2001 Fiscal Year Final Research Report Summary
Study on Three-Dimensional Beach Deformation Model for Nonlinear Multi-Directional Random Waves
| Project/Area Number |
11450186
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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 | 一般 |
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| Research Field |
水工水理学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
WATANABE Akira Graduate School of Engineering, The University of Tokyo, Professor, 大学院・工学系研究科, 教授 (80011138)
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| Co-Investigator(Kenkyū-buntansha) |
SASAKI Jun Graduate School of Frontier Sciences, The University of Tokyo, Associate Professor, 大学院・新領域創成科学研究科, 助教授 (50292884)
SATO Shinji Graduate School of Engineering, The University of Tokyo, Professor, 大学院・工学系研究科, 教授 (90170753)
ISOBE Masahiko Graduate School of Frontier Sciences, The University of Tokyo, Professor, 大学院・新領域創成科学研究科, 教授 (20114374)
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| Project Period (FY) |
1999 – 2001
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| Keywords | Multi-directional random waves / Beach deformation / Sand transport rate formula / Wave breaking model / Swash zone / Numerical model / Multi-directional random wave basin / Nonlinear mild slope equation |
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| Research Abstract |
The objective of the present study is to develop an accurate and practical numerical model for three-dimensional beach evolution under nonlinear multi-directional random waves. Nonlinear mild slope equations proposed by Isobe (1994) were adopted as a wave-current model and modified with respect to wave breaking by formulating a breaker-induced energy dissipation term, in which the breaking point can be automatically determined. For the breaking criterion on multi-directional random waves, a prototype of breaking index was proposed by introducing specific parameters for multi-directionality and frequency-wise irregularity. The nearshore boundary condition was also improved to include swash zone dynamics under multi-directional random waves.
The extended Boussinesq-type equations derived by Nwogu (1993) were modified for applications to nearshore waves and currents including surf and swash zones. For a sand transport model, the sheet flow transport rate formula proposed by Dibajnia and Watanabe (1997) was used as a basis, which can determine the net sand transport rate using a set of asymmetric oscillatory flow velocities. The formula was extended to general horizontal plane problems where waves and currents were in the different directions. After predicting the net sand transport rate, the conservation equation of sediment mass was solved to determine the topographic change. The validity of the model was confirmed through comparisons with laboratory data on waves, currents and beach deformation around coastal structures under multi-directional irregular waves.
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