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http://dx.doi.org/10.9765/KSCOE.2013.25.6.374

Sediment Particulate Motions Over a Ripple Under Different Wave Amplitude Conditions  

Chang, Yeon S. (Miami Dade College, Ocean Circulation and Climate Change Research Department, Korean Institute of Ocean Science and Technology)
Ahn, Kyungmo (School of Spatial Environment System Engineering, Handong Global University)
Hwang, Jin H. (Department of Civil & Environmental Engineering, Seoul National University)
Park, Young-Gyu (Ocean Circulation and Climate Change Research Department, Korean Institute of Ocean Science and Technology)
Publication Information
Journal of Korean Society of Coastal and Ocean Engineers / v.25, no.6, 2013 , pp. 374-385 More about this Journal
Abstract
Sediment particle motions have been numerically simulated over a sinusoidal ripple. Turbulent boundary layer flows are generated by Large Eddy Simulation, and the sediment particle motions are simulated using Lagrangian particle tracking method. Two unsteady flow conditions are used in the experiment by employing two different wave amplitudes while keeping other conditions such as wave period same. As expected, the amount of suspended sediment particles is clearly dependent on the wave amplitude as it is increasing with increasing flow intensity. However, it is also observed that the pattern of suspension may be different as well due to the only different condition caused by wave amplitude. Specially, the time of maximum sediment suspension within the wave period is not coincident between the two cases because sediment suspension is strongly affected by the existence of turbulent eddies that are formed at different times over the ripple between the two cases as well. The role of these turbulent eddies on sediment suspension is important as it is also confirmed in previous researches. However, it is also found the time of these eddies' formation may also dependent on the wave amplitude over rippled beds. Therefore, it has been proved that various flow as well as geometric conditions under waves has to be considered in order to have better understanding on the sediment suspension process over ripples. In addition, it is found that high turbulent energy and strong upward flow velocities occur during the time of eddy formation, which also supports high suspension rate at these time steps. The results indicate that the relationship between the structure of flows and bedforms has to be carefully examined in studying sediment suspension at coastal regions.
Keywords
sediment particle motion; large eddy simulation(LES); wave amplitude; suspended sediment; turbulence;
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