Numerical Investigation of the Rayleigh-Taylor Instability Under Sharp and Sinusoidal Acceleration Switches

We study the dynamic properties of an interfacial flow between heavy and light incompressible fluids, which becomes Rayleigh-Taylor (RT) unstable when the system is subjected to an external acceleration field in the opposite direction of the density gradient. We perform implicit large eddy simulations (ILES) of RT instability under time-dependent sharp and smooth acceleration reversals. The majority of RT instability studies under variable acceleration have used a series of step functions. However, it is conjectured that a sinusoidal profile, which allows a smoother transition from acceleration to deceleration or vice versa, would better represent these transitions in real applications. We examine the performance of the length scale, Z(t), computed by integrating the time-variable acceleration over time in capturing RTI dynamics. In addition, we will discuss the time evolution of various parameters, including mass flux, Reynolds stress anisotropy tensor, and molecular mixing, to further discuss RTI mixing dynamics.