Dynamical balances in transitional and self-similar Rayleigh-Taylor mixing layers

We study the dynamical balances in the pre-virtual origin and the self-similar Rayleigh-Taylor mixing layer to contrast the pre-transition and the self-similar layer. We employ two narrow-band initial conditions for the density interface, with low and high non-dimensional amplitudes or equivalently the interface slope. A large interface slope skips the linear growth phase and meaningfully reduces the virtual origin as the perturbations take a rapid nonlinear and alternate speedier route to transition; via ballistic ejecta as opposed to bubble and spikes. In this regime, the early growth is linear in nature as opposed to the early quadratic growth prevalent in the conventional bubble-spike growth picture. This pushes forward the virtual origin for the self-similar development for an identical perturbation length with a smaller interface slope. We show that the virtual origin of the self-similar growth is fundamentally connected to the transition metrics. With the two transition routes, we investigate how the memory of the perturbations considered in the study fades past the virtual origin and if any aspects persist in the late time large-scale structures. Self-similar mass flux dynamics in the variable-density turbulence is also contrasted with the dynamics in Boussinesq turbulence.