Navier-Stokes Vorticity

2D incompressible Navier-Stokes in vorticity-streamfunction form: ∂ω/∂t + u·∇ω = ν∇²ω. The streamfunction ψ satisfies ∇²ψ = −ω (Poisson), with u = ∂ψ/∂y, v = −∂ψ/∂x.