Comparative 1D and 3D numerical investigation of open-channel junction flows and energy losses

Luo, Hao; Fytanidis, Dimitrios K.; Schmidt, Arthur; García, Marcelo H.

doi:10.1016/j.advwatres.2018.05.012

Cited by 70 publications

(36 citation statements)

References 35 publications

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“…A significant fraction of water is expected to flow through the shorter paths linking the upstream to the downstream part of the flume (red solid lines in Fig.12); along these lines, the mean free-surface gradient is in fact the largest. However, both these paths are characterized by narrow branches (those aligned with the T direction) and by 90°bends, which are known to cause significant head losses (Arrault et al, 2016;El Kadi Abderrezzak et al, 2011;Luo et al, 2018;Mignot et al, 2008;Rivière et al, 2011Rivière et al, , 2014Weber et al, 2001). Hence, most of the water flows along the wider streets, i.e., along the L principal direction (Fig.…”

Section: Comparison With Laboratory Experiments Under Steady Flow Condmentioning

confidence: 99%

Modelling urban floods using a finite element staggered scheme with an anisotropic dual porosity model

Viero

2019

Journal of Hydrology

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In porosity models for urban flooding, artificial porosity is used as a statistical descriptor of the urban medium. Buildings are treated as subgrid-scale features and, even with the use of relatively coarse grids, their effects on the flow are accounted for. Porosity models are attractive for large-scale applications due to limited computational demand with respect to solving the classical Shallow Water Equations on high-resolution grids. In the last decade, effective schemes have been developed that allowed accounting for a wealth of sub-grid processes; unfortunately, they are known to suffer from oversensitivity to mesh design in the case of anisotropic porosity fields, which are typical of urban layouts. In the present study, a dual porosity approach is implemented into a two-dimensional Finite Element numerical scheme that uses a staggered unstructured mesh. The presence of buildings is modelled using an isotropic porosity in the continuity equation, to account for the reduced water storage, and a tensor formulation for conveyance porosity in the momentum equations, to account for anisotropy and effective flow velocity. The element-by-element definition of porosities, and the use of a staggered grid in which triangular cells convey fluxes and continuity is balanced at grid nodes, allow avoiding undesired mesh-dependency. Tested against refined numerical solutions and data from a laboratory experiment, the model provided satisfactory results. Model limitations are discussed in view of applications to more complex, real urban layouts.

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Section: Comparison With Laboratory Experiments Under Steady Flow Condmentioning

confidence: 99%

Modelling urban floods using a finite element staggered scheme with an anisotropic dual porosity model

Viero

2019

Journal of Hydrology

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“…(2002) and Luo et al. (2018) (see supporting information). This analysis reveals the fundamental role of the parameter K I , as a value of at least 0.1 is needed to obtain the same qualitative behavior depicted in Figure 6, where the confluence tilts toward the dominant channel (i.e., that carrying more water and sediment).…”

Section: Resultsmentioning

confidence: 83%

“…Similarly, in Figure 7b, we explore the role of different values of the interfacial shear coefficient, from the extreme case K I = 0 (hence, neglecting the effect of the interfacial shear term in the momentum balance) to the more realistic values of 0.2-0.3 reported by Shabayek et al (2002) and Luo et al (2018) (see supporting information). This analysis reveals the fundamental role of the parameter K I , as a value of at least 0.1 is needed to obtain the same qualitative behavior depicted in Figure 6, where the confluence tilts toward the dominant channel (i.e., that carrying more water and sediment).…”

Section: (A) (B)mentioning

confidence: 99%

Coupled Morphodynamics of River Bifurcations and Confluences

Ragno

Redolfi

Tubino

2021

Water Resources Research

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The study of multithread systems like braided and anastomosing rivers, deltas, alluvial fans, represents a fascinating topic in the vast world of river patterns. The flow splits around exposed bars, islands, ridges, and often reconnects a little further downstream. Water and sediment partition in the bifurcates has a fundamental control of the river morphological evolution and ecological functionality (Ashmore, 2013; Nanson & Knighton, 1996). At the channel scale, bifurcations and confluences play the role of basic unit processes of multithread systems. Understanding their own distinct morphology, flow structure and dynamics, as well as their mutual interplay, is therefore of crucial importance for managing water resources, mitigating the impacts of anthropic pressure [e.g., dams construction (Graf, 2006; Tong-Huan et al., 2020)], ensuring flood protection and adopting river restoration measures suitable for recovering deteriorated ecosystems (e.g., Habersack & Piégay, 2007; Wohl et al., 2015). Almost all studies performed to date consider the two processes separately, although they frequently appear as closely interconnected. Figure 1 shows some illustrative examples of the morphological bond between bifurcations and confluences in different fluvial environments. Braided rivers like the Rakaia River in New Zealand (Figure 1a) are characterized by a complex, highly dynamic planform, where the water and sediment fluxes divide among multiple channels, although just few of them are morphologically active at a given time (Ashmore, 2001; Bertoldi et al., 2009a). In these fluvial systems, sequences of confluence-bifurcation units are ubiquitous features that control channel morphology and the spatial/temporal patterns of sediment transport (Ashmore, 2001; Ashworth, 1996). Midchannels bars and vegetated islands frequently recur in natural meandering rivers (Figure 1b), often associated with width fluctuations or chute and neck cutoff (Grenfell et al., 2012; Zolezzi et al., 2012). They also serve as key elements in the restoration of pristine multithread patterns, as in the case of the Drau River in Austria (Figure 1c), where a former side-channel was reopened with the aim of improving the habitat conditions, stabilize the river bed, and ensure flood protection through channel widening (

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“…Since none of the parameters controlling the frictional losses (R m , k s,m / h m , and h m /b m ) seems to explain the increase in the upscaled water depth for large distortion ratios, we hypothesize now that a competition with local losses (flow merging and separation at crossroads, hydraulic jumps, etc.) could be responsible for this result, as discussed hereafter (Luo et al, 2018).…”

Section: 1029/2019wr026774mentioning

confidence: 86%

Numerical Insights Into the Effects of Model Geometric Distortion in Laboratory Experiments of Urban Flooding

Erpicum

Mignot

et al. 2020

Water Resources Research

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Geometrically distorted scale models have been a valuable tool for physical modeling of urban flooding in a network of streets. However, little is known so far about the bias induced in such cases by the model geometric distortion. Here, we use 2‐D computational modeling to provide a first systematic quantification of this bias in the case of a synthetic urban layout. The bias is found to be generally small, with the maximum deviations of the upscaled flow depth and discharge partition from the corresponding values of the undistorted model being around 10% in the case of relatively rapid and shallow flow conditions. When the geometric distortion is increased, the computations reveal a nonmonotonous pattern of the flow variables (depth, discharge partition, and size of flow separation zones), which results from a competition between declining frictional losses and growing local losses in the model. These findings may guide the design of distorted scale models of urban flooding and assist the interpretation of laboratory observations for assessing flood protection measures, for process understanding or for validating computational modeling.

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Comparative 1D and 3D numerical investigation of open-channel junction flows and energy losses

Cited by 70 publications

References 35 publications

Modelling urban floods using a finite element staggered scheme with an anisotropic dual porosity model

Modelling urban floods using a finite element staggered scheme with an anisotropic dual porosity model

Coupled Morphodynamics of River Bifurcations and Confluences

Numerical Insights Into the Effects of Model Geometric Distortion in Laboratory Experiments of Urban Flooding

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