Impact of dissipation and dispersion terms on simulations of open-channel confluence flow using two-dimensional depth-averaged model

Yang, Qingyuan; Lu, Wen-Hsiang; Zhou, Su-fen; Wang, Xiekang

doi:10.1002/hyp.9881

Cited by 10 publications

(6 citation statements)

References 34 publications

(36 reference statements)

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“…Its popularity is dependent on the relatively smaller computational consumption compared with three‐dimensional (3D) numerical modelling and more importantly the computational robustness on significant variations of both hydrodynamics and morphology. 2D depth‐averaged modelling is still the most popular numerical method to simulate the morphological evolution of braided rivers, meanders, bifurcations and confluences (Guan et al, 2016; Kleinhans et al, 2006; Liu et al, 2020; Schuurman & Kleinhans, 2015; Wang et al, 2015; Xu et al, 2019; Yang et al, 2014). In this study, 2D numerical modelling is used to produce and investigate the hydro‐morphological processes of mountain river confluences despite its limitations due to 3D flow properties in the confluence region.…”

Section: Introductionmentioning

confidence: 99%

Numerical assessments of bed morphological evolution in mountain river confluences under effects of hydro‐morphological factors

Yan

Duan

Yang

et al. 2022

Hydrological Processes

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Understanding hydro‐morphological characteristics in mountain river confluences is significant in flood disaster mitigation and mountain river restoration, which is still poorly explored. This study employed a 2D hydro‐morphological model based on the finite element method to simulate the major bed morphological features in a mountainous‐type flume confluence and evaluate the effects of main controlling factors on these features. The modelling results show that the dominant bed morphological features in mountain river confluences can be well produced by the 2D model. Five controlling factors including downstream water level (H), branch discharge ratio (Qr), main channel sediment supply ratio (ψ), tributary slope (St) and confluence angle (α) reflecting different flow‐sediment‐geometry scenarios were adopted into a sensitive study. The upstream reach of the main channel is controlled by H and ψ and their decreases lead to bed degradation. The increase in Qr, St, and α mainly results in bed aggradation and steepening in the tributary, attaining a higher sediment transport rate. This contrasts the existing experimental results, due to the difference in sediment feeding. The size of the bank‐attached bar is promoted by the increase in Qr, St, and α and the decrease in H and ψ. A quantitative analysis shows that the water surface slope well correlates with various dimensions of the scour hole and bar morphology (correlation = 0.58–0.8). Meanwhile, the bank‐attached bar displays a strong self‐similarity (correlation = 0.84–0.98) regarding its geometric dimensions. This study provides new insights into the existing knowledge of the hydro‐sediment‐morphodynamics of mountain river confluences obtained from laboratory studies and field investigations.

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Section: Introductionmentioning

confidence: 99%

Numerical assessments of bed morphological evolution in mountain river confluences under effects of hydro‐morphological factors

Yan

Duan

Yang

et al. 2022

Hydrological Processes

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“…The hydro-sediment-morphodynamics of river confluences have been investigated for more than half a century. Field investigations (Rhoads and Sukhodolov, 2001;Sukhodolov and Rhoads, 2001;Biron et al, 2002;Riley and Rhoads, 2012;Ramón et al, 2013;Rhoads and Johnson, 2018;Zhang et al, 2020;Yuan et al, 2021), laboratory experiments (Taylor, 1944;Webber and Greated, 1966;Weber et al, 2001;Ribeiro et al, 2012;Yuan et al, 2018), and mathematical modelling studies (Bradbrook et al, 2001;Biron et al, 2004;Constantinescu et al, 2012;Lyubimova et al, 2014;Yang et al, 2014) have improved the understanding of the hydrodynamic characteristics, mixing, sediment transport, and bed morphology near river confluences. Generally, it has been revealed that the flow structure at river channel confluences can be divided into six major zones, i.e., flow stagnation, flow deflection, flow separation, maximum velocity, flow recovery, and distinct shear zones (Best, 1987).…”

Section: Introductionmentioning

confidence: 99%

Vertically layered flow structure at confluence of a reservoir and tributary carrying high sediment loads

Sun

Cao

et al. 2022

Front. Earth Sci.

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Enhanced understanding of flow structure at a river confluence is essential for predictions of sediment transport and morphological evolution. To date, however, the confluent flow structure of a reservoir and tributary carrying high sediment loads has remained poorly understood, and may be vertically layered sharply, featuring subaqueous sediment-laden flow, i.e., turbidity currents underneath subaerial clear water. Here a recently established 2D double layer-averaged model, able to resolve the formation, propagation, and recession of turbidity currents, is used to investigate a series of idealized laboratory-scale cases and a prototype case study of the Guxian Reservoir on the Yellow River, China. Four primary patterns of the stable, vertically layered flow structure at a reservoir-tributary confluence are identified: 1) single layers of sediment-laden inflow in both the main channel and tributary, sustained by sufficient vertical mixing; 2) a double layer in the main channel and a single layer of sediment-laden inflow in the tributary, when the sediment-laden flow in the tributary suffices to block intrusion of flow in the main channel; 3) a single layer of sediment-laden inflow in the main channel and a double layer in the tributary, induced by the intrusion of sediment-laden flow from the main channel into clear-water flow with small discharge in the tributary; and 4) double layers in both the main channel and tributary, which may be further divided into three subpatterns, as turbidity current exists in both the main channel and tributary, or in the main channel (tributary) intruding into the tributary (main channel). In response to unsteady discharge and sediment inputs from upstream, the vertically layered flow structure evolves in time, and may fall into one of the patterns identified above. Although bed deformation in the long term may modify the confluent flow, the vertically layered flow pattern remains so far as the present cases are concerned. The findings have implications for sediment transport and morphological evolution at a reservoir–tributary confluence, for which further studies are suggested to inform the optimization of reservoir operation schemes to mitigate capacity loss caused by sedimentation.

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“…The equations discretization use the Godunov method (Toro, 2001), which can capture the shock wave accurately and deal with the sharp change of bed form stably. The calculation time is acceptable, and is a very promising tool (Cao, et al, 2011;Yang, et al, 2014;Kvočka, et al, 2015;Yoshioka, et al, 2015;Guan, et al, 2016;Liang, et al, 2016;Hu and Song, 2018;Bellos, et al, 2020;Contreras and Escauriaza, 2020;Khosronejad, et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of a Flash Flood Process that Occurred in Zhongdu River, Sichuan, China

et al. 2021

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In 2018, a flash flood occurred in the Zhongdu river, which lies in Yibin, Sichuan province of China. The flood caused many casualties and significant damage to people living nearby. Due to the difficulty in predicting where and when flash floods will happen, it is nearly impossible to set up monitors in advance to detect the floods in detail. Field investigations are usually carried out to study the flood propagation and disaster-causing mechanism after the flood’s happening. The field studies take the relic left by the flash flood to deduce the peak level, peak discharge, bed erosion, etc. and further revel the mechanism between water and sediment transport during the flash flood This kind of relic-based study will generate bigger errors in regions with great bed deformation. In this study, we come up with numerical simulations to investigate the flash flood that happened in the Zhongdu river. The simulations are based on two-dimensional shallow water models coupled with sediment transport and bed deformation models. Based on the real water level and discharge profile measured by a hydrometric station nearby, the numerical simulation reproduced the flash flood in the valley. The results show the flood coverage, water level variation, and velocity distribution during the flood. The simulation offers great help in studying the damage-causing process. Furthermore, simulations without considering sediment transport are also carried out to study the impact of bed erosion and sedimentation. The study proved that, without considering bed deformation, the flood may be greatly underestimated, and the sediment lying in the valley has great impact on flood power.

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Impact of dissipation and dispersion terms on simulations of open-channel confluence flow using two-dimensional depth-averaged model

Cited by 10 publications

References 34 publications

Numerical assessments of bed morphological evolution in mountain river confluences under effects of hydro‐morphological factors

Numerical assessments of bed morphological evolution in mountain river confluences under effects of hydro‐morphological factors

Vertically layered flow structure at confluence of a reservoir and tributary carrying high sediment loads

Numerical Investigation of a Flash Flood Process that Occurred in Zhongdu River, Sichuan, China

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