[CamsDR]

Hello,


I have the following problem that I have to analyse in ANSYS Fluent. I have to simulate the transient temperature field due to natural convection in a vertical confined channel. I have been provided with a geometry and mesh and I have to choose a viscous model, implement the boundary conditions and set up the transient analysis. I was provided with very little information as you can see in the attached file. To choose a viscous model I have to determine the Rayleigh number. To determine the Rayleigh number I need the characteristic length. I thought that the characteristic length in this case would be the distance that the air travels so the length from bottom to top (which is 1 meter). However, when I asked my supervisor, he told me that the length refers to the phenomenon so the pipe in vertical direction. I don’t know what he means with this because the pipes have different diameters so I don’t know which one I have to choose then for the characteristic length. Can someone help me what the best approach is here to determine the Rayleigh number and choose the best viscous model?


I was also given a temperature profile of the pipes over 120 seconds. I want to implement this in the boundary conditions but I don’t know how. As I would prefer not to work with user defined functions, are there other options that I can use?



Thank you.