Phd in AERONAUTICS AND SPACE ENGINEERING

Thesis title: Advanced Eulerian Multiphase Modeling of Solid Rocket Motors Flows

Solid rocket motors remain a cornerstone of space propulsion due to their simplicity, reliability, and high thrust. From the Space Shuttle to modern launchers such as Ariane 6, Vega C, and the Space Launch System, solid boosters have consistently played a critical role in access-to-space architectures, underscoring their enduring strategic and commercial importance. Despite their apparent simplicity, solid rocket motors exhibit highly complex internal multiphase flows. This complexity is largely driven by the use of aluminized propellants in modern motors to enhance performance, which produce condensed alumina particles suspended in the gaseous phase. These particles generate a strongly polydisperse and polykinetic flowfield that significantly influences motor behavior, affecting performance, internal flow structure, and component integrity. Experimental investigations are severely limited by the extreme thermo-mechanical environment, making advanced numerical modeling an essential tool for analysis. However, accurately modeling these multiphase flows remains challenging. Most existing tools rely on Lagrangian particle-tracking methods, which become computationally expensive for large particle populations. This Ph.D. research develops a fully Eulerian multiphase framework using moment methods derived from the Williams–Boltzmann equation. With appropriate closure strategies, this formulation captures complex particulate dynamics with near-Lagrangian accuracy while reducing computational cost. To assess its accuracy and robustness, the framework is validated against a series of canonical test cases, uncoupled particulate configurations, and one- and two-way coupled simulations representative of solid rocket motor operating conditions. The results show excellent agreement with high-fidelity numerical references and benchmark solutions, confirming that the novel fully Eulerian framework can accurately reproduce key multiphase mechanisms. Applications address both motor performance and mechanical nozzle erosion. Two distinct CFD-based approaches are used to predict motor performance. In both cases, model predictions deviate by at most 0.5\% from experimental delivered specific impulse. The influence of the dispersed phase model on two-phase losses is also examined, highlighting the sensitivity of performance predictions to multiphase interactions. Mechanical nozzle erosion is evaluated using the novel Eulerian framework through a parametric study of particle size and distribution to assess their effect on erosion. Predictions are compared with experimental data from the Space Shuttle Solid Rocket Booster, showing strong agreement. These results demonstrate the framework’s ability to accurately capture particle-driven erosion under realistic operating conditions. Overall, this work establishes a robust, accurate, and computationally efficient Eulerian methodology for simulating multiphase flows in solid rocket motors. By enabling high-fidelity predictions of particulate dynamics, performance, and mechanical erosion, it provides a powerful tool for the design, optimization, and reliability assessment of advanced solid propulsion systems.