[hbilal1076]

Dear Concern,

In Ansys Fluent, when I compile and load the UDF file, and also in the Cell zone conditions>Fluid I added/enabled the source term and uploaded the UDF file and even initialize but when I click on calculate, after 5 second it become terminated and get closed and back to the main page (main page I means where all tab of geometry, mesh, setup, solution are listed).

I even tried the other UDF sample model from fluent manual and it also get terminated.

Kindly explain the possible mistake that I am doing.

Thank you very much for your time and assistance.

Sincerely,

Bilal

[AlexanderZ]

show UDF code
show console output after you've loaded UDF.

[hbilal1076]

Dear Prof. AlexanderZ,
Thank you very much for your reply.
Here is my UDF file.

#include "udf.h"
DEFINE_SOURCE(energy,c,t,ds,eqn)
{
/*FILE *fp;*/
real source,tep,sigma,Pamb,tamb;
real MW[14];
real XH2O,Xco,XCO2,pH2O,pco,pCO2;
real MWmix,sum=0;
real kapa,absH2O,absco,absCO2;
real a0,a1,a2,a3,a4,a5;
real b0,b1,b2,b3,b4,b5;
real c0,c1,C2,c3,c4;
real d0,d1,d2,d3,d4;
int i;
/*fp=fopen("properties.txt","a+");*/
tep=C_T(c,t);
MW[0]=2;
MW[1]=1;
MW[2]=40;
MW[3]=44;
MW[4]=4;
MW[5]=16;
MW[6]=17;
MW[7]=29;
MW[8]=33;
MW[9]=18;
MW[10]=28;
MW[11]=32;
MW[12]=34;
MW[13]=28;
sigma=0.000000056697;
Pamb=1.0;
tamb=298.0;
a0=18.741;
a1=-121.310;
a2=273.500;
a3=-194.05;
a4=56.31;
a5=-5.8169;
b0=-0.23093;
b1=1.12393;
b2=9.4153;
b3=-2.99880;
b4=0.51382;
b5=-.000018684;
c0=6.6334;
c1=-0.0035686;
C2=0.000000016682;
c3=0.00000000025611;
c4=-0.000000000000026558;
if(tep<=750)
{
d0=4.7869;
d1=-0.06953;
d2=0.000295775;
d3=-0.000000425732;
d4=0.000000000202894;
}
else
if(tep>750)
{
d0=10.09;
d1=-0.01183;
d2=0.0000047753;
d3=-0.000000000587209;
d4=-0.000000000000025334;
}
for(i=0;i<14;i++)
{
sum=sum+C_YI(c,t,i)/MW[i];
}
MWmix=1/sum;
XH2O=C_YI(c,t,9)*MWmix/18;
Xco=C_YI(c,t,10)*MWmix/28;
XCO2=C_YI(c,t,3)*MWmix/44;
pH2O=XH2O*Pamb;
pco=Xco*Pamb;
pCO2=XCO2*Pamb;
absCO2=a0+(a1*(1000/tep))+(a2*pow(1000/tep,2))+(a3*pow(1000/tep,3))+(a4*pow(1000/tep,4))+(a5*pow(1000/tep,5));
absco=d0+(d1*tep)+(d2*pow(tep,2))+(d3*pow(tep,3))+ (d4*pow(tep,4));
absH2O=b0+(b1*(1000/tep))+(b2*pow(1000/tep,2))+(b3*pow(1000/tep,3))+(b4*pow(1000/tep,4))+(b5*pow(1000/tep,5));
kapa=(absco*pco)+(absCO2*pCO2)+(absH2O*pH2O);
source=-(4*sigma*kapa*(pow(tep,4)-pow(tamb,4)));
ds[eqn]=0;
/*fprintf(fp,"abc");
fclose(fp);*/
return source;
}

[hbilal1076]

When I click on calculate it start processing and after 2 second this error appeared in console and the fluent get crashed and disappeared and closed to the main window (main window I means where mesh, setup, result etc. are listed.

[AlexanderZ]

remove this line

if(tep>750)

problem could be with mass fraction :

sum=sum+C_YI(c,t,i)/MW[i];
and
XH2O=C_YI(c,t,9)*MWmix/18;
Xco=C_YI(c,t,10)*MWmix/28;
XCO2=C_YI(c,t,3)*MWmix/44;

check carefully IDs of fractions 9, 10 and 3
if I were you I would print in console variable to check if they are defined properly

for(i=0;i<14;i++)
{
Message0("current sum -> %f, current mass -> %f, of fraction ->%d",sum,C_YI(c,t,i),i);
sum=sum+C_YI(c,t,i)/MW[i];
};

[hbilal1076]

Dear Prof. AlexanderZ,

I removed

if(tep>750)

but still the same error, also you mentioned the problem in mass fraction but I don't know what will be the problem to edit?

Thank you
Bilal

[AlexanderZ]

print in console variable to check if they are defined properly

edit this part of code as following:

for(i=0;i<14;i++)
{
Message0("current sum -> %f, current mass -> %f, of fraction ->%d",sum,C_YI(c,t,i),i);
sum=sum+C_YI(c,t,i)/MW[i];
};

show the console output

[hbilal1076]

Dear Prof. AlexanderZ,
I edited and used the below, but again the same Error.
For your convenience, I attached the error screen shot.


#include "udf.h"
DEFINE_SOURCE(energy,c,t,ds,eqn)
{
/*FILE *fp;*/
real source,tep,sigma,Pamb,tamb;
real MW[14];
real XH2O,Xco,XCO2,pH2O,pco,pCO2;
real MWmix,sum=0;
real kapa,absH2O,absco,absCO2;
real a0,a1,a2,a3,a4,a5;
real b0,b1,b2,b3,b4,b5;
real c0,c1,C2,c3,c4;
real d0,d1,d2,d3,d4;
int i;
/*fp=fopen("properties.txt","a+");*/
tep=C_T(c,t);
MW[0]=2;
MW[1]=1;
MW[2]=40;
MW[3]=44;
MW[4]=4;
MW[5]=16;
MW[6]=17;
MW[7]=29;
MW[8]=33;
MW[9]=18;
MW[10]=28;
MW[11]=32;
MW[12]=34;
MW[13]=28;
sigma=0.000000056697;
Pamb=1.0;
tamb=298.0;
a0=18.741;
a1=-121.310;
a2=273.500;
a3=-194.05;
a4=56.31;
a5=-5.8169;
b0=-0.23093;
b1=1.12393;
b2=9.4153;
b3=-2.99880;
b4=0.51382;
b5=-.000018684;
c0=6.6334;
c1=-0.0035686;
C2=0.000000016682;
c3=0.00000000025611;
c4=-0.000000000000026558;
if(tep<=750)
{
d0=4.7869;
d1=-0.06953;
d2=0.000295775;
d3=-0.000000425732;
d4=0.000000000202894;
}
else
{
d0=10.09;
d1=-0.01183;
d2=0.0000047753;
d3=-0.000000000587209;
d4=-0.000000000000025334;
}
for(i=0;i<14;i++)
{
Message0("current sum -> %f, current mass -> %f, of fraction ->%d",sum,C_YI(c,t,i),i);
sum=sum+C_YI(c,t,i)/MW[i];
};
MWmix=1/sum;
XH2O=C_YI(c,t,9)*MWmix/18;
Xco=C_YI(c,t,10)*MWmix/28;
XCO2=C_YI(c,t,3)*MWmix/44;
pH2O=XH2O*Pamb;
pco=Xco*Pamb;
pCO2=XCO2*Pamb;
absCO2=a0+(a1*(1000/tep))+(a2*pow(1000/tep,2))+(a3*pow(1000/tep,3))+(a4*pow(1000/tep,4))+(a5*pow(1000/tep,5));
absco=d0+(d1*tep)+(d2*pow(tep,2))+(d3*pow(tep,3))+ (d4*pow(tep,4));
absH2O=b0+(b1*(1000/tep))+(b2*pow(1000/tep,2))+(b3*pow(1000/tep,3))+(b4*pow(1000/tep,4))+(b5*pow(1000/tep,5));
kapa=(absco*pco)+(absCO2*pCO2)+(absH2O*pH2O);
source=-(4*sigma*kapa*(pow(tep,4)-pow(tamb,4)));
ds[eqn]=0;
/*fprintf(fp,"abc");
fclose(fp);*/
return source;
}

[hbilal1076]

In Ansys fluent, as I am burning acetylene in oxygen rich region that give a product of H2O and CO2.
Therefore, I think my species order is C2H2,O2,H2O,CO2 shown in screenshot but the UDF I am using contain the species order of CO,CO2,H2O, already pasted/shared above, so is this the mistake I am doing?
If this is the mistake then I have to add variable for C2H2 and O2 also?

Actually I am trying to find the temperature and mole fraction of CO2 and H2O for each Grid, therefore my question is
(1) should I just need to remove the species CO from the above shared UDF code and no need to add C2H2 and O2?
(2) or remove the specie CO and add C2H2 and O2 to the above code?
Your comment/assistance will be highly appreciated
TIA