【摘要】 筒口气团对水下航行体出筒过程流场与载荷特性具有重要影响。本文通过数值模拟方法，将该过程简化为航行体在垂直静止的筒中突然起动，并以定速穿越气团的过程，研究了其流场与力学特性。主要结果如下：筒口气团受航行体出筒挤压、驱赶、穿越与卷吸，在筒口平台及航行体周围形成振荡的环状气泡，筒口流场具有强烈的非定常涡运动特征；由环状气泡诱导的压力振荡影响整个流场，该压力随时间与距离衰减；流场振荡压力可近似认为线性叠加在航行体表面原有绕流压力上，使出筒过程中航行体母线上周期性地出现逆压梯度，这会影响可能在物面上出现的流动分离与空泡；在以气团当量球体直径和航速为特征量定义的无量纲时间下，不同气团体积的航行体振荡受力特性达到了归一化。更多还原

【Abstract】 The stored air mass(i.e. muzzle gas cloud) ahead of a projectile nose in a vertical launch tube has significant influences on the flow field and loads during underwater launching. In this paper the process was simplified to an impulsively started projectile in a stationary vertical tube, which then passied through air mass with constant velocity. The flow was investigated using numerical simulation. The primary conclusions are as follows: The air mass is compressed, pushed out, entrained, and finally forms an annular oscillating bubble, which is accompanied by intense unsteady vortex around the muzzle platform and the projectile. The oscillating pressure induced by the bubble propagates through the flow field and attenuates with time and distance. The oscillating pressure can be considered as being linearly superimposed on original flow pressure,resulting in a periodic adverse pressure gradient along the projectile surface, which affects flow separation and cavitation. The oscillating drag coefficient for different volumes of the air mass can be normalized by dimensionless time defined using the velocity and equivalent spherical diameter of the air mass.更多还原