Advanced Eulerian Multiphase Modeling of Solid Rocket Motors Flows

Solid rocket motors remain a cornerstone of space propulsion due to their simplicity, reliability, andhigh thrust. From the Space Shuttle to modern launchers such as Ariane 6, Vega C, and the SpaceLaunch 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 multiphaseflows. This complexity is largely driven by the use of aluminized propellants in modern motorsto enhance performance, which produce condensed alumina particles suspended in the gaseousphase. These particles generate a strongly polydisperse and polykinetic flowfield that significantlyinfluences 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 relyon Lagrangian particle-tracking methods, which become computationally expensive for large particlepopulations. This Ph.D. research develops a fully Eulerian multiphase framework using momentmethods derived from the Williams–Boltzmann equation. With appropriate closure strategies, thisformulation captures complex particulate dynamics with near-Lagrangian accuracy while reducingcomputational cost.To assess its accuracy and robustness, the framework is validated against a series of canonical testcases, uncoupled particulate configurations, and one- and two-way coupled simulations representativeof solid rocket motor operating conditions. The results show excellent agreement with high-fidelitynumerical references and benchmark solutions, confirming that the novel fully Eulerian frameworkcan accurately reproduce key multiphase mechanisms.Applications address both motor performance and mechanical nozzle erosion. Two distinctCFD-based approaches are used to predict motor performance. In both cases, model predictionsdeviate by at most ±0.5% from experimental delivered specific impulse. The influence of the dispersedphase model on two-phase losses is also examined, highlighting the sensitivity of performancepredictions to multiphase interactions.Mechanical nozzle erosion is evaluated using the novel Eulerian framework through a parametricstudy of particle size and distribution to assess their effect on erosion. Predictions are comparedwith 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 underrealistic 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 predictionsof particulate dynamics, performance, and mechanical erosion, it provides a powerful tool for thedesign, optimization, and reliability assessment of advanced solid propulsion systems.