| Project/Area Number |
01460184
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Hydraulic engineering
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| Research Institution | Osaka University |
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Principal Investigator |
SAWARAGI Toru Osaka Univ. Civil Eng. Professor, 工学部, 教授 (60028975)
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| Co-Investigator(Kenkyū-buntansha) |
ONO Masanobu Osaka Univ. Civil Eng. Research Associate, 工学部, 助手 (80214188)
AOKI Shinichi Osaka Univ. Civil Eng. Research Associate, 工学部, 助手 (60159283)
NOCHINO Masao Osaka Inst. of Tech. Civil Eng. Assistant Prof., 講師 (10116080)
DEGUCHI Ichiro Osaka Univ. Civil Eng. Associate Professor, 工学部, 助教授 (00029323)
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| Project Period (FY) |
1989 – 1990
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| Project Status |
Completed (Fiscal Year 1990)
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| Budget Amount *help |
¥3,900,000 (Direct Cost: ¥3,900,000)
Fiscal Year 1990: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1989: ¥3,200,000 (Direct Cost: ¥3,200,000)
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| Keywords | Offshore Structure / Wave Grouping / Rubble Mound Breakwater / Long Wave / Sand Drift / Longshore Current / Run / Moored Vessel / グル-ピング特性 / 長周期水位変動 / 不規則波 / 群波 / 波変形 / 浮遊式海洋構造物 |
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| Research Abstract |
Sawaragi carried out a series of experiments to investigate the effect of grouping on the stability of rubble mound breakwater. It is found that the critical condition of stability is closely related to the runs of wave height and surf similarity parameter together with the run-length of incident wave energy. A new design formula for the rubble mound breakwater is proposed based on the expected damage rate where the initial slope of the rubble mound and the effect of frictional resistance of rubbles are taken into account. Deguchi and Nochino investigated the characteristics of grouping of measーured wind waves in the fields. Any significant relation can not be found between parameters which represent the property of grouping (eg. run-length or groupiness factor) and those which express the characteristics of the frequency spectrum (eg. peakedness or band-width parameter). However, the probability distribution of wave height became flatter than Rayleigh distribution when waves indicate strongly grouping property. Further, although groupiness become weak in the surf zone, amplitudes of bounded long wave increase toward shoreline which cause low frequency fluctuation in longshore current and mean water surface. Aoki investigated characteristics of oscillation at the grouping frequency in the two oscillation systems, that is, an oscillation of a floating vessel and surface oscillation in a rectangular bay. It is found that the oscillation of rectangular vessel becomes large when the grouping frequency is the same as the natural frequency of the moored vessel. Ono studied the differences of suspended sediment caused by irregular waves and regular waves through experiments and found that the irregular waves have higher diffusivities than the regular waves.
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