DEVELOPMENT & APPLICATION OF HYPERSONIC BOUNDARY LAYER TRANSITION PREDICTION & ANALYSIS TOOLS

Abstract

Accurate prediction of boundary layer transition remains a fundamental challenge in hypersonic aerodynamics, where early transition can dramatically increase thermal loads and drag. This dissertation presents the development and application of a suite of advanced computational tools to simulate and analyze transition mechanisms in high-speed boundary layers in a variety of geometries and flow regimes. At the core of this work is a novel high-fidelity framework that combines an Immersed Boundary Method (IBM) with Adaptive Mesh Refinement and Wave Packet Tracking (AMR-WPT). The resulting IBM-AMR-WPT solver enables efficient and robust simulation of the nonlinear disturbance field over complex, fully three-dimensional geometries without the need for body-fitted meshes. This approach retains all nonlinear terms in the governing equations and leverages adaptive mesh refinement to track evolving wave packets, offering significant computational savings compared to traditional Direct Numerical Simulation (DNS). Complementing the IBM-AMR-WPT methodology, a Time Spectral (TS) solver is also adapted to high-enthalpy flows, validated against experiments and employed to study the effects of transpiration cooling on boundary layer transition. The TS approach, based on a harmonic balance formulation of the Navier-Stokes equations, is particularly well-suited for capturing periodic or quasi-periodic disturbance evolution in the linear regime. It provides a powerful alternative to classical Linear Stability Theory (LST) and Parabolized Stability Equations (PSE), especially for configurations where global receptivity and mode interactions are of interest. The combined framework is validated against canonical two- and three-dimensional test cases and then applied to a series of increasingly complex configurations, including finned cones, wavy walls, and the Boundary Layer Transition (BOLT) experiment geometry. The tools are further extended to study particle-induced transition and the impact of transpiration cooling on flow stability. In each case, the simulation framework successfully captures key stages of transition: from receptivity, through linear and nonlinear instability growth, to eventual breakdown to turbulence. The methods and results presented in this dissertation significantly advance the state of the art in transition prediction and provide new physical insights into hypersonic boundary layer behavior. The flexibility, accuracy, and computational efficiency of the tools developed make them valuable assets for both fundamental research and practical aerospace vehicle design.