抄録
To clarify the effects of wall regression on the internal flow characteristics of solid rocket motors (SRMs) with complex grain geometries, three-dimensional numerical simulations were performed using the building cube method (BCM) and an Immersed Boundary Method (IBM) to clarify the effects of wall regression on the internal flow characteristics of SRMs. Four grain configurations, including three star-shaped grains representing different stages of combustion and one cylindrical reference model, were analyzed to examine the influence of changes in chamber geometry on flow acceleration and vortex formation. The simulations showed that the star-shaped grains, particularly in the early combustion stages, induced stronger flow acceleration toward the nozzle owing to the narrow chamber and pronounced surface protrusions. The transition region between the grain and nozzle formed cavity-like structures that triggered local flow separation and vortex generation. The Q-criterion visualizations and vorticity magnitude analyses revealed that these vortices were most intense in the early stages and gradually weakened as the chamber geometry became more uniform with continued combustion. The results demonstrate that the time-varying grain geometry significantly affects the internal flow field and vortex behavior within the SRMs. The insights from this study will contribute to the development of optimized grain designs for improved thrust performance and combustion stability.
