CFD Online Discussion Forums - temperature profile variation -UDF

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temperature profile variation -UDF

Does fluent allow the external temperature function to be defined "by branches": i.e. one equation for 0<t<10000s and another for t>10000s for example. This way, the fitting would become much easier with distinct equations for distinct branches of time…

I have this code but it has only one fitting curve equation, while I have two equations for distinct times. how to do this ?

Code:

/***********************************************************************

udfexample.c 

UDF for specifying transient temperature profile boundary condition

 ************************************************************************/

#include "udf.h"

#include "mem.h"

DEFINE_PROFILE(Temp_Profile, thread, position)    

{

real x[ND_ND];                                       

real y; 

real theProfile;

face_t f;

begin_f_loop(f, thread);

 {

 F_CENTROID(x,f,thread);

 y = CURRENT_TIME;    

  theProfile=(283.7656)+25.44573*exp(-0.5*((y-49657.42)*(y-49657.42)/(11529.66*11529.66))); 

 F_PROFILE(f, thread, position) =theProfile;

 }

end_f_loop(f,thread)

}

regards,

See Added part to your code (in red)

Quote:

Originally Posted by ahvz (Post 431583)

Code:

/***********************************************************************

udfexample.c 

UDF for specifying transient temperature profile boundary condition

 ************************************************************************/

#include "udf.h"

#include "mem.h"

DEFINE_PROFILE(Temp_Profile, thread, position)    

{

real x[ND_ND];                                       

real y; 

real t1; //time whre your equation profile changes

real theProfile;

face_t f;

begin_f_loop(f, thread);

 {

 F_CENTROID(x,f,thread);

 y = CURRENT_TIME;    

if(y<t1)

  theProfile=(283.7656)+25.44573*exp(-0.5*((y-49657.42)*(y-49657.42)/(11529.66*11529.66))); 

 F_PROFILE(f, thread, position) =theProfile;

else

theProfile=other expressions

 F_PROFILE(f, thread, position) =theProfile;

 }

end_f_loop(f,thread)

}

regards,

I tried to change the domain of my temperature profile by defining time limits:

but the results are very strange. is the code written properly ?

Code:

/***********************************************************************

udfexample.c 

UDF for specifying transient temperature profile boundary condition

 ************************************************************************/

#include "udf.h"

#include "mem.h"

DEFINE_PROFILE(Temp_Profile, thread, position)    

{

real x[ND_ND];                                       

real y; 

real t1=32399;

real t2=89999;

real t3=118799;

real theProfile;

face_t f;

begin_f_loop(f, thread);

 {

 F_CENTROID(x,f,thread);

 y = CURRENT_TIME;     

if(y<=t1) 

   

       theProfile=(-3e-12*pow(y,3.))+(1e-7*pow(y,2.))-(-0.0004*pow(y,1.))+(282.08);

       F_PROFILE(f, thread, position) =theProfile;    

      {

     if(t1<y<=t2)

       theProfile=(-3e-13*pow(y,3.))+(7e-8*pow(y,2.))-(0.0055*pow(y,1.))+426.51;

       F_PROFILE(f, thread, position) =theProfile;

      }

      {

      if(t2<y<=t3)

      theProfile=(-2e-12*pow(y,3.))+(6e-7*pow(y,2.))-(0.0587*pow(y,1.))+2143.9;

      F_PROFILE(f, thread, position) =theProfile;

      }

      {

      if(y>t3)

      theProfile=(-4e-13*pow(y,3.))-(2e-7*pow(y,2.))-(0.0301*pow(y,1.))+1881.6;

      F_PROFILE(f, thread, position) =theProfile;

      }

 }

end_f_loop(f,thread)

}

regards,

hi

I need a udf for a work.I'm quite new in this area, so i really need your help. i need a linear varying temperature profile boundary condition to be applied on a circular face of a cylinder. temperature varies from 25 to 50 degrees from bottom to top of circle. diameter of circle is 470 mm . can you please help???