Author(s): Takayuki Tanaka; Ryuki Harata; Syun Tsutsui

Linked Author(s): Takayuki Tanaka

Keywords: Flood levee failure; Flow mechanism; River bends; Fluid numerical simulation; PIV

Abstract: Due to the effects of climate change, river flood damage caused by storms is occurring worldwide. Especially in Japan, levee breaks and floods occur frequently due to large typhoons and torrential rains, resulting in devastating damage throughout the country. Although research on the flow for breakwaters and bends has been conducted, there has been no research on the dike model using earthen levee. Therefore, in this study, we examined the situation of levee breakage when a levee model was installed around the curved part of the river channel, mainly for earthy levee with a lot of sand. Furthermore, the flow mechanism in the non-overflow state was investigated by experiments and numerical analysis. The experiment was carried out by installing the embankment model on a model stand with a total length of 180 cm and a width of 90 cm. The material of the embankment model used for the embankment experiment was a 2:1 mixture of silica sand and Fujimori clay. After creating a levee model with a river width of 20 cm, a levee height of 10 cm, a radius of curvature of a curved part of 60 cm, and a tangential angle of 60 degrees, water with a flow rate of 2 liters/s is flowed to examine the breach location and a video camera is used. The surface flow was analyzed by the existing PIV method. A model experiment using a clay embankment revealed that embankment is likely to occur from the straight part to the outer bank side of the curved part inflow part in the non-overflow state. In addition, it was clarified that the breach is likely to occur on the inner bank side of the straight part on the inner bank side and the curved inflow part in the overflow state. Furthermore, analysis of the surface flow condition by experiments and numerical simulations revealed that the flow velocity on the left bank side increases as the flow velocity flows from the straight part to the curved part. In addition, the surface flow condition in the model experiment could be reproduced to some extent by numerical analysis, such as the fact that the flow velocity on the right bank side near the inflow from the curved part to the straight part showed a small value.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022105

Year: 2022