Date of Award
2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Mechanical and Aerospace Engineering
Committee Chair
Jason Cassibry
Committee Member
Dale Thomas
Committee Member
Saroj Kumar
Committee Member
Keith Hollingsworth
Committee Member
Robert Frederick
Research Advisor
Jason Cassibry
Subject(s)
Two phase flow--Computer simulation, Nuclear propulsion, Equations of state, Hydrodynamics
Abstract
This dissertation presents the development of a predictive simulation framework for analyzing gas-liquid dynamics in Centrifugal Nuclear Thermal Propulsion (CNTP) systems, where hydrogen gas is injected into a rotating liquid uranium fuel core. Using Smoothed Particle Hydrodynamics (SPH), a fully Lagrangian mesh-free method, this research models multiphase flow behavior under extreme conditions, capturing critical phenomena such as bubble formation, surface deformation, void fraction evolution, and rotational confinement. A novel modification to the liquid equation of state is introduced to mitigate SPH artifacts, improving fluid stability and enabling surface recovery after deformation. The model is validated against experimental data from static water-air injection setups, with good agreement observed in bubble rise trends and void fraction scaling. The validated approach is then extended to simulate uranium-hydrogen interactions under high rotation, reproducing theoretical centrifugal equilibrium and hollow annular fluid shell formation. Additionally, analytical corrections for hydrostatic forces and drag are implemented to reduce empirical tuning and enhance predictive capability. While the model currently underestimates terminal velocity and exhibits minor instability under extreme conditions, it successfully captures major multiphase trends and offers a scalable platform for future integration with thermal and reactivity models. This work addresses a critical gap in modeling two-phase flow in CNTP by providing a versatile and extendable tool for predicting bubble behavior in rotating nuclear systems. It also demonstrates the feasibility of using SPH for complex fluid scenarios relevant to space propulsion where experimental access is limited. The findings of this study contribute to the design optimization of CNTP reactors and lay the groundwork for broader simulation efforts aimed at enabling faster, safer, and more efficient interplanetary missions.
Recommended Citation
Darakorn na Ayuthya, Pongkrit, "An algorithm for three-dimensional bubble simulations and analysis for advanced nuclear propulsion" (2025). Dissertations. 466.
https://louis.uah.edu/uah-dissertations/466