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| Effects of Water Entry Angle on Cavity Characteristics of High-speed Sphere |
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| DOI：10.7643/issn.1672-9242.2023.03.001 |
| KeyWord:cavity of water entry sphere water entry angle high-speed water entry motion characteristics impact of water entry |
| Author | Institution |
| LI Li-jian |
School of Mechanical Engineering, Beijing Institute of Technology, Beijing , China |
| ZHANG Min-di |
School of Mechanical Engineering, Beijing Institute of Technology, Beijing , China |
| WANG Zhan-ying |
Beijing Institute of Astronautical System Engineering, Beijing , China |
| HUANG Biao |
School of Mechanical Engineering, Beijing Institute of Technology, Beijing , China |
| LIU Si-hua |
School of Mechanical Engineering, Beijing Institute of Technology, Beijing , China |
| TAN Zhen-kun |
School of Mechanical Engineering, Beijing Institute of Technology, Beijing , China |
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| Abstract: |
| The work aims to study the evolution and motion characteristics of cavity during the high-speed water entry process of the sphere to provide theoretical reference for projectile entering water or dropping torpedo into water. Based on the experimental and numerical simulation, the formation, closure, collapse of cavity and motion characteristics of sphere during the water entry process of sphere were discussed. The results showed that according to the morphological characteristics of the cavity, there were four stages of cavity developing process, namely water-entry impact, cavity formation, cavity closure and cavity collapse. During water entry impact, the pressure at the spherical head was the maximum. With the decrease of the water entry angle, the pressure of the spherical head decreased gradually. After closure of cavity, the cross-section area of the cavity decreased with the increase of the water entry angle. In the collapsing stage, a reentrant jet was generated due to the cavity clamping and the strength of the reentrant jet decreased with the decrease of the water entry angle. Especially, a reentrant jet did not occur under 30° of water entry angle. Moreover, there was deflection of the underwater spherical trajectory when the sphere entered water at different angles. And the degree of deflection decreased with the increase of the water entry angle. When the sphere entered water vertically, there was no deflection. It is concluded that the water entry angle has great effect on the evolution process and motion characteristics of cavity in the process of high-speed water entry. The smaller the water entry angle is, the larger the cross-section area of cavity after water entry, the larger the total flow drag coefficient Cd, and the more serious the deflection of the sphere’s motion trajectory. |
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