Electronic Thesis/Dissertation
 

Application of High Fidelity Methods to Nuclear Engineering Thermal-Hydraulics Problems

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identification of critical impediments to application of non-uniform Fast Fourier Transform based Poisson solvers

The design and safety analysis of nuclear reactors are increasingly challenged by multiscale, transient thermal-hydraulic phenomena that exceed the capabilities of traditional semi-empirical system codes. This dissertation advances direct numerical simulation as a credible and indispensable “numerical laboratory” capable of resolving these complexities. By systematically addressing foundational barriers of software maintainability, numerical scalability, and the resolution of sub-grid physics, this work establishes a high-fidelity pathway for evaluating safety margins in both design-basis and severe accident scenarios. The research is organized around four primary contributions

refactoring legacy simulation frameworks into a modern, maintainable architecture

characterization of transient heat transfer in molten pool convection

and development of a mechanistic sub-turbulence closure for the nucleate boiling ebullition cycle. A key finding includes the discovery that internally heated molten pools, representative of core debris, appear not to exhibit the transient heat transfer overshoots and hysteresis seen in canonical boundary-heated systems, suggesting a greater resilience in current safety correlations. By bridging the gap between fundamental fluid dynamics and engineering-scale safety challenges, this work demonstrates the physical insights that are gained from resolving the smallest scales of turbulence and heat transfer are invaluable.

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