Modelling of fast hydraulic transients: issues, challenges, perspectives

Zech, Yves; Frazao, Sandra Soares; Emelen, Sylvie Van

doi:10.1051/lhb/20150049

Cited by 5 publications

(3 citation statements)

References 18 publications

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“…Regardless of a model's complexity, all numerical models make approximations and thus present limitations that can easily lead to inaccurate predictions (Rowinśki & Radecki-Pawlik, 2015;Toombes & Chanson, 2011). The main problems presented in regard to hydraulic modelling of floods are (Liang & Borthwick, 2009;Néelz & Pender, 2010;Zech, et al, 2015): (1) the numerical instabilities present in high-resolution grids, (2) the computational time, (3) the modelling of the moving wet-dry interface, specifically the arrival time of the wave front in fluvial floods, (4) the maximum water depth and, finally (5) the representation of complex boundaries.…”

Section: Background 1521 Numerical Methods Used To Model Extreme Evmentioning

confidence: 99%

Boscastle case of flash flood modelling and hazards reduction

Stamataki¹

2021

Water-Wise Cities and Sustainable Water Systems: Concepts, Technologies, and Applications

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An increase in the frequency and magnitude of flooding is one expected consequence of climate change. The UN Office for Disaster Risk Reduction (UNISDR) and the Belgian-based Centre for Research on the Epidemiology of Disasters (CRED) in their 2015 report 'The Human Cost of Weather Related Disasters' associated 157 000 deaths with flooding since 1995. In the last 20 years, floods accounted for 47% of all other weather disasters with 3062 individual events resulting in 2.3 billion people being affected by floods, an alarming number (UNISDR, 2015). The event occurrence of different geophysical, meteorological, hydrological and climatological events from 1970 to 2017 were assembled by the International Disaster Database in CRED and are presented in Figure 15.1. A significant increase is seen in extreme events and especially the number of floods (EMDAT, 2017). In line with the above-mentioned predictions, a considerable increase is also expected in the intensity and frequency of extreme precipitation events. This chapter's focus will be on flash floods which are a destructive natural hazard with one of the highest mortalities. They are short duration floods associated with excessive amounts of rainfall and their different causes include a short duration

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Section: Background 1521 Numerical Methods Used To Model Extreme Evmentioning

confidence: 99%

Boscastle case of flash flood modelling and hazards reduction

Stamataki¹

2021

Water-Wise Cities and Sustainable Water Systems: Concepts, Technologies, and Applications

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“…Hu and Cao, ; Hu et al ., ) as well as sharply stratified processes (e.g. Li et al ., ; Cao et al ., ; Zech et al , ).…”

Section: Mathematical Modelmentioning

confidence: 97%

Numerical modelling of alternate bar formation, development and sediment sorting in straight channels

Qian

Cao

Liu

et al. 2016

Earth Surf Processes Landf

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A two-dimensional shallow water hydro-sediment-morphodynamic model is applied to investigate alternate bar formation, development and sediment sorting in straight channels. The model is coupled, explicitly incorporating the flowsediment-bed interactions by using the full mass and momentum conservation equations, which are numerically solved by a well-balanced version of the finite volume Slope Limiter Centred (SLIC) scheme. The model is first tested against a flume experiment on alternate bars formed over a uniform sediment bed, which clearly exhibits processes of bar formation, migrating and finally approaching an equilibrium state. Then it is applied to another flume experiment on alternate bars due to non-uniform sediment transport. The computational results are evaluated, with a focus on the longitudinal and vertical sediment sorting. It is argued for the first time that the inconsistent sediment sorting patterns observed in previous studies are determined by different sediment transport conditions, i.e. full versus partial transport. When a condition of full transport is achieved, under which all size fractions are fully mobilized and transported, the longitudinal surface sediment shows a sorting pattern of coarse-on-head and fine-in-pool, and the vertical substrate sediment exhibits an immobile-fine-coarse structure upwards. In contrast, for a partial transport condition, under which only finer fraction participates in the transport process, an opposite longitudinal pattern (i.e. fine-on-head and coarse-inpool) and a different vertical structure (i.e. immobile-coarse-fine) are observed. Concurrently, numerical experiments with specified conditions show that the critical aspect ratio for the formation of migrating alternate bars is approximately equal to 12. With the increase of the aspect ratio, the bar length grows gradually, while the bar height increases rapidly for moderate values of the aspect ratio and then keeps nearly stable. The bar celerity, however, is weakly sensitive to the variation of this ratio.

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“…A wide range of fluvial processes have been investigated, including dam-break floods over erodible beds (Cao et al, 2004;Capart & Young, 1998;Huang et al, 2012Huang et al, , 2014Wu & Wang, 2007;Xia et al, 2010) and morphodynamic processes (Nicholas et al, 2013;Qian et al, 2017;Wang et al, 2008;Wu, 2007;Xie, 1990). In fact, as pointed out by Cao et al (2017), the SHSM equations have been extended to model coastal processes (Kim, 2015;Xiao et al, 2010;Zhu & Dodd, 2015), watershed erosion processes (Kim et al, 2013), subaqueous sediment-laden flows and turbidity currents (Hu & Cao, 2009;Hu et al, 2012), and sharply stratified processes (Li et al, 2013;Spinewine & Capart, 2013;Zech et al, 2015). Most recently, shallow water twophase models have been developed to better resolve fluvial processes (Cristo et al, 2015;Li et al, 2017) and debris flows (Li et al, 2018a(Li et al, , 2018b).…”

Section: Introductionmentioning

confidence: 99%

Approximate Solutions for Ideal Dam‐Break Sediment‐Laden Flows on Uniform Slopes

Cao

Borthwick

et al. 2018

Water Resources Research

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Shallow water hydro‐sediment‐morphodynamic (SHSM) models have been applied increasingly widely in hydraulic engineering and geomorphological studies over the past few decades. Analytical and approximate solutions are usually sought to verify such models and therefore confirm their credibility. Dam‐break flows are often evoked because such flows normally feature shock waves and contact discontinuities that warrant refined numerical schemes to solve. While analytical and approximate solutions to clear‐water dam‐break flows have been available for some time, such solutions are rare for sediment transport in dam‐break flows. Here we aim to derive approximate solutions for ideal dam‐break sediment‐laden flows resulting from the sudden release of a finite volume of frictionless, incompressible water‐sediment mixture on a uniform slope. The approximate solutions are presented for three typical sediment transport scenarios, i.e., pure advection, pure sedimentation, and concurrent entrainment and deposition. Although the cases considered in this paper are not real, the approximate solutions derived facilitate suitable benchmark tests for evaluating SHSM models, especially presently when shock waves can be numerically resolved accurately with a suite of finite volume methods, while the accuracy of the numerical solutions of contact discontinuities in sediment transport remains generally poorer.

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Modelling of fast hydraulic transients: issues, challenges, perspectives

Cited by 5 publications

References 18 publications

Boscastle case of flash flood modelling and hazards reduction

Boscastle case of flash flood modelling and hazards reduction

Numerical modelling of alternate bar formation, development and sediment sorting in straight channels

Approximate Solutions for Ideal Dam‐Break Sediment‐Laden Flows on Uniform Slopes

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