LBM in your pocket
A lid-driven cavity, solved by particles that only collide and stream. No pressure equation, no mesh. The whole solver is on the right (… lines).
lid moving right →
The entire solver
Try it: drag Re up and watch the corner eddies grow, then keep going until it breaks. That limit is τ → ½, which is where research on collision models begins. Research codes add curved walls, multiphase flow, GPUs and much more.