Abstract: An underwater shooting experimental platform was built to research the evolutionary characteristics of muzzle flow field of ballistic gun during underwater submerged firing. The direct photography method was used to capture the whole evolution process of the flow field. The high-speed water column in front of bullet produces the water vapor at the muzzle before the bullet comes out of the bore; the under-expanded gas in the bore flows out after the bullet comes out of the bore, and blends with the water vaporto wrap around the bullet; after the bullet leaves from the muzzle, the gas jet continues to expand, and the head of jet is tapered; the surface of bullet is continuously cavitated to generate supercavitation, and at the same time, a slender air column is left at the tail of bullet. On the basis of experiment, a two-dimensional multi-phase flow model is established to simulate the experimental conditions, in which the fluid volume multiphase flow model, standard k-ε turbulence model, dynamic mesh and user-defined functions technology are used. The results indicate that a complex wave structure containing two bottle-shaped shock waves is formed after the highly under-expanded gunpowder gas exits from the muzzle during underwater submerged firing of ballisitc gun. After the bullet leaves from the muzzle, it accelerates continuously in the muzzle flow field. As the bullet moves away from the flow muzzle flow field, the velocity of bullet is continuously attenuated. Key

Key words: ballisticgun, submergedfiring, underwaterfiring, muzzleflowfield, Machdisk, evolutionarycharacteristic, numericalsimulation