Lattice Boltzmann method for natural convection
 

Hi all,

Currently I am developing a hybrid melting/solidification model in Python using the Lattice Boltzmann method (LBM) for the flow and a finite difference scheme for temperature. The basic model without melting is almost finished, except for one error that I narrowed down to the flow part. For this part bounce-back boundary conditions are used. I checked everything in this code, but cannot seem to find anything out of order. The velocity should form a vortex, however the velocity in the x-direction is an order of magnitude too low.
I added diagrams of the velocity, density and temperature in a cavity with a hot and cold wall and adiabatic BCs at the top and bottom. The flow is developed.

Does somebody know what might go wrong by looking at the results? I know it is a long shot, but it will help me a great deal if it works. :) Thanks!

Regards,
Jesper

https://i.postimg.cc/CdrJgck5/arrowplot-time20.png

https://i.postimg.cc/XXYxmRZt/heatmap-rho-time20.png

https://i.postimg.cc/QKCb77Gj/heatmap-T-time20.png