Reply To: Stability of 3D thermal LBM model
3D simulations being easier to be instable sounds resonable. You have more degrees of freedom, more calculations that could potentially intodruce numerical errors. Also, do not forget that turbulence in 2D is a completely different phenomenon than in 3D!
Above Ra>=1e7 these simulations transition to turbulent natural convection and eddies will arise. Are you using a turbulence model for your simulations or are you wanting to resolve all structures? If no turbulence model is applied, check your resolution. It should be high enough to resolve the boundary layer that develops close to the heated and cooled walls. You can find some more info in e.g. https://doi.org/10.1016/j.camwa.2018.08.018.