Date

2015

Document Type

Thesis

Degree

Master of Science

Department

Mechanical Engineering

First Adviser

Banerjee, Arindam

Abstract

Rayleigh Taylor Instability (RTI) occurs at the interface between a light fluid and a heavy fluid due to the gravitational impact and is commonly observed in several natural and engineering processes like internal confinement fusion (ICF), Type Ia supernova formation and in turbulent combustion processes. Traditionally, RTI has been studied under a constant acceleration frame-work, primarily due to the need of understanding the instability as it occurs in climate and geologic dynamics as well as in deep sea oceanic currents. However, there exists several applications like blast waves, ICF and stellar dynamics where gravitational variability alters the dynamics of the RTI induced mixing process. It is thus important to understand the late-time evolution of RTI under variable acceleration and in cases where the acceleration changes sign.Our primary motivation is to investigate of the effects of initial conditions on self-similar evolution to turbulence of RTI under variable acceleration histories. Incompressible, three dimensional RTI is modeled using a massively parallel high resolution code, MOBILE which uses an Implicit Large Eddy Simulation (ILES) technique. In the current work, four different initial conditions are investigated to understand the effect of spectral bandwidth and spectral index on the late time evolution of the instability as it undergoes multiple acceleration reversals. Our goal is to identify the similarities and differences between the Rayleigh–Taylor turbulence and the more general forms of quasi-stationary turbulence. We will discuss on our results, include low order metrics like, growth constant, molecular mixing parameter and second order moments and anisotropy tensors.

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