A sheetflow sediment transport model for skewed-asymmetric waves combined with strong opposite currents |
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| Institution: | 1. Department of Civil Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo ku, Tokyo 113-8656, Japan;2. Department of Ocean Science and Engineering, Zhejiang University, 866 Yuhangtang Road, Hangzhou, Zhejiang, 310058, China;1. Dept of Clinical Therapeutics, University of Athens, Athens, Greece;2. Hellenic Genito-Urinary Cancer Group (HGUCG);3. Second Urology Department, University of Athens, Athens, Greece;4. Dept of General Medical Oncology and Laboratory for Experimental Oncology, University Hospitals Leuven, Leuven Cancer Institute, Leuven, Belgium;5. Hôpital Européen Georges Pompidou;6. Institute Gustav Roussy;7. First Urology Department, University of Athens, Athens, Greece;8. Department of Hygiene, Epidemiology and Medical Statistics, University of Athens, Athens, Greece;1. Professor, Department of Civil Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan;2. Ministry of Land, Infrastructure, Transport and Tourism, Japan;3. Researcher, Department of Civil Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan |
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| Abstract: | Prototype scale physical model tests were conducted to investigate the sheetflow sediment transport of uniform sand under different skewed-asymmetric oscillatory flows with and without the presence of relatively strong currents in the opposite direction against wave propagation. Experiments show that in most cases with fine sands, the “cancelling effect” which balances the on-/off-shore net transport under pure asymmetric/skewed oscillatory flows and results a moderate net transport was developed for combined skewed-asymmetric shaped oscillations. However, under certain conditions (T > 5 s) with coarse sands, the onshore sediment transport was enhanced for combined skewed-asymmetric flows. Additionally, the new experimental data under collinear oscillatory flows and strong currents show that offshore net transport rates increase with decreasing velocity skewness and acceleration skewness. Sediment movement behaviors were investigated through analysis of experimental data obtained from the image analysis technique and attempts were made to estimate and formulate the sheetflow layer thickness. Accordingly, sediment transport under oscillatory sheetflow conditions was studied and successfully explained by comparing the bed shear stress and the phase lag parameter at each half cycle. Consequently, these parameters were incorporated in an improved Dibajinia and Watanabe's type sediment transport model. The formula is calibrated against a comprehensive experimental data (331 in total). Good agreement obtained between predictions and measurements shows that the new formula is fulfilled for practical purposes. |
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