Characteristics of velocity attenuation and cavity expansion induced by horizontal water-entry of truncated-ogive nosed projectiles
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摘要: 用轻气炮设备对截卵形弹进行了速度在100~150 m/s的水平入水实验，利用高速相机记录了整个入水过程，获取了截卵形弹体在水中运动的速度衰减规律，并对平头弹、卵形弹及截卵形入水弹道稳定性及速度衰减规律进行了对比，对截卵形弹体入水形成的空泡扩展行为进行了理论研究，建立了关于空泡扩展的理论模型，得到了固定位置和固定时间处空泡扩展半径、速度分别与时间和侵彻距离的关系，实验数据与理论计算吻合很好。Abstract: In this paper, the horizontal water-entry experiments of truncated-ogive projectiles at the velocity range of 100~150 m/s were conducted using a light-gas gun and a high-speed camera to record the whole water-entry process. The characteristics of the velocity attenuation and the drag coefficients of truncated-ogive projectiles were obtained, and the trajectory stability and the characteristics of velocity attenuation for the flat-nosed, the ogive-nosed and the truncated ogive-nosed projectiles were compared and analyzed. The cavity expanding behaviors induced by the truncated ogive-nosed projectile's water entry were studied and a theoretical model of the cavity expansion was established. The relationships between the radial cavity radius, cavity wall velocity and time, penetration distance at fixed locations and fixed times were obtained, and good agreements were found between the experimental observations and the theoretical analysis.
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Key words:
- truncated-ogive projectile /
- water-entry /
- drag coefficient /
- velocity attenuation /
- cavity expansion
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图 1 实验设置及截卵形弹体示意图
Figure 1. Schematic of experimental set-up and truncated-ogive projectile
图 2 卵形弹入水及空泡扩展过程
Figure 2. Processes of the ogival projectile entering the water and its cavity expansion
图 3 截卵形弹入水及空泡扩展过程
Figure 3. Processes of the truncated-ogive projectile entering the water and its cavity expansion
图 4 平头弹入水及空泡扩展过程
Figure 4. Processes of the flat-nosed projectile entering the water and its cavity expansion
图 5 不同头型弹体速度衰减随时间变化关系
Figure 5. Relation between velocity attenuation and time for different nose-shaped projectiles
图 6 弹体水平入水空泡扩展模型
Figure 6. The cavity growth model for projectile's horizontal water-entry
图 7 截卵形弹入水后固定点空泡半径随时间的变化
Figure 7. Cavity radius at fixed locations varied with time after truncated-ogive projectile's water-entry
图 8 截卵形弹入水后固定点空泡半径随侵彻距离的变化
Figure 8. Cavity radius at fixed locations varied with penetration distance after truncated-ogive projectile's water-entry
图 9 不同侵彻距离点上Δp的值
Figure 9. The values of Δp at different locations along the penetration distance
图 10 不同时刻对应位置处空泡截面径向扩展速度随时间的变化
Figure 10. Relation between radial expansion velocity of cavity wall and time at different locations
图 11 在特定时刻空泡半径沿侵彻距离的变化
Figure 11. Variation of cavity radius with penetration distance at fixed time
表 1 不同时刻对应的Δp和N
Table 1. The values of Δp and N at different locations
t0/ms Δp/Pa N 1.42 1.14×105 1.362 10 1.89 1.19×105 1.391 97 2.36 1.15×105 1.413 47 
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