1996 Fiscal Year Final Research Report Summary
Evaluation of sediment transport under waves and currents
| Project/Area Number |
07650590
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | Yokohama National University |
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Principal Investigator |
SHIBAYAMA Tomoya Yokohama National University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (40143391)
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| Co-Investigator(Kenkyū-buntansha) |
OKAYASU Akio Yokohama National University, Graduate School of Engineering, Associate Professo, 工学研究科, 助教授 (20213994)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Sediment / Surfzone / Waves / Currents |
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| Research Abstract |
A numerical model is developed to predict bottom topography changes around river mouth. The wave field is calculated by using mild slope equation with including wave-current interaction effect. Near-bottom velocity variations and the distribution of radiation stress are evaluated by using the calculated wave field. The current field associated with sand movement is calculated including wave induced current and river discharge. The river current is introduced into the model as a boundary condition. Since we included wave-current interaction, it was necessary to calculate by iteration process in order to get converged solutions for wave and current field.
Bed load transport rate is calculated from bottom shear stress caused by wave orbital motion, wave induced nearshore current and river current. Suspended sand discharge from the river and suspended sand due to wave breaking are also included in the model. The wave field, current field and bottom topography changes are compared with labor
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atory results in order to examine the accuracy of numerical model.
Laboratory experiments are performed in a wave basin designed to facilitate the understanding of the mechanism of sand movement as well as the behavior of wave and current field around river mouth. Well-sorted sand (median diameter 0.15mm) are laid in the wave basin to make an 2.5 times 2.3 meter test bed with the initial slope of 1/20. A river mouth with water discharge was installed at upper end of the test bed. The distribution of wave height and the variation of near-bottom velocities in the test section are measured in details by using capacitant wave gages or an ultra-sonic velocity meter respectively for three conditions of monochromatic waves and river discharges.
From comparisons, we can judge that the present numerical model, which includes wave-current interaction, bed load and suspended load due to wave breaking and river discharge, can predict laboratory results of beach changes in the vicinity of river mouth areas. Less
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