Problem with Simple Free Covection Model

[Anonymous]

Hello All,

I'm a new user of the software.  As validation I'm trying to compare calulated and test results againts the CF solution.

The model is a simple simulation of a heated cylinder freely convecting and radiating into an air environment.  My model meshes and runs without problems but no heat transfer is occuring and the simulation ends due to the convergence monitor detecting flat lines.

A check using the results planes does indeed indicate that no heat is being genereated/transfered despite having set up a resistive element and supplied it with a power value.

I think I am missing something simple.  Any help would be appreciated.

Regards,

Scott

[Royce_adsk · Accepted solution]

A few quick comments regarding your model

1) Only have pressure on the top and bottom surfaces
2) If you are new to the software don't include radiation. When you do include radiation add temperature boundary conditions to the 4 vertical walls in the external air domain.
3) Initial Conditions (ICs) typically are not needed for a steady state solution.
4) The 'Biggest' problem is your unit system. Your model is 634 meters tall. Adjust your units and I bet your model will be more successful!

Cheers,
Royce

[Anonymous]

Royce,

4) The 'Biggest' problem is your unit system. Your model is 634 meters tall. Adjust your units and I bet your model will be more successful!

Bingo, it should have been millimeters not meters,  thanks for the help.

Because my convection coefficients are so low, radiation is a significant component.  I ran once without radiation as you suggested and saw a 5 degree delta vs my test and calculations.  I reran the simulation with radiation on and my external surface temps are now within 1C of my other values.  Very impressive piece of code.

Again thanks for the swift response.

[Royce_adsk]

Awesome! Glad I could help out. And impressive correlation 🙂