A heavy fluid sits atop a lighter fluid. Small perturbations at the interface grow exponentially (RT instability), forming characteristic "mushroom" plumes and interpenetrating spikes.
Parameters
t = 0.00
Atwood number A=(ρ₂−ρ₁)/(ρ₂+ρ₁) Growth rate: σ = √(Agk) for wavenumber k
Simulated with density-weighted vortex sheet method