头型对射弹高速入水稳定性的影响

Influence of nose shapes on high-speed water entry stability of projectile

针对不同头型射弹高速倾斜入水阶段和水下夹带空泡航行阶段空泡演化特性及入水稳定性展开研究,以便为高速射弹、空投鱼雷等跨介质武器高精准打击目标提供理论依据。结合高速全流场观测技术与数值模拟分析,通过对比圆柱平头、半球头和90°锥头3种头型射弹高速倾斜入水过程,着重讨论射弹头型对入水空泡形态、空泡尺寸、运动速度、俯仰角和入水稳定性的影响规律。研究表明:尽管3种射弹的入水和水下夹带空泡航行过程相同,但头型对射弹高速倾斜入水时的空泡特性和入水稳定性具有显著影响。在入水阶段,圆柱平头射弹入水空泡直径最大,90°锥头射弹次之,半球头射弹最小;入水冲击载荷的大小按照圆柱平头射弹、半球头射弹和90°锥头射弹的顺序递减。在水下带空泡航行阶段,圆柱平头射弹入水空泡长径比最大值为7.187,空泡为直径大且长度小形态;半球头射弹入水空泡与之相反,最大长径比高达10.864,空泡呈现为细长形状;而90°锥头射弹夹带空泡因壁面遭到破坏,形态极不稳定。在整个入水过程中,半球头射弹入水稳定性最优,圆柱平头射弹次之,90°锥头射弹入水稳定性最差。

Cavitation evolution characteristics and water entry stability of projectiles with different nose shapes during high-speed oblique water entry impact and underwater navigation phases with cavitation are studied to provide a theo⁃retical basis for high-speed projectiles,air-dropped torpedoes and other trans-medium weapons to attack targets with high accuracy.Combined with high-speed full flow field visualization experiments technology and numerical simulation analysis,influence of projectile nose shapes on water entry cavitation shapes,cavitation size,movement speed,pitch angle and water entry stability is emphatically discussed by comparing the high-speed oblique water entry process of projectiles with three different nose shapes.Comparison involves cylindrical flat nose,hemispherical nose and 90°cone nose.Results show that although the process of water entry and underwater navigation with cavitation of the three projectiles are the same,the nose shape has a significant influence on water entry cavitation characteristics and water entry stability of projectiles during high-speed oblique water entry.In the water entry phase,the water entry cavi⁃tation diameter of the cylinder flat nosed projectile is the largest,followed by the 90°cone nosed projectile,and the smallest being the hemispherical nosed projectile.The water entry impact load decreases in the order of cylindrical flat nosed projectile,hemispherical nosed projectile and 90°cone nosed projectile.During the underwater navigation phase with cavitation,the maximum length-to-diameter ratio of the water entry cavitation of the cylindrical flat nosed projectile reaches 7.187,which is large in diameter and short in length;on the contrary,the maximum length-to-diameter ratio of the water entry cavitation of the hemispherical nosed projectile is as high as 10.864,and the cavita⁃tion shows a slender shape.However,the cavitation shape of the 90°cone nosed projectile is extremely unstable due to the destruction of the cavitation wall.In the whole water entry process,the hemispherical nosed projectile has the best water entry stability,followed by the cylindrical flat nosed projectile,and the 90°cone nosed projectile has the worst water entry stability.