Recovery towards self-similarity in Rayleigh-Taylor instability under stepwise and sinusoidal acceleration reversals

Area of Science:

• Fluid Dynamics
• Plasma Physics

Background:

• Rayleigh-Taylor instability is critical in natural phenomena (supernovae) and engineering (fusion energy).
• Instability evolution under constant acceleration is well-understood, but variable acceleration is relevant for inertial confinement fusion and astrophysics.

Purpose of the Study:

• To study interfacial flow dynamics under time-dependent acceleration profiles.
• To compare flow evolution under smooth (sinusoidal) versus stepwise acceleration profiles.
• To assess the validity of the double-integral-of-acceleration scaling for variable acceleration scenarios.

Main Methods:

• Implicit large-eddy simulations (ILES) were employed.
• Density stratification under time-dependent acceleration was simulated.
• Spatially averaged flow statistics were compared against theoretical scaling.

Main Results:

• The double integral of acceleration effectively distinguishes mean behaviors between stepwise and smooth acceleration profiles.
• Flows subjected to smoother acceleration profiles exhibit quicker self-similar evolution.
• Sinusoidal acceleration profiles provide a more realistic representation of astrophysical and engineering applications.

Conclusions:

• The nature of the acceleration profile significantly impacts Rayleigh-Taylor instability evolution.
• Smoother acceleration profiles accelerate the transition to self-similar flow states.
• The findings have implications for understanding high-energy-density physics and astrophysical processes.