Memory from being freed.

[vinerm]

Do you mean the literal Yi_derivatives command? There is no such command in Fluent.

[mahdi-united]

Originally Posted by vinerm

Well, those ones appear to be alright to me. You can confirm by plotting their contours. To be able to do that, you have to issue the following command and then run at least 1 iteration

solve set expert

and then select yes to the question about Keeping Memory from being freed.

all of this you say done

but code can't access to mass fraction gradient and will appear error in iteration1.

[mahdi-united]

Originally Posted by vinerm

Do you mean the literal Yi_derivatives command? There is no such command in Fluent.

exactly my problem is Yi_derivatives

but in source files that you told me i not found anything about Yi_derivatives

[vinerm]

Post the modified code. Do note that Fluent does not accept // as argument. Change those to /* */.

[mahdi-united]

Originally Posted by vinerm

Post the modified code. Do note that Fluent does not accept // as argument. Change those to /* */.

hi dear friend
T_derivatives function in is not in sources files in ANSYS_INC
do you confident?

[vinerm]

T_derivatives function is declared in pbns/sg.h, however, I do not think that it is relevant for you. You need to fetch gradients of mass fractions of species. That is accessible via C_YI_G or as stated earlier, using SV_Y_G, 0.

What error do you get if you use either C_YI_G or SV_Y_G? I would recommend the former since that is an easy wrapper for users.