月池(Moon pool)係指垂直貫穿船體開口以便進出下方水域作業的特殊船體設計，對甲板上人員及操作器械提供相對安全的環境保護，月池自20世紀中期問世後，多見於油氣鑽井船、海洋調研船，並可應用至水下探勘、深海救援等用途上；不過，月池內大量水量移動，則水與井壁間沖激行為造成船體、甚至甲板受到拍擊與振動等現象，船舶耐海性恐受到不好影響。鑑於國內少見此類月池船型設計，本文旨於探討月池井船配置對船舶遭遇不同波浪條件下之船體運動反應的影響。
本研究方法係建構在於頻率領域下輻射及繞射邊界值問題求解上，採用船舶耐海性能分析常用之二維截片法(Two-dimensional strip method)，針對艉放船(Stern-Launch type)與月池井船(Moonpool type)在不同航行船速以及遭遇多種頻率規則波下的船身起伏(Heave)、橫搖(Roll)與縱搖(Pitch)運動進行數值模擬，當中係以源點分佈法求解流場速度勢，進而計算船體浸水表面上流體受力，經船體運動方程式求得單位波幅下各成分波的運動反應，並透過成份波疊加原理來模擬船舶航行在不規則短峰波中之運動行為。
本文中，海況模擬係採用常見之ITTC雙參數波譜模型，所模擬海況等級涵蓋2至8級，透過剛體運動轉換、分析實際作業點動態加速度，故全船運動反應觀察點除船體重心處外，並觀察兩型船深潛救生艇（Deep Submergence Rescue Vehicle，DSRV）投放點以及遙控無人潛水器（Remotely Operated Underwater Vehicles，ROV）的A架底座等位置側向與垂向加速度。
本研究數值分析結果顯示，雖月池井船與艉放船在重心處起伏及縱搖運動反應沒有明顯差異，不過兩船重心處橫搖反應峰值大小與位置不同；若同時疊合海況波譜與橫搖反應解作觀察，可發現相對於艉放船，月池井船橫搖峰值處離波譜峰值處較遠，代表兩者重疊範圍少，所誘發橫搖運動的波浪能量小，則月池井船遭遇海況時橫搖反應幅度比較緩和、抗浪性佳。另外，在DSRV與ROV等潛水器投放作業點加速度觀察上，雖兩型船在ROV作業點的加速度值月池井船略高於艉放船但差異不明顯，而兩型船在DSRV作業點，月池井船在各海況下的垂向與側向加速度皆低於艉放船；整體而言，月池井船的確展現出較優異平台穩定性，且具備更友善操作環境，適合擔任潛水器支援母船。

Moonpool in vessels is a feature design, which is the vertical opening through the hull, for convenient access to the water below hull bottom, and aims to safely launch and recover the underwater vehicles. However, in addition to caused slamming and vibration on hull, sloshing due to severe water movements inside moonpool affects ship stability in waves. To understand the moonpool influence on seakeeping performance, the numerical analysis of ship motion is considered to investigate the motion behaviors of vessels with and without moonpool in present study.
The well-known strip method is utilized to solve the flow velocity potential and hydrodynamic forces on hull. Consequently, the reacting hydrodynamic and restoring forces are substituted into motion equation to have motion Response Amplitude Operator （RAO） at vessel’s center of gravity. Furthermore, the absolute motion responses at specific locations onboard in various sea states, simulated by ITTC wave spectrum, are comprehensively analyzed to investigate the short-crested results of the vessels of Moonpool type（MP）and Sten-launch type（ST）, in which underwater vehicles launching is in moonpool zone and aft-zone, respectively.
The motion RAO comparison for MP and ST vessels reveals that deviation in heave and pitch is small, but apparent for roll motion in beam sea. Furthermore, it is noted that the peak in roll RAO of MP vessel generally gets distant from the peak of wave spectrum, and it is expected that the less roll response of MP vessel when operating in rough sea. In addition, the acceleration at operation point of DSRV on MP vessel is apparently smaller than ST vessel, although induced accelerations at ROV seat point for both vessels are close. Finally, it concludes that moonpool design is advantageous in seakeeping performance and ensures safety for underwater vehicles operation.

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