[hitzhwan]

Can any tell me which is right for the below codes？

The first one：


#include "udf.h"



DEFINE_PROFILE(hf_change,thread,position)
{
face_t f;
real time,heat_flux1,heat_flux2;
heat_flux1 = 0;
heat_flux2 = 500;
time=CURRENT_TIME;
begin_f_loop(f,thread)
{

if (time<0.0001)
{
F_PROFILE(f,thread,position)=heat_flux1;
}

else if (time>=0.0001)
{
F_PROFILE(f,thread,position)=heat_flux2;
}

}
end_f_loop(f,thread)
}



The second one：

#include "udf.h"



DEFINE_PROFILE(hf_change,thread,position)
{
face_t f;
real time,heat_flux1,heat_flux2;
heat_flux1 = 0;
heat_flux2 = 500;

begin_f_loop(f,thread)
{
time=CURRENT_TIME;
if (time<0.0001)
{
F_PROFILE(f,thread,position)=heat_flux1;
}

else if (time>=0.0001)
{
F_PROFILE(f,thread,position)=heat_flux2;
}

}
end_f_loop(f,thread)
}

[AlexanderZ]

first one is better, cause you will execute macro CURRENT_TIME once (outside of the loop). So in case you have few hundred millions of finite cells in model, you will feel the effect.
But both wold give same result.

[pakk]

It's even possible that the compiler is smart enough to put it out of the loop, and give you identical compiled code.

So I would say: use the one you expect to still understand two years from now.

My version would be like this:

#include "udf.h"

DEFINE_PROFILE(hf_change,thread,position)
{
face_t f;
const real heat_flux1 = 0;
const real heat_flux2 = 500;
const real switch time = 0.0001;
const real time = CURRENT_TIME;
const real hf = time<switch_time?heat_flux1:heat_flux2;
begin_f_loop(f,thread)
{
F_PROFILE(f,thread,position)=hf;
}
end_f_loop(f,thread)
}

If you think your version is easier to understand, use yours.

[hitzhwan]

Originally Posted by AlexanderZ

first one is better, cause you will execute macro CURRENT_TIME once (outside of the loop). So in case you have few hundred millions of finite cells in model, you will feel the effect.
But both wold give same result.

Thank you so much for your help.
Sorry, the first one is better,you mean the two codes can achieve the same function, there is no wrong in the code 2?

But I have question, if the macro CURRENT_TIME once is put outside of the loop, I think the code will only execute only once, is that right?

I do not understand your meaning of "So in case you have few hundred millions of finite cells in model, you will feel the effect.
But both wold give same result."


In the end, I use both these two codes, they do not work in my run, what is the reason?

[hitzhwan]

Originally Posted by pakk

It's even possible that the compiler is smart enough to put it out of the loop, and give you identical compiled code.

So I would say: use the one you expect to still understand two years from now.

My version would be like this:

#include "udf.h"

DEFINE_PROFILE(hf_change,thread,position)
{
face_t f;
const real heat_flux1 = 0;
const real heat_flux2 = 500;
const real switch time = 0.0001;
const real time = CURRENT_TIME;
const real hf = time<switch_time?heat_flux1:heat_flux2;
begin_f_loop(f,thread)
{
F_PROFILE(f,thread,position)=hf;
}
end_f_loop(f,thread)
}

If you think your version is easier to understand, use yours.

Hi,pakk, thank you for your help, I have a question ,is there any wrong with the below code, there is a "?" here, is that right?

const real hf = time<switch_time?heat_flux1:heat_flux2;


When I use your code to compile, it gives the following error, what is the reason?

************************************************** **************************
************************************************** **************************
** WARNING: Automatically switched to run in parallel -t1 mode. **
** Detected non-parallelized UDF usage, enabling parallel usage. **
** If you encounter any issues, please re-run with -t0 flag. **
************************************************** **************************
************************************************** **************************Creating user_nt.udf file for 2ddp_host ...
(system "copy "D:\PROGRA~1\ANSYSI~1\v190\fluent"\fluent19.0.0\sr c\udf\makefile_nt.udf "libudf\win64\2ddp_host\makefile" ")
ÒѸ´ÖÆ 1 ¸öÎļþ¡£
(chdir "libudf")(chdir "win64\2ddp_host")# Generating ud_io1.h
wallheat.c
..\..\src\wallheat.c(8) : error C2143: Óï·¨´íÎó : ȱÉÙ¡°;¡±(ÔÚ¡°switch¡±µÄÇ°Ãæ)
..\..\src\wallheat.c(8) : error C2059: Óï·¨´íÎó:¡°¿ÕÉùÃ÷¡±
..\..\src\wallheat.c(8) : error C2061: Óï·¨´íÎó: ±êʶ·û¡°time¡±
..\..\src\wallheat.c(9) : error C2143: Óï·¨´íÎó : ȱÉÙ¡°;¡±(ÔÚ¡°const¡±µÄÇ°Ãæ)
..\..\src\wallheat.c(10) : error C2143: Óï·¨´íÎó : ȱÉÙ¡°;¡±(ÔÚ¡°ÀàÐÍ¡±µÄÇ°Ãæ)
..\..\src\wallheat.c(13) : error C2065: ¡°hf¡±: δÉùÃ÷µÄ±êʶ·û

************************************************** **************************
************************************************** **************************
** WARNING: Automatically switched to run in parallel -t1 mode. **
** Detected non-parallelized UDF usage, enabling parallel usage. **
** If you encounter any issues, please re-run with -t0 flag. **
************************************************** **************************
************************************************** **************************Creating user_nt.udf file for 2ddp_node ...
(system "copy "D:\PROGRA~1\ANSYSI~1\v190\fluent"\fluent19.0.0\sr c\udf\makefile_nt.udf "libudf\win64\2ddp_node\makefile" ")
ÒѸ´ÖÆ 1 ¸öÎļþ¡£
(chdir "libudf")(chdir "win64\2ddp_node")# Generating ud_io1.h
wallheat.c
..\..\src\wallheat.c(8) : error C2143: Óï·¨´íÎó : ȱÉÙ¡°;¡±(ÔÚ¡°switch¡±µÄÇ°Ãæ)
..\..\src\wallheat.c(8) : error C2059: Óï·¨´íÎó:¡°¿ÕÉùÃ÷¡±
..\..\src\wallheat.c(8) : error C2061: Óï·¨´íÎó: ±êʶ·û¡°time¡±
..\..\src\wallheat.c(9) : error C2143: Óï·¨´íÎó : ȱÉÙ¡°;¡±(ÔÚ¡°const¡±µÄÇ°Ãæ)
..\..\src\wallheat.c(10) : error C2143: Óï·¨´íÎó : ȱÉÙ¡°;¡±(ÔÚ¡°ÀàÐÍ¡±µÄÇ°Ãæ)
..\..\src\wallheat.c(13) : error C2065: ¡°hf¡±: δÉùÃ÷µÄ±êʶ·û

Done.

[pakk]

There should be an underscore between switch and time, sorry. Not in the line you quote, but in line 8.

But if you don't understand my code:don't use it. If you don't understand it, you can not maintain it.

[hitzhwan]

Originally Posted by pakk

There should be an underscore between switch and time, sorry. Not in the line you quote, but in line 8.

But if you don't understand my code:don't use it. If you don't understand it, you can not maintain it.

Thank you ，Pakk， you are right , after I add a underscore, it has no error. But it still cannot change the heat flux. I think the code is not too difficult to understand, does there has other thing should I do before I run? Would you please tell me how to process it, thank you so much.

[pakk]

How did you investigate that the heat Flux did not change?

[hitzhwan]

Originally Posted by pakk

How did you investigate that the heat Flux did not change?

I monitor the heat flux of the wall and plot it in the console.

[pakk]

Change heatflux1 to 1000, just to see if you see a difference.

[hitzhwan]

Originally Posted by pakk

Change heatflux1 to 1000, just to see if you see a difference.

There is no difference， the heat flux is still 0， it shows the codes does not work.

[pakk]

No, it shows that
- the code is not used (did you really apply it to the BC? And really this version?)
- OR your method to get heat flux is wrong. Do you see temperatures changing?

[hitzhwan]

Originally Posted by pakk

No, it shows that
- the code is not used (did you really apply it to the BC? And really this version?)
- OR your method to get heat flux is wrong. Do you see temperatures changing?

Yes，the code is applied on the BC，I use the compiled method， and I Hook it by the Drop-down menu. Can you use it in your computer?

[pakk]

No, I don't have Fluent on my pc.

[AlexanderZ]

everything works well.
and monitor works well either:
in surface report definition window
area-weight average -> wall fluxes -> total surface heat flux

[aregdgshj]

first code is better

[hitzhwan]

Originally Posted by AlexanderZ

everything works well.
and monitor works well either:
in surface report definition window
area-weight average -> wall fluxes -> total surface heat flux

Have you run it in your pc? which code do you use?

[AlexanderZ]

I've used code of Pakk, but all of them works.
1. compile code
2. load compiled library
3. select any wall -> thermal tab -> heat flux -> select udf function instead of constant

run transient simulation

[hitzhwan]

Originally Posted by AlexanderZ

I've used code of Pakk, but all of them works.
1. compile code
2. load compiled library
3. select any wall -> thermal tab -> heat flux -> select udf function instead of constant

run transient simulation

You mean the below code you load work? Why I have some errors when I load it by the same process, what fluent edition do you use? Would you please send me your case and udf to me, I want to try more, thank you so much .
#include "udf.h"

DEFINE_PROFILE(hf_change,thread,position)
{
face_t f;
const real heat_flux1 = 0;
const real heat_flux2 = 500;
const real switch time = 0.0001;
const real time = CURRENT_TIME;
const real hf = time<switch_time?heat_flux1:heat_flux2;
begin_f_loop(f,thread)
{
F_PROFILE(f,thread,position)=hf;
}
end_f_loop(f,thread)
}

[AlexanderZ]

Unfortunately, I'm not able to send you any files.

This is not the problem of version, code is simple and should work in any version.

I recommend you to make new test simple geometry:
rectangular, make it solid, not fluid
make new source file (with other name) and compile it again
load and apply UDF, run transient simulation

most likely, you didn't compile the code