超高速弹丸膛口流场结构分析

为了计算和分析超高速弹丸膛口流场的分布状况,建立了超高速弹丸从膛底飞离出炮口整个过程的膛口流场二维轴对称数值仿真模型.基于有限体积法,采用分块网格划分的整体运动处理方法,结合结构动网格技术及Realizable k-ε湍流模型,耦合内弹道及后效期过程,利用六自由度运动方程控制弹丸运动,以300 mm平衡炮为例,研究了1 730 m/s发射速度下的超高速膛口流场特性.计算结果表明:超高速运动的弹丸在距膛口3.3 m远处便形成了清晰的初始流场,弹前激波到达炮口处压力达到了3.8 MPa左右.喷射出的火药燃气速度达到2 500 m/s,但火药燃气仍未能追赶并包围弹丸,因此膛口流场对超高速弹丸运动的影响不同于对中低速弹丸运动的影响;膛口形成了由冠状冲击波、弹底激波、反射激波、马赫盘构成的多层次激波、间断面相互叠加的完整波系,该发射条件下的膛口流场异常强烈,波系结构更加明显.

The muzzle flow field induced by hyper-velocity projectile

To analyze the muzzle flow field of hyper-velocity projectile, we established a 2-D axisymmetric numerical simulation model based on the finite volume method. The Navier-Stokes equations are solved on an extended mesh covering the whole computational domain. The holistic movement of a partitioned mesh processing method and realizable k-epsilon turbulence model is used coupling the process of interior ballistic and the Six-DOF UDF program which controls the projectile moving. Taking the 300 mm balanced gun as an example, the simulation results indicate here that the initial flow field has been formed clearly when the projectile is 3.3 m away from muzzle, and the pressure is about 3.8 MPa when the shock wave gets to the muzzle. It is noteworthy that the propellant gas velocity reaches 2 500 m/s but it is still unable to catch up and surround the projectile. So the impact of muzzle flow on the hyper-velocity projectile movement is different from the impact on the low-speed projectile. Subsequently it is formed a completely wave system composed of the multilayer shock wave including coronary blast, shock wave, reflected shock wave, Mach disk and the discontinuity surface, which makes the wave structure and the jet flow field more obvious.