弹道枪水下全淹没式发射膛口流场演化特性的数值模拟研究

Numerical Investigation on Evolutionary Characteristics of Muzzle Flow Field of Ballistic Gun during Underwater Submerged Firing

为了解弹道枪水下全淹没式发射膛口流场的演化特性,搭建水下射击实验平台,运用直接摄影法捕捉其膛口流场演变的全过程。实验发现:在弹头出膛前,弹前水柱已经在膛口空化产生水蒸汽;弹头出膛后,膛内燃气流出并与水蒸汽掺混,将弹头包裹;弹头远离膛口后,燃气射流继续膨胀,头部呈锥形;弹头表面不断空化产生水蒸汽,形成超空泡,同时在弹头尾部会留下细长的气柱。在实验基础上建立二维多相流模型,采用流体体积函数多相流模型和标准k-ε湍流模型,结合动网格及用户自定义函数技术,对实验工况进行数值模拟。结果表明:弹道枪水下全淹没式发射时,高度欠膨胀的火药燃气出膛口后,形成了包含两个瓶状激波的复杂波系结构;弹头出膛后,在膛口流场区域内不断加速,随着弹头远离膛口流场区域,弹头速度不断衰减。

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-εturbulence 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.