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Growth of the single-fluid single-mode Rayleigh-Taylor instability (RTI) isrevisited in 2D and 3D using fully compressible high-resolution simulations. Weconduct a systematic analysis of the effects of perturbation Reynolds number($Re_p$) and Atwood number ($A$) on RTI's late-time growth. Contrary to thecommon belief that single-mode RTI reaches a terminal bubble velocity, we showthat the bubble re-accelerates when $Re_p$ is sufficiently large, consistentwith [Ramaparabhu et al. 2006, Wei and Livescu 2012]. However, unlike in[Ramaparabhu et al. 2006], we find that for a sufficiently high $Re_p$, thebubble's late-time acceleration is persistent and does not vanish. Analysis ofvorticity dynamics shows a clear correlation between vortices inside the bubbleand re-acceleration. Due to symmetry around the bubble and spike (vertical)axes, the self-propagation velocity of vortices points in the verticaldirection. If viscosity is sufficiently small, the vortices persist long enoughto enter the bubble tip and accelerate the bubble [Wei and Livescu 2012]. Asimilar effect has also been observed in ablative RTI [Betti and Sanz 2006]. Asthe spike growth increases relative to that of the bubble at higher $A$,vorticity production shifts downward, away from the centerline and toward thespike tip. We modify the Betti-Sanz model for bubble velocity by introducing avorticity efficiency factor $\eta=0.45$ to accurately account forre-acceleration caused by vorticity in the bubble tip. It had been previouslysuggested that vorticity generation and the associated bubble re-accelerationare suppressed at high $A$. However, we present evidence that if the large$Re_p$ limit is taken first, bubble re-acceleration is still possible. Ourresults also show that re-acceleration is much easier to occur in 3D than 2D,requiring smaller $Re_p$ thresholds.

Revisiting the Late-Time Growth of Single-mode Rayleigh-Taylor Instability and the Role of Vorticity