Self-Similar Multimode Bubble-Front Evolution of the Ablative Rayleigh-Taylor Instability in Two and Three Dimensions

The self-similar nonlinear evolution of the multimode ablative Rayleigh–Taylor instability is studied numerically in both two and three dimensions. It is shown that the nonlinear multimode bubble-front penetration follows the agt^2 scaling law with a dependent on the initial conditions and ablation velocity. The value of a is determined by the bubble‑competition theory, indicating that mass ablation reduces a with respect to its classical value for the same initial perturbation amplitude. It is also shown that ablation-driven vorticity accelerates the bubble velocity and prevents the transition from the bubble competition to the bubble-merger regime at large initial amplitudes, leading to higher values of a than in the classical case. These results are applied to explain the hydrodynamic-stability boundary observed in laser direct-drive implosion experiments.