Dissertation/Thesis Abstract

Adaptive Wavelet-Based Direct Numerical Simulations of Rayleigh-Taylor Instability
by Reckinger, Scott J., Ph.D., University of Colorado at Boulder, 2013, 147; 3562033
Abstract (Summary)

The compressible Rayleigh-Taylor instability (RTI) occurs when a fluid of low molar mass supports a fluid of higher molar mass against a gravity-like body force or in the presence of an accelerating front. Intrinsic to the problem are highly stratified background states, acoustic waves, and a wide range of physical scales. The objective of this thesis is to develop a specialized computational framework that addresses these challenges and to apply the advanced methodologies for direct numerical simulations of compressible RTI. Simulations are performed using the Parallel Adaptive Wavelet Collocation Method (PAWCM). Due to the physics-based adaptivity and direct error control of the method, PAWCM is ideal for resolving the wide range of scales present in RTI growth. Characteristics-based non-reflecting boundary conditions are developed for highly stratified systems to be used in conjunction with PAWCM. This combination allows for extremely long domains, which is necessary for observing the late time growth of compressible RTI. Initial conditions that minimize acoustic disturbances are also developed. The initialization is consistent with linear stability theory, where the background state consists of two diffusively mixed stratified fluids of differing molar masses. The compressibility effects on the departure from the linear growth, the onset of strong non-linear interactions, and the late-time behavior of the fluid structures are investigated. It is discovered that, for the thermal equilibrium case, the background stratification acts to suppress the instability growth when the molar mass difference is small. A reversal in this monotonic behavior is observed for large molar mass differences, where stratification enhances the bubble growth. Stratification also affects the vortex creation and the associated induced velocities. The enhancement and suppression of the RTI growth has important consequences for a detailed understanding of supernovae flame front acceleration and fuel capsule designs for inertial confinement fusion.

Indexing (document details)
Advisor: Vasilyev, Oleg V.
Commitee: Crimaldi, John P., Hamlington, Peter E., Kassoy, David R., Livescu, Daniel
School: University of Colorado at Boulder
Department: Mechanical Engineering
School Location: United States -- Colorado
Source: DAI-B 74/09(E), Dissertation Abstracts International
Subjects: Applied Mathematics, Mechanical engineering, Physics
Keywords: Compressibility, Computational framework, Rayleigh-taylor instability, Stratification, Vorticity production, Wavelets
Publication Number: 3562033
ISBN: 978-1-303-09446-0
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