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-   -   Time-Varying Temperature Profiles (http://www.cfd-online.com/Forums/ansys/80825-time-varying-temperature-profiles.html)

shepardsp October 7, 2010 16:55

Time-Varying Temperature Profiles
 
Hi,

Is there a way to enter time-varying profiles for external wall boundary conditions in Fluent? Specifically, I would like to vary the free stream temperature and external radation temperature as functions of time for an unsteady flow calculation. Reading through the documentation on profiles, it sounds like you can specify spacial profiles but I have not found any literature on time-varying profiles. I attempted to read in a profile but it gave me errors, and the help documentation is limited. It's not clear what variable names to assign to the free stream temperature and radiation temperature, and it also gives me an error saying the number of points entered don't match the number specified at the top (I believe this is because you need to enter x/y coords for the 'point' option, but I want time varying, not spacial varying).

There is a drop-down menu under the wall boundary conditions window for each of the free stream temperature and external radiation temperature profiles, but each is set to constant and there are no other options. However since there are drop-down arrows, this leads me to believe that there is a way to read in a time-varying profile, unless this is just there for reading in spacial-varying profiles.

Thanks for the help!
Steve

NormalVector October 14, 2010 16:33

Are you familiar with the tutorial for Fluent V6? One of the tutorials uses a time varying pressure boundary condition. I am also trying to tackle similar problem: heat transfer with a time dependent boundary condition. I'm trying to decipher the UDF that goes with the tutorial but I don't know C. = /

Anyone else have ideas?

omair11 October 16, 2010 10:24

You need to know a little bit of C to use this.
Just copy and paste the given udf code in a text file and save it with a .c extension. in this file x1[0] is the x coordinate, x1[1] is the y coordinate and if your case is 3d, x1[2] is z coordinate. tima is the time.

just enter a mathematical expression for your profile and vala! time varying profiles.

==========================================
#include "udf.h"
DEFINE_PROFILE(profilename, thread, nv)
{
face_t f;
real x1[ND_ND];
real tima;
begin_f_loop (f,thread)
{

F_CENTROID(x1,f,thread);
tima=CURRENT_TIME;
F_PROFILE(f,thread,nv) =!!!!--enter expression here as a function of space and time------!!!!!
}
end_f_loop (f,thread)

}

NormalVector October 17, 2010 14:36

Thanks for the code! If you just want a boundary condition as a function of time only, just leave out the spacial coordinates?


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