Abstract
In this paper, we investigate the performance of three-dimensional (3D) hydraulic modeling when dealing with river sinuosity and meander bends. In river bends, the flow is dominated by a secondary current, which has a key role on the flow redistribution. The secondary flow induces transverse components of the bed shear stress and increases the velocity in outward direction, thus generating local erosion and riverbed modifications. When in river bends, the 3D processes prevail, and a 3D computational fluid dynamics (CFD) model is required to correctly predict the flow structure. An accurate description of the different hydrodynamic processes in mildly and sharply curved bends find a relevant application in meanders migration modeling. The mechanisms that drive the velocity redistribution in meandering channels depend on the river’s roughness, the flow depth (H), the radius curvature (R), the width (B) and the bathymetric variations. Here, the hydro-geomorphic characterization of sharp and mild meanders is performed by means of the ratios R/B, B/H, and R/H, and of the sinuosity index. As a case study, we selected the Malpasset dam break on the Reyran River Valley (FR), as it is perfectly suited for investigating performances and issues of a 3D model in simulating the inundation dynamics in a river channel with a varying curvature radius.
Highlights
The detailed study of hydraulic processes in sharply-curved bends is of practical relevance [1] as the water flow and sediment transport generate local erosion resulting in bed changing and impacting infrastructures
This paper presents a fully 3D model of the flow field in a river channel characterized by different bending, ranging from mild to sharp
The water stage values in almost rectilinear reaches could even be predicted by a 1D model, as observed by Howard [7] and by Di Francesco et al [61]
Summary
The detailed study of hydraulic processes in sharply-curved bends is of practical relevance [1] as the water flow and sediment transport generate local erosion resulting in bed changing and impacting infrastructures. The flow field in river bends is highly three-dimensional [5,6], being characterized by secondary flows that cause high bank shear stress and erosion of the outer part of the bend. Cut-off events, representing the driving mechanism of long-term and large-scale meander morphologic dynamics, typically occur in sharply-curved bends [7]. Meandering rivers represent fluvial geometric settings where three-dimensional (3D) models have a high performance because of the complex characterization of the flow [5]. This paper deals with the investigation of the hydraulic processes governing the velocity redistribution and water surface elevation in sharply-curved open-channel bends by means of a detailed 3D numerical simulation. The selected case study is the Malpasset dam break [8] characterized
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
