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-   -   Boundary condition temerature profile (https://www.cfd-online.com/Forums/fluent-udf/129436-boundary-condition-temerature-profile.html)

ahvz February 5, 2014 04:54
Boundary condition temerature profile
 
Hello,
I have been working on transient analysis with considering the below code but I have strange results. is there anyone to help me to find my problem?

(indeed I divide the temperature profile to some branches to get accurate fitting curve, that's why I have more than one equation in the code)

Code:
/***********************************************************************
UDF example.c
UDF for specifying transient temperature profile boundary condition S
 ************************************************************************/
#include "udf.h"
#include "mem.h"
DEFINE_PROFILE(TempS_Profile, thread, position)   
{
real x[ND_ND];                                     
real y;
real t1=10019;
real t2=13529;
real t3=20009;
real t4=29999;
real t5=40019;
real t6=50009;
real t7=59999;
real t8=70019;
real t9=80009;

real theProfile;
face_t f;
begin_f_loop(f, thread);
 {
 F_CENTROID(x,f,thread);
 y = CURRENT_TIME;   
 
    if(y<=t1)
      {     
      theProfile=(-2E-13*pow(y,3.))+(3E-08*pow(y,2.))+(9E-06*pow(y,1.))+283.78;
      F_PROFILE(f, thread, position) =theProfile;   
      }
      else if (y<=t2 && y>t1)
      {
      theProfile=(1E-11*pow(y,3.))-(4E-07*pow(y,2.))+(0.0061*pow(y,1.))+257.77; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t3 && y>t2)
      {
      theProfile=(-4E-11*pow(y,3.))+(2E-06*pow(y,2.))-(0.035*pow(y,1.))+482.71; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t4 && y>t3)
      {
      theProfile=(4E-12*pow(y,3.))-(3E-07*pow(y,2.))+(0.0091*pow(y,1.))+203.7; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t5 && y>t4)
      {
      theProfile=(-7E-12*pow(y,3.))+(7E-07*pow(y,2.))-(0.0233*pow(y,1.))+550.94; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t6 && y>t5)
      {
      theProfile=(9E-12*pow(y,3.))-(1E-06*pow(y,2.))+(0.0575*pow(y,1.))+566.62; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t7 && y>t6)
      {
      theProfile=(1E-12*pow(y,3.))-(2E-07*pow(y,2.))+(0.0094*pow(y,1.))+171.39; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t8 && y>t7)
      {
      theProfile=(-6E-12*pow(y,3.))+(1E-06*pow(y,2.))-(0.0849*pow(y,1.))+2180.8; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t9 && y>t8)
      {
      theProfile=(-1E-11*pow(y,3.))+(3E-06*pow(y,2.))-(0.2083*pow(y,1.))+5510.9; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else
      {
      theProfile=(-6E-11*pow(y,3.))+(1E-05*pow(y,2.))-(1.2143*pow(y,1.))+33813; 
      F_PROFILE(f, thread, position) =theProfile;
      }
 }
end_f_loop(f,thread)
}

regards,

pakk February 6, 2014 14:04
Your equations give the following profile:
Code:
#time #temperature
0 283.779999
1000 283.818787
2000 283.916412
3000 284.071594
4000 284.283203
5000 284.549988
6000 284.870789
7000 285.244385
8000 285.669586
9000 286.145203
10000 286.670013
11000 289.779999
12000 290.649994
13000 291.440002
14000 274.950012
15000 272.709991
16000 270.869995
17000 269.190002
18000 267.429993
19000 265.350006
20000 262.709991
21000 299.544006
22000 301.291992
23000 302.967987
24000 304.596008
25000 306.200012
26000 307.803986
27000 309.432007
28000 311.108002
29000 312.855988
30000 292.940002
31000 292.803009
32000 292.764008
33000 292.781006
34000 292.812012
35000 292.815002
36000 292.747986
37000 292.569000
38000 292.235992
39000 291.707001
40000 290.940002
41000 1863.409058
42000 1884.411987
43000 1905.682983
44000 1927.276001
45000 1949.244995
46000 1971.644043
47000 1994.526978
48000 2017.947998
49000 2041.961060
50000 2066.620117
51000 263.240997
52000 259.997986
53000 256.666992
54000 253.253998
55000 249.764999
56000 246.205994
57000 242.582993
58000 238.901993
59000 235.169006
60000 -609.200012
61000 -638.986023
62000 -668.968018
63000 -699.182007
64000 -729.664001
65000 -760.450012
66000 -791.575989
67000 -823.078003
68000 -854.992004
69000 -887.354004
70000 -920.200012
71000 2265.489990
72000 2332.820068
73000 2401.830078
74000 2472.459961
75000 2544.649902
76000 2618.340088
77000 2693.469971
78000 2769.979980
79000 2847.810059
80000 2926.899902
81000 -30821.759766
82000 -31601.679688
83000 -32391.119141
84000 -33190.441406
85000 -34000.000000
86000 -34820.160156
87000 -35651.281250
88000 -36493.718750
89000 -37347.839844
90000 -38214.000000
91000 -39092.558594
92000 -39983.878906
93000 -40888.320312
94000 -41806.238281
95000 -42738.000000
96000 -43683.960938
97000 -44644.480469
98000 -45619.921875
99000 -46610.640625
Until 40000, it looks ok, but after 41000 (t5 in your code) there is a sudden jump, so I think your equations are just wrong. Especially once the negative temperatures show up.

ahvz February 9, 2014 11:09
thank you very much for reply,

I couldnt get the correct equations through excell (it gives me the same as what I had before) thus, i decided to use a constant value (interval value) instead of equation and the solutions are converged.

when I implmenting another code (please see the second code) represent the properties for a material within the model. agian i have "converge problem" and it gives me wrong results. would you please check it?
regards,
Code:
/***********************************************************************
UDF example.c
UDF for specifying transient temperature profile boundary condition S
 ************************************************************************/
#include "udf.h"
#include "mem.h"
DEFINE_PROFILE(TempS48h_Profile, thread, position)   
{
real x[ND_ND];                                     
real y;
real t1=5000;
real t2=10000;
real t3=15000;
real t4=20000;
real t5=25000;
real t6=30000;
real t7=35000;
real t8=40000;
real t9=45000;
real t10=50000;
real t11=55000;
real t12=60000;
real t13=65000;
real t14=70000;
real t15=75000;
real t16=80000;
real t17=85000;
real t18=90000;
real t19=100000;
real t20=105000;
real t21=110000;
real t22=115000;
real t23=120000;
real t24=125000;
real t25=130000;
real t26=135000;
real t27=140000;
real t28=145000;
real t29=150000;
real t30=155000;
real t31=160000;
real t32=165000;
real t33=170000;
real theProfile;
face_t f;
begin_f_loop(f, thread);
 {
 F_CENTROID(x,f,thread);
 y = CURRENT_TIME;   
 
    if(y<=t1)
      {     
      theProfile=284;
      F_PROFILE(f, thread, position) =theProfile;   
      }
      else if (y<=t2 && y>t1)
      {
      theProfile=285.29; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t3 && y>t2)
      {
      theProfile=287.63; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t4 && y>t3)
      {
      theProfile=292.81; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t5 && y>t4)
      {
      theProfile=301.56; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t6 && y>t5)
      {
      theProfile=308.1; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t7 && y>t6)
      {
      theProfile=313.5; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t8 && y>t7)
      {
      theProfile=313.84; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t9 && y>t8)
      {
      theProfile=316.92; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t10 && y>t9)
      {
      theProfile=316.7; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t11 && y>t10)
      {
      theProfile=313.42; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t12 && y>t11)
      {
      theProfile=308.56; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t13 && y>t12)
      {
      theProfile=301.89; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t14 && y>t13)
      {
      theProfile=296.57; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t15 && y>t14)
      {
      theProfile=293.96; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t16 && y>t15)
      {
      theProfile=290.69; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t17 && y>t16)
      {
      theProfile=288.19; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t18 && y>t17)
      {
      theProfile=284.4; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t19 && y>t18)
      {     
      theProfile=284.14;
      F_PROFILE(f, thread, position) =theProfile;   
      }
      else if (y<=t20 && y>t19)
      {
      theProfile=285.66; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t21 && y>t20)
      {
      theProfile=288; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t22 && y>t21)
      {
      theProfile=294.43; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t23 && y>t22)
      {
      theProfile=302.8; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t24 && y>t23)
      {
      theProfile=309.24; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t25 && y>t24)
      {
      theProfile=314.52; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t26 && y>t25)
      {
      theProfile=317; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t27 && y>t26)
      {
      theProfile=316.4; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t28 && y>t27)
      {
      theProfile=312.67; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t29 && y>t28)
      {
      theProfile=307.45; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t30 && y>t29)
      {
      theProfile=300.74; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t31 && y>t30)
      {
      theProfile=296.03; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t32 && y>t31)
      {
      theProfile=293.46; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else if (y<=t33 && y>t32)
      {
      theProfile=290.2; 
      F_PROFILE(f, thread, position) =theProfile;
      }
      else
      {
      theProfile=284.5; 
      F_PROFILE(f, thread, position) =theProfile;
      }
 }
end_f_loop(f,thread)
}

/***********************************************************************
udfexample.c
UDF for specifying heat source heat sink
 ************************************************************************/


#include "udf.h"
 
DEFINE_SOURCE(energy_udf,c,t,dS,eqn)
{
real source;
real temp1=281;
real temp2=558;
real temp3=288;
real temp4=293;
real temp5=296;
real temp6=297;

if(N_TIME > 0)
{

if (C_T(c,t) > C_T_M1(c,t)) /* UDF for increasing temperature*/
{
if (C_T_M1(c,t) >= 280.140 && C_T(c,t) <= 300.20)

if(temp<=temp1)
      {     
      source=1.5;
      dS[eqn] =0;   
      }
else if (temp<=temp2 && temp>temp1)
      {     
      source=558;
      dS[eqn] =0;   
      }
else if (temp<=temp3 && temp>temp2)
      {     
      source=2583;
      dS[eqn] =0;   
      }
else if (temp<=temp4 && temp>temp3)
      {     
      source=9643;
      dS[eqn] =0;   
      }
else if (temp<=temp5 && temp>temp4)
      {     
      source=18395;
      dS[eqn] =0;   
      }
else if (temp<=temp6 && temp>temp5)
      {     
      source=22918;
      dS[eqn] =0;   
      }
else
      {     
      source=24477;
      dS[eqn] =0;   
      }     
}

else if (C_T(c,t) < C_T_M1(c,t)) /* UDF for decreasing temperature */
{
if (C_T_M1(c,t) <= 295.57 && C_T(c,t) >= 278.32)
{
if(temp<=temp1)
      {     
      source=23147;
      dS[eqn] =0;   
      }
else if (temp<=temp2 && temp>temp1)
      {     
      source=21972;
      dS[eqn] =0;   
      }
else if (temp<=temp3 && temp>temp2)
      {     
      source=19300;
      dS[eqn] =0;   
      }
else if (temp<=temp4 && temp>temp3)
      {     
      source=4765;
      dS[eqn] =0;   
      }
else if (temp<=temp5 && temp>temp4)
      {     
      source=12;
      dS[eqn] =0;   
      }
else if (temp<=temp6 && temp>temp5)
      {     
      source=4.7;
      dS[eqn] =0;   
      }
else
      {     
      source=1.2;
      dS[eqn] =0;   
      }   
}
}
}

return source;
}

pakk February 9, 2014 15:59
No, I am not going to do your work.
If you want to learn something, I am very willing to help you. If you just want me to fix your errors, I'll pass.

I have shown you how you can test your udf: compare what your udf should do to what your udf actually does. Now you do it. If you can not do this, do the best you can, and show your intermediate results here, and I'll help. But at least try...

ahvz February 10, 2014 14:35
thanks for your reply,

I used constant value (interval values) instead of using equations, in order to be sure of temperature profile for boundary condition. however, it takes a lot of time to do such a this but i have no other way. and finally, the result is acceptable of meaning.

in next step, I have face with another problem with strange result, when I implementing another code for my source term (pleas see the code) and can't find my problem. any help please?

regards,

Code:


/***********************************************************************
udfexample.c
UDF for specifying heat source heat sink
 ************************************************************************/


#include "udf.h"
 
DEFINE_SOURCE(energy_udf,c,t,dS,eqn)
{
real source;
real temp1=281;
real temp2=285;
real temp3=287;
real temp4=290;
real temp5=294;
real temp6=297;
real temp7=282;
real temp8=287;
real temp9=292;

if(N_TIME > 0)
{

if (C_T(c,t) > C_T_M1(c,t)) /* UDF for increasing temperature*/
{
if (C_T_M1(c,t) >= 280 && C_T(c,t) <= 300)

if(temp<=temp1)
      {     
      source=(65*pow(temp,1.))-18199;
      dS[eqn] =65;   
      }
else if (temp<=temp2 && temp>temp1)
      {     
      source=(193.75*pow(temp,1.))-54377.75;
      dS[eqn] =193.75;   
      }
else if (temp<=temp3 && temp>temp2)
      {     
      source=(2192*pow(temp,1.))-615111;
      dS[eqn] =2192;   
      }
else if (temp<=temp4 && temp>temp3)
      {     
      source=(488.34*pow(temp,1.))-138214.7;
      dS[eqn] =488.34;   
      }
else if (temp<=temp5 && temp>temp4)
      {     
      source=(1560.5*pow(temp,1.))-449143;
      dS[eqn] =1560.5;   
      }
else if (temp<=temp6 && temp>temp5)
      {     
      source=(4424.7*pow(temp,1.))-1291.208;
      dS[eqn] =4424.7;   
      }
else
      {     
      source=(498.34*pow(temp,1.))-125087;
      dS[eqn] =498.34;   
      }     
}

else if (C_T(c,t) < C_T_M1(c,t)) /* UDF for decreasing temperature */
{
if (C_T_M1(c,t) <= 295 && C_T(c,t) >= 278)
{
if(temp<=temp7)
      {     
      source=(-156*pow(temp,1.))+66516;
      dS[eqn] =-156;   
      }
else if (temp<=temp8 && temp>temp7)
      {     
      source=(-527.8*pow(temp,1.))+171363.6;
      dS[eqn] =0;   
      }
else if (temp<=temp9 && temp>temp8)
      {     
      source=(-2635.6*pow(temp,1.))+776302.2;
      dS[eqn] =-2635.6;   
      }
else
      {     
      source=(-2234*pow(temp,1.))+659035;
      dS[eqn] =-2234;   
      }   
}
}
}

return source;
}

pakk February 10, 2014 17:36
Quote:
Originally Posted by ahvz (Post 474328)
thanks for your reply,

I used constant value (interval values) instead of using equations, in order to be sure of temperature profile for boundary condition. however, it takes a lot of time to do such a this but i have no other way. and finally, the result is acceptable of meaning.

in next step, I have face with another problem with strange result, when I implementing another code for my source term (pleas see the code) and can't find my problem. any help please?
For the second time: No, I am not going to do your work.
If you want to learn something, I am very willing to help you. If you just want me to fix your errors, I'll pass.

I have shown you how you can test your udf: compare what your udf should do to what your udf actually does. Now you do it. If you can not do this, do the best you can, and show your intermediate results here, and I'll help. But at least try...

ahvz February 16, 2014 10:24
I think I Have sorted the problem was showed up by equations within the code (still not sure).

the problem was end point and start point of each equation indeed. because, in the last version that I submitted, there was non continuously (as I put randomly some points regarding just to check them).
so with changing the equation with power 3 to power 1 it was solved.


I faced with another problem, don't understand where is the problem.

until 19000sec the results are converged with time step size 30sec with 250iteration and 2880time steps.afterward, not convergence...

where is my mistake?

regards,


Code:
/***********************************************************************
UDF example.c
UDF for specifying transient temperature profile boundary condition
 ************************************************************************/
#include "udf.h"
#include "mem.h"
DEFINE_PROFILE(TempS_Profile, thread, position)   
{
real x[ND_ND];                                     
real y;
real t1=10000;
real t2=20000;
real t3=30000;
real t4=40000;
real t5=50000;
real t6=60000;
real t7=70000;
real t8=80000;

real theProfile;
face_t f;
begin_f_loop(f, thread);
 {
 F_CENTROID(x,f,thread);
 y = CURRENT_TIME;   
 
    if(y<=t1)
      {     
      theProfile=(0.0003*pow(y,1.))+283;
      begin_f_loop(f,thread)
            {
      F_PROFILE(f, thread, position) =theProfile;   
      }
            end_f_loop(f,thread)
      }
     
      else if (y<=t2 && y>t1)
      {
      theProfile=(0.0012*pow(y,1.))+274; 
      begin_f_loop(f,thread)
            {
      F_PROFILE(f, thread, position) =theProfile;
      }
            end_f_loop(f,thread)
      }
     
      else if (y<=t3 && y>t2)
      {
      theProfile=(0.0013*pow(y,1.))+272; 
      begin_f_loop(f,thread)
            {
      F_PROFILE(f, thread, position) =theProfile;
      }
            end_f_loop(f,thread)
      }
     
      else if (y<=t4 && y>t3)
      {
      theProfile=(0.0006*pow(y,1.))+293; 
      begin_f_loop(f,thread)
            {
      F_PROFILE(f, thread, position) =theProfile;
      }
            end_f_loop(f,thread)
      }
     
      else if (y<=t5 && y>t4)
      {
      theProfile=(-0.0006*pow(y,1.))+341; 
      begin_f_loop(f,thread)
            {
      F_PROFILE(f, thread, position) =theProfile;
      }
            end_f_loop(f,thread)
      }
     
      else if (y<=t6 && y>t5)
      {
      theProfile=(-0.0013*pow(y,1.))+376; 
      begin_f_loop(f,thread)
            {
      F_PROFILE(f, thread, position) =theProfile;
      }
            end_f_loop(f,thread)
      }
     
      else if (y<=t7 && y>t6)
      {
      theProfile=(-0.0006*pow(y,1.))+334; 
      begin_f_loop(f,thread)
            {
      F_PROFILE(f, thread, position) =theProfile;
      }
            end_f_loop(f,thread)
      }
     
      else if (y<=t8 && y>t7)
      {
      theProfile=(-0.0007*pow(y,1.))+341; 
      begin_f_loop(f,thread)
            {
      F_PROFILE(f, thread, position) =theProfile;
      }
            end_f_loop(f,thread)
      }
     
      else
      {
      theProfile=(-0.0003125*pow(y,1.))+310; 
      begin_f_loop(f,thread)
            {
      F_PROFILE(f, thread, position) =theProfile;
      }
            end_f_loop(f,thread)
      }
     
     
     
 }
end_f_loop(f,thread)
}




/***********************************************************************
udfexample.c
UDF for heat source heat sink
 ************************************************************************/


#include "udf.h"
 
DEFINE_SOURCE(energyPOW2,c,t,dS,eqn)
{
real source;

if(N_TIME > 0)
{

if (C_T(c,t) > C_T_M1(c,t))
{
if (C_T_M1(c,t) >= 287 && C_T(c,t) <= 300.20)
{
source = (101.6*pow(temp,2.))-(57581*pow(temp,1.))+8E+06;
dS[eqn] = (202.4*pow(temp,1.))-(57581);
}
}

else if (C_T(c,t) < C_T_M1(c,t))
{
if (C_T_M1(c,t) <= 295.57 && C_T(c,t) >= 278.32)
{
source =(133.25*pow(temp,2.))-(74998*pow(temp,1.))+1E+07;
dS[eqn] =(266.5*pow(temp,1.))-74998;
}
}
}
return source;
}


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