Learning Forum

[sleontsi]

Hi all,

First post, so apologies for any ignorance in advance.

I'm trying to implement a variable heat load of an object, generated as a function of the object's temperature. I figure out that I can't do it with a steady-state or transient thermal simulation, as in the formula that I can write as load, the object's temperature can't be an input. So, I guess the "Fluid Flow (Fluent)" is the only option? Do I have to write my own UDF script and load it? Is there a template somewhere that I can use?

Thanks a lot!

[Rob]

What are you trying to model? 

[sleontsi]

At this point I'm simulation a pipe and two blocks of silicon. The first block is generating constant heat and I'd like to model the heat generation of the second block, as a function of its temperature.

 

Thanks for the reply!!

[Rob]

You can probably use an expression (Fluent 2019) to link temperature to heat flux (source term) but adding heat will add to the temperature so may not be overly stable. 

[sleontsi]

Thanks for the reply! I'm not sure though how the structure of the UDF works.. How the temperature calculated by ANSYS is linked with the variables in ANSYS. Is there an example that you can point me to?

 

Thanks again!!

[Rob]

There are examples of various codes in the UDF Manual: look in the section on Source terms. There may not be a temperature dependent function, but behaviour is the same as for position etc, you just use a different macro. 

[sleontsi]

thanks a lot for the hint!!

[Rob]

You're welcome. When you figure it out please post the code for others to use: feel free to hide the actual equation just leave enough that it's clear how the flux and temperature are linked. 

[sleontsi]

So, I used a UDF and the methods DEFINE_PROFILE, C_CENTROID and F_PROFILE. Each cell's temperature can be derived by C_T(c,t) and applied with a formula based on F_PROFILE(c,t,i).