[kbaker]

Hello I am using the transport species model and I want to define the density of mixture as a UDF in terms of temperature and concentration as the definition on the picture, but I do not know how I can write the macro of concentrations may somebody help with it I am so grateful for that?

Khalid

[gearboy]

Originally Posted by kbaker

Hello I am using the transport species model and I want to define the density of mixture as a UDF in terms of temperature and concentration as the definition on the picture, but I do not know how I can write the macro of concentrations may somebody help with it I am so grateful for that?

Khalid

C_YI can get the mass fraction of a species. C_R gets the mixture density. So C_R(c,t)*C_YI(c,t,iSpecies) is just the concentration of iSpecies, unit is kg/m3.

[kbaker]

Thanks a lot gearboy for the reply. Actually I am little confused about your answer, the UDF I want to use is for the mixture density (i.e. C_R(c,t)? so how I can use it again as C_R(c,t)*C_YI(c,t,iSpecies) inside the definition?

Khalid

[gearboy]

Originally Posted by kbaker

Thanks a lot gearboy for the reply. Actually I am little confused about your answer, the UDF I want to use is for the mixture density (i.e. C_R(c,t)? so how I can use it again as C_R(c,t)*C_YI(c,t,iSpecies) inside the definition?

Khalid

I mean the value of C_R(c,t) is the mixture density (kg/m3). C_YI(c,t,i) is the mass fraction of species index i in the mixture (kg/kg mixture).

[kbaker]

Yes I aware that but I cannot imagine how to define the density of mixture as C_R(c,t) then used the same macro inside the same definition? Can you please write to me the definition I sent and send me it here? I am so grateful for that?


Khalid

[gearboy]

Originally Posted by kbaker

Yes I aware that but I cannot imagine how to define the density of mixture as C_R(c,t) then used the same macro inside the same definition? Can you please write to me the definition I sent and send me it here? I am so grateful for that?


Khalid

C_R(c,t) is a read-only value that gets the mixture density in Fluent, not defined by yourself.

[kbaker]

Originally Posted by gearboy

C_R(c,t) is a read-only value that gets the mixture density in Fluent, not defined by yourself.

I wrote the UDF for the definition for density of mixture? but some errors appeared to me while I interpreted it as below :

D:\\Kolsi\\den.C:15: macro `C_YI' used with only 2 args
temp definition shadows previous definition
Error: D:\\Kolsi\\den.C: line 11: parse error.
Error: D:\\Kolsi\\den.C: line 12: parse error.
Error: D:\\Kolsi\\den.C: line 13: m_t: undeclared variable

Here is the UDF


#include "udf.h"
DEFINE_PROPERTY(cell_density, cell, thread)
{
real rhm,rho,To,Co,betaT,betaC;
real temp = C_T(cell, thread);
rho= 1.16;
Co=0.35;
To=300;
betaT=3.33e-3;
betaC=-0.34;
cell_t cell;
Thread *m_t; /*mixture thread*/
begin_c_loop_all (cell,m_t)
{
rhm = rho*(betaT*(temp-To)-betaC*(C(R,T)*C_YI(c,m_t)-Co)); /* density of mixture */
}
end_c_loop_all (cell,m_t)
return rhm;
}

[gearboy]

Originally Posted by kbaker

I wrote the UDF for the definition for density of mixture? but some errors appeared to me while I interpreted it as below :

D:\\Kolsi\\den.C:15: macro `C_YI' used with only 2 args
temp definition shadows previous definition
Error: D:\\Kolsi\\den.C: line 11: parse error.
Error: D:\\Kolsi\\den.C: line 12: parse error.
Error: D:\\Kolsi\\den.C: line 13: m_t: undeclared variable

Here is the UDF


#include "udf.h"
DEFINE_PROPERTY(cell_density, cell, thread)
{
real rhm,rho,To,Co,betaT,betaC;
real temp = C_T(cell, thread);
rho= 1.16;
Co=0.35;
To=300;
betaT=3.33e-3;
betaC=-0.34;
cell_t cell;
Thread *m_t; /*mixture thread*/
begin_c_loop_all (cell,m_t)
{
rhm = rho*(betaT*(temp-To)-betaC*(C(R,T)*C_YI(c,m_t)-Co)); /* density of mixture */
}
end_c_loop_all (cell,m_t)
return rhm;
}

Put all variable definition before any operation. At least I found you defined "Thread *m_t" after "betaT=3.33e-3;" It's not allowed in pure C programming. And change "temp" to another name.

[kbaker]

I did that and also correct the mass fraction macro to C_R(c,t) it mentioned incorrectly but there is still error sticky with me:
Error: D:\Kolsi\\density.txt: line 14: t: undeclared variable

Here is the UDF
#include "udf.h"
DEFINE_PROPERTY(cell_density, cell, thread)
{
Thread *m_t; /*mixture thread*/
real rhm,rho,To,Co,betaT,betaC;
real T= C_T(cell, thread);
rho= 1.16;
Co=0.35;
To=300;
betaT=3.33e-3;
betaC=-0.34;
begin_c_loop_all (cell,m_t)
{
rhm = rho*(betaT*(T-To)-betaC*(C_R(c,t)*C_YI(c,t,0)-Co)); /* density of mixture */
}
end_c_loop_all (cell,m_t)
return rhm;
}

[gearboy]

"m_t" and "t" has no value in your code. Use "thread" from FLUENT instead.

Please read UDF manual carefully. Your basic concepts are not clear.

Originally Posted by kbaker

I did that and also correct the mass fraction macro to C_R(c,t) it mentioned incorrectly but there is still error sticky with me:
Error: D:\Kolsi\\density.txt: line 14: t: undeclared variable

Here is the UDF
#include "udf.h"
DEFINE_PROPERTY(cell_density, cell, thread)
{
Thread *m_t; /*mixture thread*/
real rhm,rho,To,Co,betaT,betaC;
real T= C_T(cell, thread);
rho= 1.16;
Co=0.35;
To=300;
betaT=3.33e-3;
betaC=-0.34;
begin_c_loop_all (cell,m_t)
{
rhm = rho*(betaT*(T-To)-betaC*(C_R(c,t)*C_YI(c,t,0)-Co)); /* density of mixture */
}
end_c_loop_all (cell,m_t)
return rhm;
}