Heavy fluid above light fluid under gravity · Finger formation · Growth rate σ = √(Ag·k)
Atwood # A0.50
Gravity g2.0
Perturbation k3
Viscosity ν0.10
Noise0.10
Growth rate σ = — | time = —
Rayleigh-Taylor instability: dense fluid ρ₁ above lighter ρ₂ in gravity g. Atwood number A=(ρ₁−ρ₂)/(ρ₁+ρ₂). Linear growth rate σ=√(Agk) for wavenumber k (surface tension stabilizes small scales). Nonlinear: heavy fluid forms "spikes" falling down, light fluid forms "bubbles" rising up.