[Sorabh]

Hello,
I am solving a problem where a face will receive a heat flux for 2 seconds and then, it will be at a constant temperature for the rest of the time.

Something like this:


How do I do this?
Thanks...

EDIT: I tried something like this:

DEFINE_PROFILE(heat_flux,thread,position)   //The UDF profile will have the name “heat_flux” 
{ 
  face_t f; //Define face variable 
  double x[ND_ND],time;  
  time=RP_Get_Real("flow-time"); //Acquire time from FLUENT solver 
  begin_f_loop(f,thread)  //Loop through all relevant boundary faces 
  { 
    if (time < 6e-5)
		F_PROFILE(f,thread,position)= IO; //IO = 4e9
	else{
		F_PROFILE(f,thread,position) = 0;
		F_T(f,thread) = 110;
	}
    end_f_loop(f,thread)
  } 
}

However, the results were not what was excepted. I excepted the temperature in that particular area to be 110 K, but on reaching the steady state, the temperature is around 410 K.

What am I doing wrong?

[pakk]

First of all: your wall can be adiabatic (no heat flux) or isothermal (specified temperature), not both. You have to choose which one you want. I can't tell you that, both are possible, it depends on the problem that you are trying to solve.

Secondly: you say it happens after two seconds, but in the code it is 6e-5 seconds.



If you want it to be adiabatic after some time: remove the line "F_T(f,thread) = 110;".
If you want it to be isothermal after some time: do the simulation until that time, and then change the type of boundary condition (by hand of by scheme script).




Finally: unless you have additional heat sources that you are not describing, it makes no sense that your steady state temperature is anything else than 110 K, since you have one wall at 110 K and no other fixed temperatures. So you probably have something in your simulation that you are not describing here (possibly because you are unaware of it), or your simulation did not converge and you are looking at a diverged solution.

[Sorabh]

Oh I was about to edit the original post, saw my mistake therein.

And your suggestion worked out. I got what I was looking for, Thanks!