Hydrodynamic Loads and Dynamic Behavior of Offshore Structures in Current and Waves

Research Project

Project/Area Number	03402040
Research Category	Grant-in-Aid for General Scientific Research (A)
Allocation Type	Single-year Grants
Research Field	船舶抵抗・運動性能・計画
Research Institution	University of Tokyo
Principal Investigator	FUJINO Masataka University of Tokyo Faculty of Engineering, Professor, 工学部, 教授 (10010787)
Co-Investigator(Kenkyū-buntansha)	EGUCHI Sumihiro University of Tokyo Faculty of Engineering, Assistant, 工学部, 助手 (00013201) MAEDA Hisaaki University of Tokyo Institute of Industrial Science,Professor, 生産技術研究所, 教授 (80013192) KAGEMOTO Hiroshi University of Tokyo Faculty of Engineering, Associate Professor, 工学部, 助教授 (40214275) 木下健東京大学, 生産技術研究所, 助教授 (70107366) 吉田宏一郎東京大学, 工学部, 教授 (90010694) 浦環東京大学, 生産技術研究所, 助教授 (60111564) 深沢塔一東京大学, 工学部, 助教授 (80143171)
Project Period (FY)	1991 – 1992
Project Status	Completed (Fiscal Year 1992)
Budget Amount *help	¥19,600,000 (Direct Cost: ¥19,600,000) Fiscal Year 1992: ¥6,200,000 (Direct Cost: ¥6,200,000) Fiscal Year 1991: ¥13,400,000 (Direct Cost: ¥13,400,000)
Keywords	Combined external forces / Offshore structures / Low speed control of towing carriage / Hydrodynamic forces
Research Abstract	In order to clarify the hydrodynamic loads and dynamic behavior of offshore structures placed in complicated natural environment, it is necessary to establish a reasonable and accurate method of evaluating the hydrodynamic forces caused by simultaneous action of wave, wind and current. Especially, it is important and urgent to establish a method of predicting the hydrodynamic forces acting on offshore structures in current and waves. Meanwhile, it is not easy to make current and wave at the same time in water basin. Therefore, in the present investigation, the current movement was substituted by moving an offshore structure at a prescribed slow speed corresponding to current velocity. For this purpose, a new control apparatus of towing carriage, which is able to make the towing carriage move at very low speed (0-0.2m/sec), was developed by the aid of the present Grant-in-Aid for Scientific Research and then installed on the existing towing carriage in 1991. In 1992, the hydrodynamic forces on an oscillating articulated column were investigated. The forced oscillation consisting of tow different harmonic components was realized by making simultaneous use of the towing carriage with the new control apparatus, and an existing planar motion mechanism. As the result, it was found that the inertia force coefficients for two kinds of harmonic motions are fairly equal to each other, and they are exactly the same as the inertia force coefficient obtained by the simple harmonic forced oscillation. In addition, the hydrodynamic characteristics of a permeable offshore structures were investigated by making use of the above-mentioned towing carriage.