Author(s): Qiyun Pang; Shinichiro Onda

Linked Author(s): QIYUN PANG, Shinichiro Onda

Keywords: Numerical simulation; Lateral overtopping flows

Abstract: In recent years, unexpected heavy rains were frequently reported across the world. In late June through mid-July 2018, Typhoon No.7 which brought successive heavy downpours landed in southwestern Japan and resulted in catastrophic floods. In this flood event, levee breaching due to overtopping flows occurred and caused severe damage in landside domain. On the other hand, as a flood control measurement, lateral overflow weir (relief channel) aims to relieve flood risks by leading flood flows that exceed the capacity of river channels and drainage channels to a reservoir. To predict overflow at lateral weir and flows and bed deformation in levee breaching process, it is of great importance to develop a numerical model to simulate overtopping flows and sediment transport accurately around such a structure. Nevertheless, the detailed mechanism of overflow phenomena in curved or meandering channels is not still very clear. Because overtopping side weir may be installed not only in a straight channel but also in the meandering part, which depends on topographical and social conditions. Moreover, there are few studies about lateral overtopping flows in these curved channels. For this reason, a numerical analysis is indispensable to simulate accurately water surface and velocity distribution in overflows. The purpose of this research is to develop a three-dimensional numerical model to simulate lateral overflow phenomena and predict hydraulic characteristics accurately. In this research, to apply the lateral overtopping flows in a curved channel, curvilinear coordinate system is adopted for this 3D RANS model. And the density function method is performed to capture water surface fluctuations in unsteady flows As a first step, the characteristics of a laboratory-scale lateral overtopping flow in a straight channel are investigated as a verification of feasibility of this 3D model. Water surface profile, velocity distribution and overflow rate were compared with experiments and reasonable results have been acquired and confirmed in the first stage. In the next step, lateral overtopping flows at a channel bend will be simulated and also be compared with experiments to verify if this model can precisely simulate a sophisticated phenomenon of lateral overflow, which including water surface profile, secondary flow in meandering channel, and so on.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022994

Year: 2022