2001 Fiscal Year Final Research Report Summary
REPRODUCTION OF REAL SEA STATE DURING A STORM BY MULTI-DIRECTIONAL WAVE-MAKERS
| Project/Area Number |
10555173
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
水工水理学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
TAKAYAMA Tomotsuka Kyoto university, Disaster Prevention Research Institute, Professor, 防災研究所, 教授 (60273520)
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| Co-Investigator(Kenkyū-buntansha) |
SATOH Shinji University of Tokyo, Graduate School of Civil Eng., Dept. of Civil Eng., Professor, 大学院・工学研究科, 教授 (90170753)
HIRAISHI Tetsuya Ind. Adm. Institution, Port and Airport Research Institute, Chief of Wave Lab., (研究職)波浪研究室長
MASE Hajime Kyoto university, Disaster Prevention Research Institute, Associate Professor, 防災研究所, 助教授 (30127138)
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| Project Period (FY) |
1998 – 2000
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| Keywords | Stormy waves / Statistics of storm waves / Wave Transformation / Unsteady wave generation / Uni-directional waves / Directional spectrum |
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| Research Abstract |
Wind waves are rapidly developed as a storm grows up from a calm state, and they reach to maximum at the strongest state of the storm. As the storm decays and returns to the original calm state, the waves gradually decrease. Thus, the height, period and direction of the waves vary during a storm. Though presently available wave-makers can generate directional random waves in a steady state, they cannot generate the waves in an unsteady state like a storm. Therefore, it is very important to develop the reproduction model of unsteady random waves in a laboratory.
It is necessary to obtain sufficient information about the characteristics of sea waves in order to reproduce stormy wave in a laboratory. The wave observation stations at Wajima in Japan Sea and at Omaezaki in the Pacific were selected. The time historical variations of observed waves during a storm have been characterized to introduce them into the reproduction model. The waves more than 2m are defined as stormy waves and their
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duration time and variation rates in increase and decrease of the storm waves have been investigated. Though the occurrence rates of the storm duration at the two stations decreases exponentially the occurrence rate of long duration at Wajima is higher than that at Omaezaki. Especially at Omaezaki, the appearance rate of multi-peaked spectra was also checked The effect of external waves on the waves inside a bay during a storm has been investigated numerically for Osaka Bay. Though the external waves are relatively influential on small waves inside the bay, they become negligible for large waves developed inside the bay.
Taking into account the characteristics of observed waves in fields, reproduction model of unidirectional random waves during a storm has been developed for a wave flume. It has been confirmed that unsteady random waves generated in the flume well agree with the target waves observed in a storm. A reproduction model of directional random waves in a storm has been proposed, but the model could not directly be introduced into the present procedures of directional wave-makers. Therefore, it is impossible to evaluate the proposed model by reproducing directional random storm waves in a laboratory. The evaluation of the model in hydraulic experiments is a future subject to solve. Less
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