[Zhudasch]

Hi everybody. I'm now confused about how to do a grid sensitivity studie in a simulation that includes high-speed free jet (not supersonic) and natural convection.

The case is shown in the picture. To make the things easier I took just a pipe to do the study. The case goes like this: first the pipe will be heated to a stable condition with hot air (700 °C) . The hot air will be exhausted by an air exhaust fan. The maximum velocity in this period is about 140m/s. Then the hot air system will be shut down and the pipe will be cooled down because of natural convection.

I think there are at least 6 parameters I need to study:
1. Which kind of element I use. Polyhedral or Trimmed Cell.
2. The size of Element inside the pipe in both options
3. The configuration of prism layer (the thickness of 1st layer, the total thickness)
4. The refinement of the free jet and natural convection
5. The size of the element on the wall of the laboratory (about 6m*4m*3m).
6. The size of the element on the solid side. The influence on heat transfer.

I don't know how to do such a study with so many variables. Can anyone give me a hint? Like which one I should study first and then use the knowledge to study the second?

Thanks a lot.