Influence of Interior Ballistics for Underwater Guns with Gun-Bullet Coupling Gap

In this paper, the influence of the gun-bullet coupling gap on the internal ballistic characteristics during the full underwater launch of the gun have been studied. The internal ballistic process of setting 0.1 mm gap and no gap is simulated by AUTODYN finite element simulation software. And the internal ballistic process of underwater gun with underwater clearance is simulated using 21, 25 and 30 g propellant. The projectile velocity, pressure inside the barrel and the distribution of components, pressure and velocity of over-gap gas jets during the internal ballistic process are obtained from the simulation, and the simulation results is verified by experiment. The simulation and experimental results show that the proper gun coupling gap can effectively improve the underwater gun launch performance. When the gun-bullet coupling gap is set as 0.1 mm, the gas curtain are all obtained from the propellant with three different masses. Meanwhile, the pressure decreased obviously during the internal ballistic process, and the projectile speed at muzzle is improved significantly, which is beneficial to the production of stable supercavitation warp projectile. The resistance of the projectile moving underwater reduces greatly and the travel of the projectile increases underwater.