Rayleigh-Taylor Instability | Density Inversion

Heavy fluid above light fluid: interface fingers grow exponentially then form mushroom-cap plumes.

Atwood number A=(ρ₂-ρ₁)/(ρ₂+ρ₁) 0.50 Gravity g 9.8 Viscosity ν 0.002 Modes 4

σ = √(A·g·k) — viscous damping

RT instability: Rayleigh (1882), Taylor (1950). Growth rate σ=√(Agk) for inviscid; finger width ~ fastest-growing wavenumber. Mushroom caps form when nonlinear: heavy fluid plunges, light fluid rises in spikes. Key in ICF, supernovae, atmospheric convection.