code_saturne User's Forum

Hello,

I am trying to simulate natural convection around some heated components in a closed 1m3 volume. The problem I have is temperature divergence. The initial and ambient temperature of the surrounding air is 70° and the components are at 125° and 170°. But at the end of my calculation there are a small number of elements located in the rising air that are below 70°, which is not physical.

I see two potential sources of this problem:
1) I have used too larger time step (0.5s)
2) The Linear production k-epsilon turbulence model is not appropriate for my mesh, hence warning 'mesh too refined at the wall'

Any advice would be greatly appreciated.

Many thanks,
Nico

Hello.

For natural convection cases SST turbulence model is usually used, k-epsilon is definitely not a good choice for this. Your mesh should have a boundary prism layer at the heated surface with Y+ around 1.0 (see, for example, Y+ calculator at cfd-online.com, let the freestream velocity be 1.0 m/s, then verify in ParaView).