Modeling and optimization of projectile in-bore motion based on a coupled method of interior ballistic multiphase flow and launch dynamics

Mechanical interactions between the projectile and barrel during weapon system launch, such as projectile axis oscillation and the contact-collision between the bourrelet band and barrel, negatively impact strike accuracy and flight stability. To investigate the nonlinear behavior of the projectile under varying charge, projectile, and barrel parameters, this study proposes a coupled ballistic model based on the interior ballistic theory of gas–solid two-phase flow and launch dynamics. The model captures the multi-degree-of-freedom characteristics of in-bore projectile motion. Given the complexity of contact interactions involving objects with intricate geometries in small gaps, a rigid-body collision model is introduced to handle the contact-collision between the bourrelet band and barrel. By performing coupled calculations, the final coupled motion equations of the entire system are solved. Additionally, an improved non-dominated sorting whale optimization algorithm is employed to optimize key coupling parameters, reducing the number of collisions while maintaining high projectile velocity and low chamber pressure, thereby enhancing launch stability. The algorithm incorporates adaptive weighting and disturbance factors to balance global and local search capabilities. The results demonstrate that the coupled model effectively captures the translational and rotational characteristics of the projectile within the propulsion system, while the improved whale optimization algorithm successfully addresses the specific tri-objective optimization problem.