Passive tracer transport in a 2D cavity flow · Poincaré sections reveal chaotic mixing
Re (top lid)400
Particles800
Steps/frame5
Trail length20
Lid-driven cavity flow produces recirculation regions. At finite Re, the streamfunction ψ satisfies ∇⁴ψ = 0 (Stokes) or the full NSE. Tracer advection ẋ=u(x,y), ẏ=v(x,y) can be chaotic due to horseshoe maps near separatrices.