Sediment Particulate Motions Over a Ripple Under Different Wave Amplitude Conditions
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초록
Sediment particle motions have been numerically simulated over a sinusoidal ripple. Turbulent boundarylayer flows are generated by Large Eddy Simulation, and the sediment particle motions are simulated usingLagrangian particle tracking method. Two unsteady flow conditions are used in the experiment by employing twodifferent wave amplitudes while keeping other conditions such as wave period same. As expected, the amount ofsuspended sediment particles is clearly dependent on the wave amplitude as it is increasing with increasing flowintensity. However, it is also observed that the pattern of suspension may be different as well due to the onlydifferent condition caused by wave amplitude. Specially, the time of maximum sediment suspension within the waveperiod is not coincident between the two cases because sediment suspension is strongly affected by the existence ofturbulent eddies that are formed at different times over the ripple between the two cases as well. The role of theseturbulent eddies on sediment suspension is important as it is also confirmed in previous researches. However, it isalso 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 inorder to have better understanding on the sediment suspension process over ripples. In addition, it is found that highturbulent energy and strong upward flow velocities occur during the time of eddy formation, which also supportshigh suspension rate at these time steps. The results indicate that the relationship between the structure of flows andbedforms has to be carefully examined in studying sediment suspension at coastal regions.
Abstract
Sediment particle motions have been numerically simulated over a sinusoidal ripple. Turbulent boundarylayer flows are generated by Large Eddy Simulation, and the sediment particle motions are simulated usingLagrangian particle tracking method. Two unsteady flow conditions are used in the experiment by employing twodifferent wave amplitudes while keeping other conditions such as wave period same. As expected, the amount ofsuspended sediment particles is clearly dependent on the wave amplitude as it is increasing with increasing flowintensity. However, it is also observed that the pattern of suspension may be different as well due to the onlydifferent condition caused by wave amplitude. Specially, the time of maximum sediment suspension within the waveperiod is not coincident between the two cases because sediment suspension is strongly affected by the existence ofturbulent eddies that are formed at different times over the ripple between the two cases as well. The role of theseturbulent eddies on sediment suspension is important as it is also confirmed in previous researches. However, it isalso 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 inorder to have better understanding on the sediment suspension process over ripples. In addition, it is found that highturbulent energy and strong upward flow velocities occur during the time of eddy formation, which also supportshigh suspension rate at these time steps. The results indicate that the relationship between the structure of flows andbedforms has to be carefully examined in studying sediment suspension at coastal regions.
참고문헌 (28)
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