[ngonbadipoor@yahoo.com]

Hi

I am not familiar with C language for UDF code, I need your help to define a code for the attached correlation of thermal conductivity depend on density, volume fraction, temp., Prandtl Number and Brinkman Number.
Please let me know if you have any suggestion .
I attached the correlation.
Thanks

[Bruno Machado]

Originally Posted by ngonbadipoor@yahoo.com

Hi

I am not familiar with C language for UDF code, I need your help to define a code for the attached correlation of thermal conductivity depend on density, volume fraction, temp., Prandtl Number and Brinkman Number.
Please let me know if you have any suggestion .
I attached the correlation.
Thanks

I suggest you to read the manual and use its examples as a base for your code.

[ngonbadipoor@yahoo.com]

hi
how could i loop all the zone to specify the conductivity function.

[pakk]

Did you look in the manual to see how they specify conductivity in a udf?

[ngonbadipoor@yahoo.com]

Hi
I wrote this : could you please advise me>

DEFINE_PROPERTY(knew,c,t)
{
real knf;
real pos[ND_ND];
real y;
real fip; /* volume concentration*/
real ronf; /* density of nanofluid*/
real robf; /* density of base fluid*/
real rop; /* density of particle*/
real cpp; /*specific heat of particle*/
real cpbf; /* specific heat of base fluid*/
real cpnf; /* specific heat of nanofluid*/
real a;
real b;
real dp; /* nanoparticle size*/
real Rep; /* reynolds number of particle*/
real kp; /* thermal conductivity of particle*/
real nunf; /*the viscosity of nanofluids*/
real NBRp; /* Brinkman number*/
Domain *d;
Thread *t;
cell_t c;
real temp = C_T(c,t);
thread_loop_c(t,d)
{
begin_c_loop(c,t)
{

cpnf= (fip*rop*cpp+(1-fip)*robf*cpbf)/(ronf); /* specific heat of nanofluid*/
nunf=-0.3513+0.462*fip-0.135*fip*fip+0.0125*fip*fip*fip
+(24.662+2.316*fip-0.4959*fip*fip)/(temp-273)+30.979*(fip*fip)/((temp-273)*(temp-273))
+(995.388-3205.016*fip+8.667*fip*fip)/((temp-273)*(temp-273)*(temp-273))+
(fip/(dp*dp))*(dp*(3.937-1.194*fip)+fip*(20.502-0.8086*fip));
/* viscosity of nanofluid which depends on nanoparticle size and temperature */
prp=(nubf*cpp/kp); /* prandtl of particle*/
prbf= nubf*cpbf/kbf; /* prandtl of base fluid*/
a= -3.516+0.0227*temp-0.000036*temp*temp+(105.1-0.691*temp+0.0011*temp*temp)/(dp)+36.63/(dp*dp);
/* a is a function of teprature and nanoparticle size*/
b= (-5.095+8.181* fip-0.066*fip*fip)/(dp);
NBRp= double sqrt (double nubf*V*V/(kp*temp)) ;
knf=1.698*pow (fip, a) * pow ((temp/273),b)* pow (prp,0.0645)* pow(prbf,-0.106 )* pow (Rep/pow (NBRp,0.5), -0.00463)* kbf; /*thermal conductivity of nanofluid*/


}
end_c_loop(c,t)
}

return ktc;
}

[pakk]

Advise: try it in Fluent and see if it does what you want.

[ngonbadipoor@yahoo.com]

hi, the errors are: i gave some values to constants but only viscosity, a, b, and thermal conductivity must be calculated.
Error: C:\\Users\\pc\\Desktop\\thermal con.c: line 1: parse error.

Error: GENERAL-CAR-CDR: invalid argument [1]: improper list
Error Object: ()

[Bruno Machado]

Originally Posted by ngonbadipoor@yahoo.com

hi, the errors are: i gave some values to constants but only viscosity, a, b, and thermal conductivity must be calculated.
Error: C:\\Users\\pc\\Desktop\\thermal con.c: line 1: parse error.

Error: GENERAL-CAR-CDR: invalid argument [1]: improper list
Error Object: ()

first, your UDF should start with

#include "udf.h"

second, in the list of variables you created, you basically said that those variables exist, but no value were assigned for it.

third, there is no need to loop throught all the thread and cells. The DEFINE_PROPERTY does it automatically (this is said in the manual)

fourth, in the following line, there is no need to say it is double (again).

NBRp= double sqrt (double nubf*V*V/(kp*temp)) ;

These are the things that I noticed overlooking your UDF. Change it, try it again and see what happens.

[ngonbadipoor@yahoo.com]

Hi
Thanks,
I did what you said here are the errors:

t definition shadows previous definition
c definition shadows previous definition
Error: C:\\Users\\pc\\Desktop\\thermal con.c: line 38: parse error.
Error: C:\\Users\\pc\\Desktop\\thermal con.c: line 39: parse error.

i put no loop this time.

[Bruno Machado]

Originally Posted by ngonbadipoor@yahoo.com

Hi
Thanks,
I did what you said here are the errors:

t definition shadows previous definition
c definition shadows previous definition
Error: C:\\Users\\pc\\Desktop\\thermal con.c: line 38: parse error.
Error: C:\\Users\\pc\\Desktop\\thermal con.c: line 39: parse error.

there is no need to define cell and thread again. these are values provided by the macro.

[ngonbadipoor@yahoo.com]

there is no loop any more, but still the errors are the same as the last time.
#include "udf.h"
DEFINE_PROPERTY(knew,c,t)
{
real knf;
real pos[ND_ND];
real V=1;
real fip=0.01; /* volume concentration*/
real ronf=1027; /* density of nanofluid*/
real robf=1000; /* density of base fluid*/
real rop=3720; /* density of particle*/
real cpp=1; /*specific heat of particle*/
real cpbf=.5; /* specific heat of base fluid*/
real cpnf=257.6; /* specific heat of nanofluid*/
real a;
real b;
real dp=40e-9; /* nanoparticle size*/
real Rep=1000; /* reynolds number of particle*/
real kp=18; /* thermal conductivity of particle*/
real nunf; /*the viscosity of nanofluids*/
real NBRp; /* Brinkman number*/
real nubf=8.9e-4;
real kbf=0.6;
Domain *d;
Thread *t;
cell_t c;
real temp = C_T(c,t);



/* cpnf= (fip*rop*cpp+(1-fip)*robf*cpbf)/(ronf); specific heat of nanofluid*/
nunf=-0.3513+0.462*fip-0.135*fip*fip+0.0125*fip*fip*fip
+(24.662+2.316*fip-0.4959*fip*fip)/(temp-273)+30.979*(fip*fip)/((temp-273)*(temp-273))
+(995.388-3205.016*fip+8.667*fip*fip)/((temp-273)*(temp-273)*(temp-273))+
(fip/(dp*dp))*(dp*(3.937-1.194*fip)+fip*(20.502-0.8086*fip));
/* viscosity of nanofluid which depends on nanoparticle size and temperature */
real prp=(nubf*cpp/kp); /* prandtl of particle*/
real prbf= nubf*cpbf/kbf; /* prandtl of base fluid*/
a= -3.516+0.0227*temp-0.000036*temp*temp+(105.1-0.691*temp+0.0011*temp*temp)/(dp)+36.63/(dp*dp);
/* a is a function of teprature and nanoparticle size*/
b= (-5.095+8.181* fip-0.066*fip*fip)/(dp);
NBRp= sqrt ( nubf*V*V/(kp*temp)) ;
knf=1.698*pow (fip, a) * pow ((temp/273),b)* pow (4,0.0645)* pow(5,-0.106 )* pow (Rep/pow (NBRp,0.5), -0.00463)* kbf; /*thermal conductivity of nanofluid*/




return knf;
}

[Bruno Machado]

Originally Posted by ngonbadipoor@yahoo.com

there is no loop any more, but still the errors are the same as the last time.
#include "udf.h"
DEFINE_PROPERTY(knew,c,t)
{
real knf;
real pos[ND_ND];
real V=1;
real fip=0.01; /* volume concentration*/
real ronf=1027; /* density of nanofluid*/
real robf=1000; /* density of base fluid*/
real rop=3720; /* density of particle*/
real cpp=1; /*specific heat of particle*/
real cpbf=.5; /* specific heat of base fluid*/
real cpnf=257.6; /* specific heat of nanofluid*/
real a;
real b;
real dp=40e-9; /* nanoparticle size*/
real Rep=1000; /* reynolds number of particle*/
real kp=18; /* thermal conductivity of particle*/
real nunf; /*the viscosity of nanofluids*/
real NBRp; /* Brinkman number*/
real nubf=8.9e-4;
real kbf=0.6;
Domain *d;
Thread *t;
cell_t c;
real temp = C_T(c,t);



/* cpnf= (fip*rop*cpp+(1-fip)*robf*cpbf)/(ronf); specific heat of nanofluid*/
nunf=-0.3513+0.462*fip-0.135*fip*fip+0.0125*fip*fip*fip
+(24.662+2.316*fip-0.4959*fip*fip)/(temp-273)+30.979*(fip*fip)/((temp-273)*(temp-273))
+(995.388-3205.016*fip+8.667*fip*fip)/((temp-273)*(temp-273)*(temp-273))+
(fip/(dp*dp))*(dp*(3.937-1.194*fip)+fip*(20.502-0.8086*fip));
/* viscosity of nanofluid which depends on nanoparticle size and temperature */
real prp=(nubf*cpp/kp); /* prandtl of particle*/
real prbf= nubf*cpbf/kbf; /* prandtl of base fluid*/
a= -3.516+0.0227*temp-0.000036*temp*temp+(105.1-0.691*temp+0.0011*temp*temp)/(dp)+36.63/(dp*dp);
/* a is a function of teprature and nanoparticle size*/
b= (-5.095+8.181* fip-0.066*fip*fip)/(dp);
NBRp= sqrt ( nubf*V*V/(kp*temp)) ;
knf=1.698*pow (fip, a) * pow ((temp/273),b)* pow (4,0.0645)* pow(5,-0.106 )* pow (Rep/pow (NBRp,0.5), -0.00463)* kbf; /*thermal conductivity of nanofluid*/




return knf;
}

This part is useless and it is causing your error

Domain *d;
Thread *t;
cell_t c;

[ngonbadipoor@yahoo.com]

thanks for your reply, what are this 2 errors?
Error: C:\\Users\\pc\\Desktop\\thermal con2.c: line 34: parse error.
Error: C:\\Users\\pc\\Desktop\\thermal con2.c: line 35: parse error.

[pakk]

It means there are problems on lines 34 and 35. Count in your script to see which lines these are.

[ngonbadipoor@yahoo.com]

thanks
when there is 2 function, eg. one for conductivity and the other one for viscosity. I define 2 different UDF for each one, when i interpret them; it only could find one of the function in the material property section.
when i run the solution the following message comes:
((Error: chip-exec: function "visco" not found.))
where visco is the other function name!
what is the problem?

[Bruno Machado]

Originally Posted by ngonbadipoor@yahoo.com

thanks
when there is 2 function, eg. one for conductivity and the other one for viscosity. I define 2 different UDF for each one, when i interpret them; it only could find one of the function in the material property section.
when i run the solution the following message comes:
((Error: chip-exec: function "visco" not found.))
where visco is the other function name!
what is the problem?

create everything in a single file. you can not interprete 2 different files.

[ngonbadipoor@yahoo.com]

Hi
I have problem in my udf.
1, as i only could interpret one udf to my solver for material property and i have 2 function (thermal conductivity and viscosity) ,is the following udf correct?

#include "udf.h"
DEFINE_PROPERTY(knew,c,t)
{
real knf;
real pos[ND_ND];
real V=0.05;
real fip=0.01; /* volume concentration*/
real ronf=1027; /* density of nanofluid*/
real robf=1000; /* density of base fluid*/
real rop=3720; /* density of particle*/
real cpp=1; /*specific heat of particle*/
real cpbf=.5; /* specific heat of base fluid*/
real cpnf=257.6; /* specific heat of nanofluid*/
real a;
real b;
real dp=40e-9; /* nanoparticle size*/
real Rep=1000; /* reynolds number of particle*/
real kp=18; /* thermal conductivity of particle*/
real nunf=C_MU_L(c,t); /*the viscosity of nanofluids*/
real NBRp; /* Brinkman number*/
real nubf=8.9e-4;
real kbf=0.6;
real prp=0.1; /* prandtl of particle*/
real prbf= 0.01; /* prandtl of base fluid*/
real tempo = C_T(c,t);




nunf=..... ; /* viscosity of nano fluid which depends on nano particle size and temperature */

a= ..... ; /* a is a function of temperature and nano particle size*/
b= ..... ;
NBRp= ..... ;
knf=..... /*thermal conductivity of nanofluid*/




return knf; /* for thermal conductivity*/
return nubf; /* for viscosity of nanofluid*/
}

2,

I am using following scheme for simulation
-Energy--on
-Steady
-Laminar viscosity
-SIMPLE
-Pressure based solver--
velocity inlet
-Outlet----Pressure outlet
-Mesh--Maximum Ortho Skew = 7.00310e-01

Maximum Aspect Ratio = 2.00322e+01

After doing all above stuff, solution is not proceeding ahead, facing errors like
# Divergence detected in AMG solver: temperature -> Increasing relaxation sweeps!
#reversed flow in 177 faces on pressure-outlet 7.
please advise me.



is that because of mesh size or relaxation factor? what should i do?
thanks

[`e`]

What is your complete UDF? Are you trying to return the thermal conductivity before the viscosity every time, or is this procedure different in your actual UDF?

[Bruno Machado]

Originally Posted by ngonbadipoor@yahoo.com

Hi
I have problem in my udf.
1, as i only could interpret one udf to my solver for material property and i have 2 function (thermal conductivity and viscosity) ,is the following udf correct?

#include "udf.h"
DEFINE_PROPERTY(knew,c,t)
{
real knf;
real pos[ND_ND];
real V=0.05;
real fip=0.01; /* volume concentration*/
real ronf=1027; /* density of nanofluid*/
real robf=1000; /* density of base fluid*/
real rop=3720; /* density of particle*/
real cpp=1; /*specific heat of particle*/
real cpbf=.5; /* specific heat of base fluid*/
real cpnf=257.6; /* specific heat of nanofluid*/
real a;
real b;
real dp=40e-9; /* nanoparticle size*/
real Rep=1000; /* reynolds number of particle*/
real kp=18; /* thermal conductivity of particle*/
real nunf=C_MU_L(c,t); /*the viscosity of nanofluids*/
real NBRp; /* Brinkman number*/
real nubf=8.9e-4;
real kbf=0.6;
real prp=0.1; /* prandtl of particle*/
real prbf= 0.01; /* prandtl of base fluid*/
real tempo = C_T(c,t);




nunf=..... ; /* viscosity of nano fluid which depends on nano particle size and temperature */

a= ..... ; /* a is a function of temperature and nano particle size*/
b= ..... ;
NBRp= ..... ;
knf=..... /*thermal conductivity of nanofluid*/




return knf; /* for thermal conductivity*/
return nubf; /* for viscosity of nanofluid*/
}

2,

I am using following scheme for simulation
-Energy--on
-Steady
-Laminar viscosity
-SIMPLE
-Pressure based solver--
velocity inlet
-Outlet----Pressure outlet
-Mesh--Maximum Ortho Skew = 7.00310e-01

Maximum Aspect Ratio = 2.00322e+01

After doing all above stuff, solution is not proceeding ahead, facing errors like
# Divergence detected in AMG solver: temperature -> Increasing relaxation sweeps!
#reversed flow in 177 faces on pressure-outlet 7.
please advise me.



is that because of mesh size or relaxation factor? what should i do?
thanks

You must have in the same file different DEFINE_PROPERTY for viscosity and thermal conductivity.

[ngonbadipoor@yahoo.com]

Hi
this is my UDF for a nano fluid :
#include "udf.h"
DEFINE_PROPERTY(knew,c,t)
{
real knf; /* nanofluid thermal conductivity*/
real pos[ND_ND];
real V=.05; /* V is the inlet velocity*/
real fip=0.01; /* volume concentration*/
real ronf=1027; /* density of nanofluid*/
real robf=1000; /* density of base fluid*/
real rop=3720; /* density of particle*/
real cpp=1; /*specific heat of particle*/
real cpbf=.5; /* specific heat of base fluid*/
real cpnf=257.6; /* specific heat of nanofluid*/
real a;
real b;
real dp=40e-9; /* nanoparticle size*/
real Rep=1000; /* reynolds number of particle*/
real kp=18; /* thermal conductivity of particle*/
real nunf=C_MU_L(c,t); /*the viscosity of nanofluids*/
real NBRp; /* Brinkman number*/
real nubf=8.9e-4;
real kbf=0.6;
real prp=0.1; /* prandtl of particle*/
real prbf= 0.01; /* prandtl of base fluid*/
real tempo = C_T(c,t);



/* cpnf= (fip*rop*cpp+(1-fip)*robf*cpbf)/(ronf); specific heat of nanofluid*/
nunf=-0.3513+0.462*fip-0.135*fip*fip+0.0125*fip*fip*fip
+(24.662+2.316*fip-0.4959*fip*fip)/(tempo-273)+30.979*(fip*fip)/((tempo-273)*(tempo-273))
+(995.388-3205.016*fip+8.667*fip*fip)/((tempo-273)*(tempo-273)*(tempo-273))+
(fip/(dp*dp))*(dp*(3.937-1.194*fip)+fip*(20.502-0.8086*fip));
/* viscosity of nanofluid which depends on nanoparticle size and temperature */

a= -3.516+0.0227*tempo-0.000036*tempo*tempo+(105.1-0.691*tempo+0.0011*tempo*tempo)/(dp)+36.63/(dp*dp);
/* a is a function of teprature and nanoparticle size*/
b= (-5.095+8.181* fip-0.066*fip*fip)/(dp);
NBRp= sqrt ( nubf*V*V/(kp*tempo)) ;
knf=1.698*pow (fip, a) * pow ((tempo/273),b)* pow (4,0.0645)* pow(5,-0.106 )* pow (Rep/pow (NBRp,0.5), -0.00463)* kbf; /*thermal conductivity of nanofluid*/




return knf;

}

DEFINE_PROPERTY(visco,c,t)
{
real knf;
real pos[ND_ND];
real V=.05;
real fip=0.01; /* volume concentration*/
real ronf=1027; /* density of nanofluid*/
real robf=1000; /* density of base fluid*/
real rop=3720; /* density of particle*/
real cpp=1; /*specific heat of particle*/
real cpbf=.5; /* specific heat of base fluid*/
real cpnf=257.6; /* specific heat of nanofluid*/
real a;
real b;
real dp=40e-9; /* nanoparticle size*/
real Rep=1000; /* reynolds number of particle*/
real kp=18; /* thermal conductivity of particle*/
real nunf=C_MU_L(c,t); /*the viscosity of nanofluids*/
real NBRp; /* Brinkman number*/
real nubf=8.9e-4;
real kbf=0.6;
real prp=0.1; /* prandtl of particle*/
real prbf= 0.01; /* prandtl of base fluid*/
real tempo = C_T(c,t);



/* cpnf= (fip*rop*cpp+(1-fip)*robf*cpbf)/(ronf); specific heat of nanofluid*/
nunf=-0.3513+0.462*fip-0.135*fip*fip+0.0125*fip*fip*fip
+(24.662+2.316*fip-0.4959*fip*fip)/(tempo-273)+30.979*(fip*fip)/((tempo-273)*(tempo-273))
+(995.388-3205.016*fip+8.667*fip*fip)/((tempo-273)*(tempo-273)*(tempo-273))+
(fip/(dp*dp))*(dp*(3.937-1.194*fip)+fip*(20.502-0.8086*fip));
/* viscosity of nanofluid which depends on nanoparticle size and temperature */

a= -3.516+0.0227*tempo-0.000036*tempo*tempo+(105.1-0.691*tempo+0.0011*tempo*tempo)/(dp)+36.63/(dp*dp);
/* a is a function of teprature and nanoparticle size*/
b= (-5.095+8.181* fip-0.066*fip*fip)/(dp);
NBRp= sqrt ( nubf*V*V/(kp*tempo)) ;
knf=1.698*pow (fip, a) * pow ((tempo/273),b)* pow (4,0.0645)* pow(5,-0.106 )* pow (Rep/pow (NBRp,0.5), -0.00463)* kbf; /*thermal conductivity of nanofluid*/





return nubf;
}
but it diverged:
# Divergence detected in AMG solver: temperature -> Increasing relaxation sweeps!
# You may try the enhanced divergence recovery with (rpsetvar 'amg/protective-enhanced? #t)

Error: Divergence detected in AMG solver: temperature

Error: Divergence detected in AMG solver: temperature
Error Object: #f
please help me