A STUDY OF THE ACCELERATION TRANSFER INTERFACE AND ITS INFLUENCE ON THE BOUNDARY LAYER TRANSITION AND DRAG CHARACTERISTICS OF A 30 MM KINETIC ENERGY PROJECTILE

This study investigates the influence of the acceleration transfer interface on boundary layer transition and drag characteristics of a 30 mm kinetic energy projectile (KEP) using an allspeed transition model. The acceleration transfer interface, represented by annular grooves, imparts force and acceleration to the projectile during its launch but also interacts aerodynamically with the projectile's external flow and influences its performance. The presence of grooves introduces complex flow interactions, including micro-shocks, pressure fluctuations, and local flow separation, which affect the boundary layer state and drag. Since the terminal effectiveness of the projectile depends on the impact velocity, reducing the velocity decay due to the drag is an efficient way to improve the aerodynamic performance of the projectile. Numerical simulations reveal that grooves in the laminar boundary layer trigger the early transition and increase the friction drag, while those in the turbulent boundary layer have a minimal impact on the friction drag. The early transition due to grooves in the laminar boundary layer amplifies shear stress and turbulent energy production, degrading efficiency. These findings aid in optimizing groove geometries and location to minimize the drag while ensuring effective acceleration transfer, with implications for high-speed projectile design and ballistic efficiency improvements.