艙間局部充水對船舶撞擊之抗撞能力影響

Effects of Partially Filled Liquid Tanks in Ship-Ship Collision

船舶艙間充水未滿之自由液面隨著船體運動而晃蕩拍擊艙壁，形成液面沖激現象，它是一種非常複雜的流體運動，其沖激力與沖激週期隨艙間幾何形狀與船體運動狀態而異。本文分析重點為探討船舶撞擊過程未充滿液體艙間之自由液面流體晃蕩與拍擊對於結構撞擊損壞之影響，不在探討液面晃蕩之沖激現象，因此配合水面沖激效應之週期性沖激壓力，將流體運動以等效「彈簧──質量──阻尼」系統代替部份充水艙間的水面沖激效應之吸能與沖激力效應。本文探討8,000 TEU貨櫃船機艙段遭受同級貨櫃船側向撞擊過程的結構損壞與衝擊狀況，比較4種不同艙間充水狀況，在碰撞後，撞擊船之船艏與被撞船之機艙段產生的破壞狀況。本文以LS-DYNA非線性有限元素程式進行船舶碰撞分析，分析結果顯示艙間局部充水沖激效應可吸收部分能量，佔整體損壞吸能比例雖不高，但水面沖激力影響可提高抗撞能力，降低撞擊破壞程度。 Sloshing effects occur in a partially filled fluid tank due to the motion of free surface. The hydrodynamics of sloshing is very complicated. The impact forces and periods of free surface sloshing depend on the tank shape and motion types. This study focus on the crashworthiness of the ship structures influenced by the sloshing effects of partially filled liquid tank, not on the sloshing phenomenon in ship-ship collision. Considering the periodic sloshing pressure, an equivalent spring-mass-damper model is used to simulate the sloshing effect. In this paper, the damage of structures for an 8,000 TEU container ship striking the engine room section of the similar size of container ship was investigated. Four different collision scenarios with different condition of partially filled water tanks were considered to compare the damages of the striking ship's bow and the struck ship's hull in the collisions. The LS-DYNA nonlinear finite element analysis program was used to analyze the structural damage during the ship collision in this paper. The analysis result shows that the energy absorbed by sloshing effects is small; however, it indeed can improve the crashworthiness and reduce the structure damages in ship collision.