One-Dimensional Numerical Modelling of Mobile Bed Evolution in a Flume with a Side Weir

Abstract

Side weirs are widely used to control flow processes along a channel or river. The lateral loss of water reduces the sediment transport capacity in the main-channel leading to local sediment deposition near the overflow. The design discharge to be diverted is increased in an uncontrolled way by this flow-sediment interaction. The flow-sediment interaction is investigated numerically and compared with results from a flume study. The numerical tool is based on the continuity and momentum equations and performs the coupled hydrodynamic simulation of 1D flow behaviour and bed-load transport. The friction head loss is computed according to the Manning formula. The outflow is determined by applying the general equation of weirs. With an appropriate formula for bed-load transport capacity and an adequate roughness function to account for form roughness, the geometry of the sedimentary deposit, as well as the side overflow discharge, is reproduced with reasonable accuracy.

Numerical assessment of hydro‐morphodynamics affected by altered upstream discharge in the Dujiangyan reach of the Min River, China

“…Consequently, numerical simulation has emerged as the preferred approach for investigating the complex hydrodynamics, bedload transport and morphodynamics of large rivers (Liu et al, 2020; Luo et al, 2018; Zheng et al, 2020). 1D numerical models are appealing because of their high computational efficiency and minimal basic data requirements, but applications are comparatively restricted and unsuitable for complex configurations because of model reliance on limited information (Dou et al, 2017; Nistoran et al, 2017; Rosier et al, 2014). Conversely, 3D models have gained widespread acceptance for modelling laboratory‐controlled flume flows and local‐scale scour (such as that occurring at bridge piers), owing to their ability to capture secondary flow patterns driven by external forces or internal turbulence anisotropy (Epely‐Chauvin et al, 2015; Omara et al, 2018; Quezada et al, 2018).…”

Semi-empirical model for channel bed evolution due to lateral discharge withdrawal

“…There, the disturbance of the equilibrium between bed-load transport capacity of the main channel and sediment supply reaches its maximum. This location can be considered to be conservative, since the side overflow discharge Q D is larger than for a deposit located upstream of the downstream weir corner (Rosier et al 2009a).…”