[hitzhwan]

How to define a wall heat flux changing with flow time in udf？ Such as：
t<0.3, heat flux =10w/m^2;
t>=0.3,heat flux =1000w/m^2;

Other than udf, could we use an expression to solve this problem in fluent?

[AlexanderZ]

you can use profile or expression.
look for profile on this forum

[hitzhwan]

Originally Posted by AlexanderZ

you can use profile or expression.
look for profile on this forum

Would you please share me the codes for me? Thank you so much.

[siddhu23]

Originally Posted by hitzhwan

How to define a wall heat flux changing with flow time in udf？ Such as：
t<0.3, heat flux =10w/m^2;
t>=0.3,heat flux =1000w/m^2;

Other than udf, could we use an expression to solve this problem in fluent?

FYR:

#include "udf.h"

DEFINE_PROFILE(hf_change,thread,position) 
{
  face_t f;
  real time,heat_flux1,heat_flux2;
  heat_flux1 = 10;
  heat_flux2 = 100;
  time=CURRENT_TIME;
  begin_f_loop(f,thread)
  {
   
	if (time<0.3)
	{
	F_PROFILE(f,thread,position)=heat_flux1;
	}
        
	else if (time>=0.3)
	{
	F_PROFILE(f,thread,position)=heat_flux2;
	}
      	
   }
  end_f_loop(f,thread)
}

[hitzhwan]

Is this code right？ If yes， what is the difference？

#include "udf.h"
DEFINE_PROFILE(wall_heatflux, thread, position)
{
real t,q;
face_t f;
begin_f_loop(f, thread)
{
t=RP_Get_Real("flow-time");
{
if (t>0 && t<=0.50)
{
q=0;
}

else if (t>=0.5)
{
q=47300;
}

}
F_PROFILE(f,thread,position)=q;
}
end_f_loop(f,thread)
}

[siddhu23]

Originally Posted by hitzhwan

Is this code right？ If yes， what is the difference？

#include "udf.h"
DEFINE_PROFILE(wall_heatflux, thread, position)
{
real t,q;
face_t f;
begin_f_loop(f, thread)
{
t=RP_Get_Real("flow-time");
{
if (t>0 && t<=0.50)
{
q=0;
}

else if (t>=0.5)
{
q=47300;
}

}
F_PROFILE(f,thread,position)=q;
}
end_f_loop(f,thread)
}

#include "udf.h"
DEFINE_PROFILE(wall_heatflux,thread,position)
{
	real t,q;
	face_t f;
	t=RP_Get_Real("flow-time"); /* CURRENT_TIME & RP_Get_Real("flow-time") both return same value*/

	if ((t>0) && (t<=0.50))	/* both condition must closed with parentheses ((condition1) && (condition1) && ..... && (conditionN)) */
		{
		q=0;
		}
	else if (t>=0.5)
		{
		q=47300;
		}
	begin_f_loop(f,thread)
	{
        F_PROFILE(f,thread,position) = q;
	}
	end_f_loop(f,thread)
}

[AlexanderZ]

codes are almost same
but in your last code

t=RP_Get_Real("flow-time");

is inside face loop which is inefficient (code gets time on each face, even though, you can get it just once)
usually, you want to get time value from outside of the loop.

[siddhu23]

Originally Posted by AlexanderZ

codes are almost same
but in your last code

t=RP_Get_Real("flow-time");

is inside face loop which is inefficient (code gets time on each face, even though, you can get it just once)
usually, you want to get time value from outside of the loop.

Hi,

t=RP_Get_Real("flow-time"); each time the flow time will be updated even though the "t" outside of the loop.

[hitzhwan]

Originally Posted by AlexanderZ

codes are almost same
but in your last code

t=RP_Get_Real("flow-time");

is inside face loop which is inefficient (code gets time on each face, even though, you can get it just once)
usually, you want to get time value from outside of the loop.

In your giving code, why did you put the "begin_f_loop(f,thread)" after the if Statement？

#include "udf.h"
DEFINE_PROFILE(wall_heatflux,thread,position)
{
real t,q;
face_t f;
t=RP_Get_Real("flow-time"); /* CURRENT_TIME & RP_Get_Real("flow-time") both return same value*/

if ((t>0) && (t<=0.50)) /* both condition must closed with parentheses ((condition1) && (condition1) && ..... && (conditionN)) */
{
q=0;
}
else if (t>=0.5)
{
q=47300;
}
begin_f_loop(f,thread)
{
F_PROFILE(f,thread,position) = q;
}
end_f_loop(f,thread)
}

[hitzhwan]

Originally Posted by AlexanderZ

codes are almost same
but in your last code

t=RP_Get_Real("flow-time");

is inside face loop which is inefficient (code gets time on each face, even though, you can get it just once)
usually, you want to get time value from outside of the loop.

You mean the “time=CURRENT_TIME;” and “t=RP_Get_Real("flow-time")” have the same function？

[AlexanderZ]

read Ansys Fluent Customization manual carefully,
it has good examples inside
all your questions as of now are covered there

[siddhu23]

Originally Posted by hitzhwan

You mean the “time=CURRENT_TIME;” and “t=RP_Get_Real("flow-time")” have the same function？

Yes.
Refer the link below. For more detail.

https://www.afs.enea.it/project/nept...df/node112.htm

[hitzhwan]

Originally Posted by AlexanderZ

read Ansys Fluent Customization manual carefully,
it has good examples inside
all your questions as of now are covered there

Hi， because I am not familar with C language，it is hard for me to understand, do you have any better material (such as vedio)to learn it , thank you.