1992 Fiscal Year Final Research Report Summary
Generation Mechanism of Infra-gravity waves on coral reef coasts
| Project/Area Number |
03452214
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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 | UNIVERSITY OF THE RYUKYUUS |
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Principal Investigator |
NAKAYAMA Eizo Ryukyuu Univ., Engineering, Civil Engineering, Research Associate, 工学部, 助手 (90180265)
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| Co-Investigator(Kenkyū-buntansha) |
TSUTSUI Sigeki Ryukyuu Univ., Engineering, Civil Engineering, Associate Professor, 工学部, 助教授 (10035644)
TSUKAYAMA Seikho Ryukyuu Univ., Engineering, Civil Engineering, Professor, 工学部, 教授 (50044996)
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| Project Period (FY) |
1991 – 1992
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| Keywords | surf beat / edge waves / infra-gravity waves / wave-induced currents / corral reef coasts / wave grouping / wave breaking / radiation stress |
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| Research Abstract |
Systematic measurements, to clarify the generating mechanism of infra-gravity waves, have been performed during the Typhoon T9119 was coming to Okinawa Islands of Japan. The significant wave height of incident waves exceed 10m-heigh. From the observed data, the periods of the infra-gravity waves are selectly at inherent periods which are the eigenvalues of sea surface oscillations. Surf beats are resonantly excited on coral reef areas by incoming wave groups. There are two kind of longperiod waves offshore the reef edge, one is the forced waves incoming with the wave groups, other is the free out-going waves from the reef areas. The height of the ifra-gravity waves are significantly correlated with the significant height of incident waves, than the other characteristic parameters of incident wave groups. The long wave height has a quadratic relation with the incoming wave height.
To estimate wave height distributions of the long waves and the short period waves on coasts with the coral reef and having the line of bathymetric discontinuity, numelical simulation methods are ne*ly developed. Concerning with the wave height, the simulation results are good agreement with the observed ones.
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