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PARAMETERS
τ (relaxation): —
ν (viscosity): —
Steps: 0
D2Q9 Lattice Boltzmann propagates distribution functions f_i along 9 discrete velocities, then relaxes toward local equilibrium (BGK).
f_i → f_i + (f_i^eq − f_i)/τ. The macroscopic density ρ = Σf_i and velocity u = Σf_i·e_i/ρ emerge from the mesoscale.
Flow past a cylinder creates the famous Kármán vortex street at moderate Reynolds numbers — periodic, symmetric shedding.