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problem in transcient heat flux b.c in UDF

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Old   April 8, 2003, 09:29
Default problem in transcient heat flux b.c in UDF
  #1
phani
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i am simualating solidification and melting problems in the fluent6.0,so for that i have to give heat flux boundary condition varing with time. So i have written the Udf for that but it is diverging after time (15sec) it is diverging in the third condition of the udf.So could u plz help me

#include "udf.h"

#define d 0.04 #define C 2.18844 #define D -0.602603 #define A 762.048e04 #define B -0.217412 #define den 8960 #define kc 363 #define cp 423

DEFINE_PROFILE(heat_flux, thread,position) {

real alpha, qmax,q;

face_t f;

alpha=kc/(den*cp);

qmax=A*pow(d/alpha,B);

begin_f_loop(f,thread) { real t=RP_Get_Real("flow-time");

if(t<=5)

F_PROFILE(f,thread,position) = qmax;

else if((t>5)&&(t<=15))

F_PROFILE(f,thread,position) = qmax-6.5715e4*(t-5);

else

F_PROFILE(f,thread,position) =- 2.0152e6*C*pow(t,-D)/(pow(alpha,0.05));

} end_f_loop(f,thread) }

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Old   April 8, 2003, 10:43
Default Re: problem in transcient heat flux b.c in UDF
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Alex Munoz
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hello

Couple of mistakes

All the number must to have the form 5. or 5.0 not the form 5 in order to assign the decimal number.

also you don't need to write this sentences like this else if((t>5)&&(t<=15)) you can write the sentes like this else if(t<=15.0) F_PROFILE(f,thread,position) = qmax-6.5715e4*(t-5.0);

Best Regards

Alex Munoz
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Old   April 9, 2003, 00:13
Default Re: problem in transcient heat flux b.c in UDF
  #3
phani
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Hai Alex,

thank's for responding,i did what u said, again the solution is diverging at the third condition i.e [F_PROFILE(f,thread,position) =- 2.0152e6*C*pow(t,-D)/(pow(alpha,0.05));] when the fluent is solving the above equation, and the solution is get diverging.
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Old   April 9, 2003, 00:58
Default Re: problem in transcient heat flux b.c in UDF
  #4
Alex Munoz
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Hi

It is correct that you define D=-### and then in your function you writhe pow(t,-D)?

I wonder if you are making -*-=+

In addition how do you know that fluent is diverging in the third condition, the code is not able to tell you that type of information.

Just it has divergence but how you can ensure that it is due to the UDF??

Regards

Alex
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