Grant-in-Aid for Scientific Research (B)
|Allocation Type||Single-year Grants |
|Research Institution||HIROSHIMA UNIVERSITY |
TAKAKI Mikio Hiroshima University, Graduate School for Engineering, Professor, 大学院・工学研究科, 教授 (00038556)
IWASHITA Hidetsugu Hiroshima University, Graduate School for Engineering, Associate Professor, 大学院・工学研究科, 助教授 (60223393)
FUJIKUBO Masahiko Hiroshima University, Graduate School for Engineering, Professor, 大学院・工学研究科, 教授 (30156848)
SAITO Kimio Hiroshima University, Graduate School for International Development and Cooperation, Professor, 大学院・国際協力研究科, 教授 (50029279)
SAKUNO Yuji Hiroshima University, Graduate School for Engineering, Research Associate, 大学院・工学研究科, 助手 (20332801)
今井 康貴 広島大学, 大学院・国際協力研究科, 助手 (90284231)
|Project Period (FY)
2000 – 2002
Completed (Fiscal Year 2002)
|Budget Amount *help
¥8,500,000 (Direct Cost: ¥8,500,000)
Fiscal Year 2002: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2001: ¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2000: ¥2,700,000 (Direct Cost: ¥2,700,000)
|Keywords||VLFS / submersed plate / reduction effect of oscillation / elastic deflection / modal analysis / eigenmode / breaking wave phenomenon / negative added mass / 流体力相互干渉 / 流体力の増加 / ドライ固有モード / 大型浮体構造物 / 付加質量の増加 / 減衰力の増加 / 波数分裂 / 消波効果 / 高次流体力成分 / MAC法|
We have proposed a new very large floating structure with a submerged plate for the purpose of developing a very large floating structure (VLFS) with a conventional breakwater system, and have performed the following studies.
1. We have developed the numerical computing program for estimating the hydrodynamic forces on the submerge plate and the fore part of the very large floating structure with the submerged plate, and have performed the experimental studies. The following conclusions are obtained.
(1) The breaking waves are generated on the submerged-plate in short wave periods, and it dissipates the incident wave energy. As a result, all of the wave exciting forces on the fore part of VLFS are decreasing.
(2) The added mass on the submerged-plate oscillating near VLFS is slightly larger than the one on the submerged plate only for all oscillation frequencies, while the damping forces coefficients increase with the oscillation frequencies. Thereby, it has been made clear that the incre
ase of the total hydrodynamic forces on submerged plate is induced by the increase of damping force in the high frequency range.
(3) The added mass on the submerged plate takes the negative value in the long oscillation periods, and the damping force coefficients increase at the same time. Therefore, the characteristics of these hydrodynamic forces are useful for reducing the elastic deflection of VLFS in long wave periods.
2. We have applied the modal analysis method to the elastic deflection of VLFS, and have made clear the effect of the submerged plate on the elastic deflection of VLFS in waves. The following new information is obtained in this study.
(1) The wave exciting forces rather than the radiation forces strongly affect the reduction of the elastic deflection of VLFS.
(2) The submerged plate strongly affects on the wave exciting forces rather than the radiation forces. In particular, the submerged plate is useful for reducing the elastic deflection of VLFS for short wave periods.
(3) The submerged plate strongly affects the hydrodynaraic forces with the mode of less than the 8th, and it scarcely affect the ones with the higher modes.
From the above studies, we are sure that the proposed method is useful is useful for reducing the elastic deflection of VLFS in waves. Less