Dynamic Analysis of Flexible Floating Platform

本研究針對海面型撓性平台進行相關之動力分析，包括平台設計、平台與波浪交互作用之動力現象，作一系列的討論以應用於海面型黑潮電廠。首先針對單元平台之萬向接頭勁度及平台與波浪週期、振幅之關係進行探討，而後簡化單元平台比較平台與波浪間之基本特性。並設計平台之萬向接頭勁度、聯桿尺寸以因應渦輪機對平台之力學影響。結果發現單元平台簡化與否皆可能與波浪發生類共振現象，主要由平台之物理特性與入射波之週期決定，因此萬向接頭勁度的改變可能影響單元平台對於不同頻率入射波之運動表現。 完成單元平台之設計及力學分析後，以測試平台研究渦輪機對於平台之影響，分別以四種錨固方式及三種渦輪機佈放方式進行探討。分析發現平台中心之垂直平衡位置並不會受到錨固及渦輪機佈放方式的影響，說明在固定渦輪機數量下，平台中心之垂直平衡位置並不會有所改變。而渦輪機佈放方式主要影響平台聯桿之垂直平衡位置，結果顯示渦輪機掛載於平台同側時前後聯桿之垂直平衡位置差為0.36公尺，約為其餘兩種配置方式之30倍。錨固方式測試結果發現交錯型纜繩配置對於平台的影響較外放型配置小，由於交錯式的纜繩配置使得前方聯桿受波浪力與纜繩力水平分量方向相同，導致平台側向變形量小且能有效控制前後聯桿之垂直位移差。因此建議平台的錨固方式以交錯型纜繩配置作為海面型黑潮電廠的選擇。The dynamic analysis of flexible floating platform including the design of the platform and the interactions between sea wave and the platform has been presented. The unit platform is first investigated using the computational fluid dynamics (CFD) software with the parameters including the stiffness of the universal joints in the platform, wave period and amplitude. The unit platform is then simplified to determine the stiffness of the universal joints, platform dimensions with the turbine forces exerted. The results show that the unit platform deforms extremely under certain wave frequency whether the platform is simplified or not. Hence, the dynamic behavior of the platform is strongly associated with the stiffness of the universal joints under all kinds of wave conditions. The test platform (formed by 1*3 unit platforms) with four kinds of mooring and three types of turbine distribution is then analyzed. It is shown that the mooring type and the turbine distribution have no effect on the vertical equilibrium position of the platform center. The turbine distribution majorly affects the vertical equilibrium position of the fore and aft linkages. The difference in the vertical equilibrium position between the fore and aft linkages with all turbines at the same side is 0.36 meter, which is about 30 times than the other two types of turbine distribution. Also the cross-typed mooring is much stable than the conventional mooring type due to the same direction of the wave drift force and the horizontal component of the cable force, which leads to smaller side deformation of the platform and better control over the fore and aft linkages. Therefore it is suggested that the cross-typed mooring apply on the surface-typed Kuroshio power plant for better platform stability.致謝........................................................................................................................ i 摘要........................................................................................................................ ii Abstract.................................................................................................................. iii 目錄........................................................................................................................ v 圖目錄.................................................................................................................... vii 表目錄.................................................................................................................... x 符號說明................................................................................................................ xi 第一章緒論........................................................................................................ 1 1.1 研究背景................................................................................................ 1 1.2 文獻回顧............................................................................................... 2 1.2.1 黑潮洋流概況..................................................................................... 2 1.2.2 波浪與物體之交互作用...................................................................... 3 1.3 研究方法................................................................................................ 5 第二章理論模型................................................................................................ 8 2.1 線性化波浪模型.................................................................................... 9 2.2 二階非線性波浪理論............................................................................ 11 2.3 物體受力及扭矩(流體靜壓力) ............................................................ 12 2.4 物體受力(輻射及繞射波浪力) ............................................................ 13 2.5 纜繩受力................................................................................................ 15 2.6 AQWA 模組........................................................................................... 15 第三章單元平台動力分析................................................................................ 17 3.1 勁度測試................................................................................................ 21 3.2 週期測試................................................................................................ 31 3.3 振幅測試................................................................................................ 36 3.4 結果討論................................................................................................ 40 第四章簡化版單元平台動力分析.................................................................... 41 4.1 勁度測試............................................................................................... 43 4.2 週期測試................................................................................................ 47 4.3 振幅測試................................................................................................ 49 4.4 結果討論................................................................................................ 52 第五章測試平台動力分析................................................................................ 53 5.1 纜繩與渦輪機佈放設計........................................................................ 54 5.2 測試平台之錨固方式比較.................................................................... 58 5.3 結果討論............................................................................................... 61 第六章結論........................................................................................................ 62 6.1 結論........................................................................................................ 62 6.2 未來展望................................................................................................ 63 參考文獻................................................................................................................ 6