[phanikumar]

Hi,

Could anyone please tell me how to define the temperature of the wall in fluent which depends on time. I have approched in away but it shows an error such as "invalid lvalue in assignment.". Please resolve the error in the following program or please let me know how to program this particular scenario as I'm very bad at programming.


Program:

#include "udf.h"

DEFINE_PROFILE(temperature, t, i)
{
real the_current_time;
face_t f;

the_current_time = CURRENT_TIME;

if ((the_current_time>=0) && (the_current_time<=3600))
{
temperature=20;
}
if ((the_current_time>3600) && (the_current_time<=7200))
{
temperature=19;
}
if ((the_current_time>7200) && (the_current_time<=10800))
{
temperature=18;
}
if ((the_current_time>10800) && (the_current_time<=14400))
{
temperature=17;
}
if ((the_current_time>14400) && (the_current_time<=18000))
{
temperature=16;
}
if ((the_current_time>18000) && (the_current_time<=21600))
{
temperature=21;
}
if ((the_current_time>21600) && (the_current_time<=25200))
{
temperature=31;
}
if ((the_current_time>25200) && (the_current_time<=28800))
{
temperature=43;
}
if ((the_current_time>28800) && (the_current_time<=32400))
{
temperature=56;
}
if ((the_current_time>32400) && (the_current_time<=36000))
{
temperature=66;
}
if ((the_current_time>36000) && (the_current_time<=39600))
{
temperature=70;
}
if ((the_current_time>39600) && (the_current_time<=43200))
{
temperature=70;
}
if ((the_current_time>43200) && (the_current_time<=46800))
{
temperature=75;
}
if ((the_current_time>46800) && (the_current_time<=50400))
{
temperature=72;
}
if ((the_current_time>50400) && (the_current_time<=54000))
{
temperature=72;
}
if ((the_current_time>54000) && (the_current_time<=57600))
{
temperature=63;
}
if ((the_current_time>57600) && (the_current_time<=61200))
{
temperature=55;
}
if ((the_current_time>61200) && (the_current_time<=64800))
{
temperature=47;
}
if ((the_current_time>64800) && (the_current_time<=68400))
{
temperature=39;
}
if ((the_current_time>68400) && (the_current_time<=72000))
{
temperature=29;
}
if ((the_current_time>72000) && (the_current_time<=75600))
{
temperature=24;
}
if ((the_current_time>75600) && (the_current_time<=79200))
{
temperature=22;
}
if ((the_current_time>79200) && (the_current_time<=82800))
{
temperature=21;
}
if ((the_current_time>82800) && (the_current_time<=86400))
{
temperature=19;
}

begin_f_loop(f,t)
{
F_PROFILE(f,t,i) = temperature;
}
end_f_loop(f,t)
}

[KaLium]

You use "temperature" as both variable and UDF-name. (And you do not define the variable)

[KaLium]

I would make something like:

#include "udf.h"

DEFINE_PROFILE(temperature, t, i)
{
real the_current_time, Temp;
face_t f;

the_current_time = CURRENT_TIME;

if ((the_current_time>=0) && (the_current_time<=3600))
{
Temp=20.0;
}
if ((the_current_time>3600) && (the_current_time<=7200))
{
Temp=19.0;
}

...

}

[phanikumar]

Hi KaLium,

Thank you verymuch. It's working perfectly.