• 한국군사과학기술학회지
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• 제13권6호
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• pp.1026-1033
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• 2010

The analysis of water-entry impact forces acting on the fin shaft of high speed water-entry body is described. During the entry of high speed body into water, the physical phenomenon and flow properties are analyzed. A proper analysis model is established and the method to estimate the flow force which causes impact torque at the fin shaft is described. It is assumed that the fin shaft is damaged by the force which is induced by contacting with cavity wall. The pressure distribution of fin and the maximum torque are estimated and compared with breaking force. Conclusively, it is hard to resist water-entry impact force in terms of the reinforcement of fin shaft. Additionally safe equipment is essentially required.

• 한국가시화정보학회지
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• 제24권1호
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• pp.27-38
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• 2026

In this study, the water entry dynamics of free-falling bodies with varying geometries were experimentally investigated using high-speed shadow imaging techniques. The effects of fore body shape on cavity formation, evolution, collapse, and post-entry hydrodynamic performance were systematically analyzed. A series of drop tests was conducted using spherical and four distinct axisymmetric models (flat, cusp, round, and ogive) under controlled initial impact velocities. The results demonstrate that the fore body geometry critically influences splash characteristics, cavity stability, re-entrant jet formation, and resultant hydrodynamic forces. Streamlined shapes, such as ogive exhibited slender and stable cavities with delayed pinch-off, leading to reduced drag and improved straight-line motion. In contrast, blunt shapes, such as flat and cusp, induced early cavity collapse, strong re-entrant jets, and increased hydrodynamic resistance. The experimental findings offer valuable insights into optimizing projectile and underwater vehicle designs for enhanced hydrodynamic efficiency and structural integrity during water entry.