D2Q9 LBM simulation — draw walls, watch Kármán vortex street form
Click/drag on canvas to draw solid walls. Watch vortices shed behind obstacles.
The Lattice Boltzmann Method simulates fluid by evolving discrete velocity distributions on a grid.
D2Q9: 9 velocity directions per cell. BGK collision: f → f + (f_eq - f)/τ. τ = 3ν + 0.5.
At high Re: Kármán vortex street — alternating vortices shed periodically. Re = UL/ν, shedding frequency: St = fL/U ≈ 0.21.