High-precision sediment flux measurement and integrated sediment transport evaluation in swash zone

2016 Fiscal Year Final Research Report

• Project/Area Number: 26289161
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Hydraulic engineering
• Research Institution: Tokyo University of Marine Science and Technology
• Principal Investigator: Okayasu Akio 東京海洋大学, 学術研究院, 教授 (20213994)
• Co-Investigator(Kenkyū-buntansha): 下園 武範 東京大学, 工学(系)研究科(研究院), 准教授 (70452042)
• Research Collaborator: FENG Dejun ; WU Lianhui
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 遡上帯 / 漂砂 / 底質移動フラックス / 画像流速計測 / 透過型濃度計 / 段波砕波

Outline of Final Research Achievements

A wide-range high-precision image-based measurement system with a planer backlight and dual stroboscopic lamps for simultaneous measurement of 2-D sediment concentration and sediment transport velocity was developed. Detailed investigations of flow velocity and sediment flux of swash events on a dry bed were performed and the following results were obtained. 1) Boundary layer thickness increases at the early stage of run-up, decreases at the flow reversal phase and increases again at the backwash, 2) turbulence intensity at the run-up phase can be twice that at the time of backwash, turbulence near the bottom is dominant at the toe of swash, 3) the peak of onshore directed sediment flux is significantly larger than that for the offshore direction, and the conventional sediment transport models cannot evaluate sediment transport flux well at the early phase and the final phase of the swash events due to strong turbulence and non-equilibrium state of concentration.

Free Research Field

海岸工学