EXPERIMENTAL ASSESSMENT OF SUSPENDED SEDIMENT CONCENTRATION CHANGED BY SOLITARY WAVE

Abstract

A large scale solitary wave causes a lot of sediment transportation and coastal beach erosion, for example tsunami is the one type of solitary waves. During passing such solitary wave over coastal region, higher energy on sediment transportation near bottom would bring to massive geomorphological changes and even worse damages in life and economics. The major objective of this study is to analyze the incipient motion of sediment suspended from bottom by a solitary wave through hydraulic experiments and numerical simulations. First, to estimate the process of sediment transport the experimental study was carried out in the prismatic rectangular channel of 12 min length, 0.8 m in width and 0.75 m in height. Solitary waves were generated by an abrupt opening of a sluice gate upstream for several water depth conditions. Two different types of sediments were used: Joomoonjin sand (d(50) = 0.58 mm, SG = 2.65) and anthracite (d(50) = 1.55 mm, SG = 1.61). Before starting each experiment, sediments were laid out with the thickness of 0.3 m on the slope of 1/6. During each experiment, turbidities were measured by sampling suspended sediment concentrations at 5 collecting points, which were used to calibrate the numerical simulations. Numerical simulations using the FLOW-3D with the GMO (General Moving Object) module were performed to investigate the relationship between turbulence intensity and suspended sediment concentration (SSC) after the validation with experiment results. It was found that SSC was mainly affected by the wave height and run-up/down velocity along a slope for a solitary wave passage. Turbulence intensity was considered as the most effective factor to comprehend the overall pattern of SSC distributions when turbulence of solitary wave was analyzed through the regression analysis. Finally, each non-dimensional empirical formula was suggested to estimate SSC occurred by a solitary wave passage for plunging and spilling break types, respectively. Moreover, results from this study would provide fundamental assessment to bridge between solitary wave characteristics and SSC based on laboratory experiments and numerical simulations.