空心弹高速入水机理及特性数值模拟研究

Numerical simulation study on the mechanism and characteristics of highspeed water entry of hollow projectiles

为分析空心弹高速入水的机理及其特性,基于雷诺时均Navier-Stokes方程、VOF(volume of fluid)多相流模型、Realizable k-ε湍流模型,引入Schnerr-Sauer空化模型和重叠网格技术对空心弹高速入水进行数值模拟研究,获得了通孔孔径和头部形状对空心弹的空化特性、空泡形态和入水运动特性的影响规律。研究显示数值计算的空泡形态和入水速度、位移曲线与实验结果吻合较好,验证了数值模拟方法的可行性。结果表明:当通孔孔径不同时,通孔孔径越大,空化现象越明显,通孔射流越长,但对空泡半径的影响不大;通孔孔径越小,空泡闭合时间越早,与水面碰撞产生的阻力系数峰值越高,空心弹入水稳定后其阻力系数也越大;无量纲直径在0.575~0.600之间时,空心弹的运动最为稳定。当头部锥角不同时,头部锥角越大,空泡直径越大,空化现象出现得越晚,但空化生成的速度更快;随着头部锥角的增大,阻力系数变大,空心弹的速度衰减变快,相同时间运动的距离较短;头部锥角越大,俯仰角的变化越小,空心弹的运动越稳定。

To analyze the mechanism and characteristics of high-speed water entry of hollow projectiles,a numerical simulation study of the high-speed water entry of the hollow projectiles was carried out based on the Reynolds average Navier-Stokes equation(RANS),the volume of fluid(VOF)multi-phase flow model,the realizable k-ε flux model,the Schnerr and Sauer aeration model,the six-degrees-freedom(6-DOF)motion simulation method,and the overlapping grid technology.The effects of through-hole aperture and head shape on the cavitation characteristics,cavity morphology,and water entry kinematic properties of the hollow projectile were obtained.The effectiveness of the calculation method was verified by comparing it with the water entry experiment.The results show that the numerically calculated cavity morphology and water entry velocity and displacement curves are in good agreement with the experimental results,which verify the effectiveness of the numerical simulation method.When the through-hole aperture is different,the larger the through-hole aperture,the more pronounced the cavitation phenomenon and the longer the through-hole jet,but the effect on the radius of the cavity is not significant.The smaller the through-hole aperture,the earlier the closure time,the higher the peak drag coefficient resulting from impact with the water surface,and the greater the drag coefficient after the hollow projectile has stabilized in the water.The movement of the hollow projectile is most stable when the dimensionless diameter is between 0.575 and 0.600.When the head cone angle is varied,the larger the head cone angle,the larger the diameter of the cavity,and the later the cavitation phenomenon begins,but the faster the cavitation is generated.As the head cone angle increases,the drag coefficient becomes larger and the velocity of the hollow projectile decays faster,moving a shorter distance at the same time.However,the larger the head cone angle,the smaller the change in pitch angle and the more stable the motion of the hollow projectile.