Evolution characteristics of the muzzle flow field in a cased telescoped-ammunition expanding wave gun

As a novel class of ammunition, telescoped ammunition exhibits significant distinctions in muzzle flow field formation mechanisms compared to conventional guns, attributable to its unique charge configuration, two-stage ignition process, and the application of expanding wave technology. This study employs a three-dimensional, unsteady, multiphase flow model, integrated with the k-ε turbulence model to simulate jet mixing phenomena and coupled with the interior ballistic equations specific to expanding wave guns using telescoped ammunition. The model systematically simulates the muzzle flow field structure and the evolution of tail-jet flows during the firing sequence of 40 mm cased telescoped-ammunition expanding wave gun. Numerical results reveal that the muzzle flow field exhibits characteristic under-expanded jet features. The distributions of pressure and temperature clearly delineate the dynamic evolution of the wave system, including the formation of Mach disks, the reflection of expansion waves, and the presence of intercepting shock waves. The tail-jet assembly generates a high-Mach-number expansion region as the inertial breechblock recoils. Propellant gases venting through the inertial breechblock gap induce an initial shock wave, which subsequently develops into a bottle-shaped shock structure. Within a timeframe of approximately 0.5–1.5 ms, the continued expansion of the tail-jet gases forms a flattened, bottle-shaped shock, effectively generating reverse momentum and thereby significantly reducing the gun's recoil. This investigation elucidates the complex aerodynamic effects and shock wave system evolution inherent to telescoped-ammunition discharge, providing a theoretical foundation for the design of related weapon systems.