Objectives Fragment is the key object of vessel liquid tank protection, and the study on the water-penetrating velocity attenuation characteristic of the high-speed "pie" fragment can provide theoretical reference for the protection analysis and optimization of the vessel liquid tank.
Methods First to consider the change in resistance coefficient during water-penetrating process of fragment, the classical theoretical formula is modified by introducing the empirical coefficient a and b. Then, numerical simulation method is used to simulate the water-penetrating process of fragment, and the simulation results are compared with the calculation results from classical theoretical formula and improved formula. Finally, the influences of the initial velocity and slenderness ratio on the fragment penetration velocity attenuation are studied by the empirical coefficient a and b.
Results The improved formula is more suitable than the classical formula to study the attenuation characteristics of the water-penetrating velocity of the "pie" fragment. The resistance coefficient is related to the slenderness ratio:when the slenderness ratio is less than 0.5, the resistance coefficient is greatly affected by the change of the penetration distance; when the slenderness ratio is greater than 0.5, the resistance coefficient is less affected by the change of the penetration distance, and the resistance coefficient can be treated as a constant.
Conclusions The protective effect of vessel liquid tank on "pie" fragment can be calculated simply by using the improved theoretical formula in this paper.
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