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unsteady inlet velocity udf

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Old   December 4, 2004, 09:15
Default unsteady inlet velocity udf
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jill
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The udf i am using for my inlet is similar to that of the "unsteady flow in a tube" example from the user's guide. I am modeling a "T" intersection where there are two inlets with different velocity profiles. i have created two udf's and they both compile using the interpreted udf. the problem that i encounter is when i try to set up the bc's. it seems as though i am not able to use both udf's at the same time (one for inlet A and the other for inlet B). If I compile the udf for inlet A and set up the bc everything works fine but then if i try to compile the udf for inlet B I get, "Error: chip exec: function XXX not found". If i try to compile both of them and then set the bc's only the later of the two are in the pulldowns. Can anyone help me? Thank you.

jill
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Old   December 4, 2004, 09:47
Default Re: unsteady inlet velocity udf
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Luca
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Maybe I have misunderstood but I think you should compile your 2 UDFs in a single file. So put your code in 1 file and compile it. Then you can hook both of them.Luca
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Old   December 4, 2004, 09:55
Default Re: unsteady inlet velocity udf
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jill
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No you didn't misunderstand....your response makes a lot of sense and it works now. Thank you very much.
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Old   December 4, 2004, 09:56
Default Re: unsteady inlet velocity udf
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you're welcome. Luca
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Old   February 9, 2015, 07:22
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Hi. I am not very good at programming. Like the case above was solved by combining the two program in one file. But I do not know how to combine it in one file. Here is my 2 program files,

#include "udf.h"
#define T_HOT 306.0
#define T_COLD 300.0
#define KTC_HOT 0.66 /* High thermal conductivity when hot */
#define KTC_COLD 0.64 /* Low thermal conductivity when cold */

DEFINE_PROPERTY(fmwcnt_thermal_conductivity, c, ct)
{
real temp, ktc_turbulent;

temp = C_T(c,ct);

if (temp == T_HOT)
ktc_turbulent = KTC_HOT;

else if (temp == T_COLD)
ktc_turbulent = KTC_COLD;

else
ktc_turbulent = KTC_COLD + (temp - T_COLD)*
(KTC_HOT - KTC_COLD)/(T_HOT - T_COLD);

return ktc_turbulent;
}


Here is the second program,
#include "udf.h"
#define T_HOT 306.0
#define T_COLD 300.0
#define MU_HOT 7.81e-4 /* Low viscosity when hot */
#define MU_COLD 8.81e-4 /* High viscosity when cold */

DEFINE_PROPERTY(fmwcnt_viscosity, c, ct)
{
real temp, mu_turbulent;

temp = C_T(c,ct);

if (temp == T_HOT)
mu_turbulent = MU_HOT;

else if (temp == T_COLD)
mu_turbulent = MU_COLD;

else
mu_turbulent = MU_COLD + (temp - T_COLD)*
(MU_HOT - MU_COLD)/(T_HOT - T_COLD);

return mu_turbulent;
}



Thanks
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Old   February 9, 2015, 09:13
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Hi,

Basically combining it in one file just means
- 1 set of headers and define functions
- 2 functions put in the body.

So for you that would give:

Code:
#include "udf.h" 
#define T_HOT 306.0
#define T_COLD 300.0
#define KTC_HOT 0.66 /* High thermal conductivity when hot */ 
#define KTC_COLD 0.64 /* Low thermal conductivity when cold */ 
#define MU_HOT 7.81e-4 /* Low viscosity when hot */ 
#define MU_COLD 8.81e-4 /* High viscosity when cold */ 

DEFINE_PROPERTY(fmwcnt_thermal_conductivity, c, ct) 
{ 
real temp, ktc_turbulent; 

temp = C_T(c,ct); 

if (temp == T_HOT) 
ktc_turbulent = KTC_HOT; 

else if (temp == T_COLD) 
ktc_turbulent = KTC_COLD; 

else 
ktc_turbulent = KTC_COLD + (temp - T_COLD)* 
(KTC_HOT - KTC_COLD)/(T_HOT - T_COLD); 

return ktc_turbulent; 
}

DEFINE_PROPERTY(fmwcnt_viscosity, c, ct) 
{ 
real temp, mu_turbulent; 

temp = C_T(c,ct); 

if (temp == T_HOT) 
mu_turbulent = MU_HOT; 

else if (temp == T_COLD) 
mu_turbulent = MU_COLD; 

else 
mu_turbulent = MU_COLD + (temp - T_COLD)* 
(MU_HOT - MU_COLD)/(T_HOT - T_COLD); 

return mu_turbulent; 
}
Then, save this whole thing under one name and compile in FLUENT. FLUENT will recognize it's actually 2 different UDFs.
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Old   February 9, 2015, 09:16
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Hi,
simply put them in one files, and do not duplicate headers files (.h) and global variables:

Code:
#include "udf.h"
#define T_HOT 306.0
#define T_COLD 300.0
#define KTC_HOT 0.66 /* High thermal conductivity when hot */
#define KTC_COLD 0.64 /* Low thermal conductivity when cold */
#define MU_HOT 7.81e-4 /* Low viscosity when hot */
#define MU_COLD 8.81e-4 /* High viscosity when cold */

DEFINE_PROPERTY(fmwcnt_thermal_conductivity, c, ct)
{
real temp, ktc_turbulent;

temp = C_T(c,ct);

if (temp == T_HOT)
   ktc_turbulent = KTC_HOT;

else if (temp == T_COLD)
   ktc_turbulent = KTC_COLD;

else
   ktc_turbulent = KTC_COLD + (temp - T_COLD)*(KTC_HOT - KTC_COLD)/(T_HOT - T_COLD);

return ktc_turbulent;
}


DEFINE_PROPERTY(fmwcnt_viscosity, c, ct)
{
real temp, mu_turbulent;

temp = C_T(c,ct);

if (temp == T_HOT)
  mu_turbulent = MU_HOT;

else if (temp == T_COLD)
  mu_turbulent = MU_COLD;

else
  mu_turbulent = MU_COLD + (temp - T_COLD)*(MU_HOT - MU_COLD)/(T_HOT - T_COLD);

return mu_turbulent;
}
Hihi too late
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Old   February 10, 2015, 03:47
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Thanks CeesH and ghost82. The UDF can run by interpreted and it gives what I want. But I cant compiled due to the path error. Izzit compulsory to compiled it?

Thanks
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Old   February 10, 2015, 07:04
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It is not mandatory to compile this udf. You can interpret it without problems.
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