Dynamics of chaotic Rayleigh-Taylor bubble fronts

Mechanisms governing the general evolution of chaotic Rayleigh-Taylor bubble fronts are explored, including merger, competition and their interaction. Evolutions of characteristic quantities, i.e., the diameter of dominant bubble D and the height of bubble mixing zone h, are formulated and validated. The D expands self-similarly with universal aspect ratio D/h ≈ (1+A)/4. In contrast, the h grows quadratically with growth coefficient α≡ h/(Agt²) depending on mechanism:α=α_m ≈1/36 for pure merger, α=α_c ≈[2Φ/ln(2η₀)]² for pure competition, and α=max{α_m,α_c} when two mechanisms co-work, where A,η₀ and Φ denote dimensionless density ratio, initial perturbation amplitude, and linear-growth-rate ratio of actual fluid to ideal fluid, respectively.