Approximate velocity formula over mobile sediment bed induced by velocity-skewed waves and current |
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| Authors: | Xin Chen Minghong Chen Jingkai Wu Haifei Liu Chen Yang |
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| Institution: | 1. Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System, China Agricultural University, Beijing 100083, China;2. State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China;3. China Huadian Corporation, Beijing 100031, China;4. School of Environment, Beijing Normal University, Beijing 100875, China;5. School of Water Conservancy, North China University of Water Resources and Electric Power, Zhengzhou 450045, China |
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| Abstract: | A velocity formula is proposed for flow over a mobile sediment bed induced by velocity-skewed waves and current.The formula is obtained by a separation of waves and current velocities and requires seven free variables related to free stream velocity and sediment characteristics.The formula includes two parts:(1) a wave part consisting of the free stream velocity and defect function,which considers phase lead,wave boundary layer thickness,and mobile bed level,and (2) a current part,which changes the wave part through the boundary layer thickness and mobile bed level,influenced by wave eddy viscosity.The wave part is superior to the current part such that the boundary layer characteristics are mainly determined by the waves.The wave process is divided into four quarter stages to model the asymmetries of parameters in velocity and acceleration.Under velocity-skewed waves and current conditions,velocity asymmetry and residual velocity are accounted for in the formula,especially the offshore residual ve-locity with a large phase lag and mobile bed effect with a small phase lag.Phase lead is shown to be non-constant in velocity-skewed oscillatory sheet flow and corresponds to an extra offshore residual velocity. |
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| Keywords: | Analytical approximate velocity Mobile sediment bed Sediment transport Velocity asymmetry Wave and current |
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