On the effects of variable deceleration periods on Rayleigh-Taylor instability with multiple acceleration reversals*

We will discuss results from our numerical simulations to study the effects of time-varying stabilizing deceleration periods on the Rayleigh-Taylor instability (RTI) when subjected to multiple acceleration reversals at different Atwood numbers (0.05 and 0.5). A massively parallel implicit large eddy simulation code, MOBILE was used to simulate the multiple reversal (accel-decel-accel or ADA) cases; the results were compared with a single reversal (accel-decel or AD) and no reversal (classical constant gravity) case.  During the deceleration period, evidence of internal wave-like patterns can be observed inside the mixing layer. The re-acceleration point was varied based on the phase of the internal waves generated in the AD cases. This allowed for a series of ADA cases with varying deceleration periods that highlight possible effects of the wavelike motion during the deceleration phase on the late time growth of the instability after re-acceleration. To better characterize and compare instability growth after re-acceleration, multiple parameters were analyzed, including the integral mixing width, growth rates, and anisotropic tensor for the kinetic energy.