Fully Coupled Robust Shallow Water Flow and Sediment Transport Model on Unstructured Grids PDF Download

Author: Jiaheng Zhao
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Xin Liu
Publisher:
ISBN:
Category :
Languages : en
Pages :

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This Ph.D. thesis aims to develop numerical models for two-dimensional and three-dimensional shallow water systems over mobile beds. In order to accomplish the goal of this dissertation, the following sub-projects are defined and completed. 1: The first sub-project consists in developing a robust two-dimensional coupled numerical model based on an unstructured mesh, which can simulate rapidly varying flows over an erodible bed involving wet-dry fronts that is a complex yet practically important problem. In this task, the central-upwind scheme is extended to simulation of bed erosion and sediment transport, a modified shallow water system is adopted to improve the model, a wetting and drying scheme is proposed for tracking wet-dry interfaces and stably predict the bed erosion near wet-dry area. The shallow water, sediment transport and bed evolution equations are coupled in the governing system. The proposed model can efficiently track wetting and drying interfaces while preserving stability in simulating the bed erosion near the wet-dry fronts. The additional terms in shallow water equations can improve the accuracy of the simulation when intense sediment-exchange exists; the central-upwind method adopted in the current study shows great accuracy and efficiency compared with other popular solvers; the developed model is robust, efficient and accurate in dealing with various challenging cases. 2: The second sub-project consists in developing a novel numerical scheme for a coupled two-dimensional hyperbolic system consisting of the shallow water equations with friction terms coupled with the equations modeling the sediment transport and bed evolution. The resulting 5*5 hyperbolic system of balance laws is numerically solved using a Godunov-type central-upwind scheme on a triangular grid. A spatially second-order and temporally third-order central-upwind scheme has been derived to discretize the conservative hyperbolic sub-system. However, such schemes need a correct evaluation of local wave speeds to avoid instabilities. To address such an issue, a mathematical result by the Lagrange theorem is used in the proposed scheme. Consequently, a computationally expensive process of finding all of the eigenvalues of the Jacobian matrices is avoided: The upper/lower bounds on the largest/smallest local speeds of propagation are estimated using the Lagrange theorem. In addition, a special discretization of the bed-slope term is proposed to guarantee the well-balanced property of the designed scheme. 3: The third sub-project consists in designing a novel scheme to estimate bed-load fluxes which can produce more accurate results than the previously reported coupled model. Using a pair of local wave speeds different from those used for the flow, a novel wave estimator in conjunction with the central upwind method is proposed and successfully applied to the coupled water-sediment system involving a rapid bed-erosion process. It was demonstrated that, in comparison with the decoupled model, applying the proposed novel scheme to approximate the bed-load fluxes can successfully avoid the numerical oscillations caused by simple and less stable schemes, e.g. simple upwind methods; in comparison with the coupled model using same flux-estimator for both hydrodynamic and morphological systems, the proposed numerical scheme successfully prevents excessive numerical diffusion for prediction of bed evolution. Consequently, the proposed scheme has advantages in terms of accuracy which are shown in several numerical tests. In addition, analytical expressions have been provided for calculating the eigenvalues of the coupled shallow-water-Exner system, which greatly enhances the efficiency of the proposed method. 4: The fourth sub-project consists in developing a three-dimensional numerical model for the simulation of unsteady non-hydrostatic shallow water flows on unstructured grids using the finite volume method. The free surface variations are modeled by a characteristics-based scheme which simulates sub- and super-critical flows. Three-dimensional velocity components are considered in a collocated arrangement with a sigma coordinate system. A special treatment of the pressure term is developed to avoid the water surface oscillations. Convective and diffusive terms are approximated explicitly, and an implicit discretization is used for the pressure term. The unstructured grid in the horizontal direction and the sigma coordinate in the vertical direction facilitate the use of the model in complicated geometries. 5: The fifth sub-project consists in developing a well-balanced three-dimensional shallow water model which is able to simulate shock waves over dry bed. Due to the hydrostatic simplification of the vertical momentum equation, the governing system of equations is not hyperbolic and can not be solved using standard hyperbolic solvers. That is, one can not use a high-order Godunov-type scheme to compute all fluxes through cell-interfaces. This may cause the model to fail in simulations of some unsteady-flows with discontinuities, e.g., dam-break flows and floods. To overcome this difficulty, a novel numerical scheme for the three-dimensional shallow water equations is proposed using a relaxation approach in order to convert the system to a hyperbolic one. Thus, a high-order Godunov-type central-upwind scheme based on the finite volume method can be applied to approximate the numerical fluxes. The proposed model can also preserve the ``lake at rest'' state and positivity of water depth over irregular bottom topographies based on special reconstruction of the corresponding parameters. 6: The sixth sub-project consists in extending the result of the fifth sub-project to development of a three-dimensional numerical model for shallow water flows over mobile beds, which is able to simulate morphological evolutions under shock waves, e.g. dam-break flows. The hydrodynamic model solves the three-dimensional shallow water equations using a finite volume method on prismatic cells in sigma coordinates based on the scheme prposed in sub-project 5. The morphodynamic model solves an Exner equation consisting of bed-load sediment transportation. The performance of the proposed model has been demonstrated by several laboratory experiments of dam-break flows over mobile beds.

Author: Jingming Hou
Publisher:
ISBN: 9783844018578
Category :
Languages : en
Pages : 86

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Author: Tetsuya Sumi
Publisher: Springer Nature
ISBN: 9811629048
Category : Nature
Languages : en
Pages : 559

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This open access book brings together research studies, developments, and application-related flash flood topics on wadi systems in arid regions. The major merit of this comprehensive book is its focus on research and technical papers as well as case study applications in different regions worldwide that cover many topics and answer several scientific questions. The book chapters comprehensively and significantly highlight different scientific research disciplines related to wadi flash floods, including climatology, hydrological models, new monitoring techniques, remote sensing techniques, field investigations, international collaboration projects, risk assessment and mitigation, sedimentation and sediment transport, and groundwater quality and quantity assessment and management. In this book, the contributing authors (engineers, researchers, and professionals) introduce their recent scientific findings to develop suitable, applicable, and innovative tools for forecasting, mitigation, and water management as well as society development under seven main research themes as follows: Part 1. Wadi Flash Flood Challenges and Strategies Part 2. Hydrometeorology and Climate Changes Part 3. Rainfall–Runoff Modeling and Approaches Part 4. Disaster Risk Reduction and Mitigation Part 5. Reservoir Sedimentation and Sediment Yield Part 6. Groundwater Management Part 7. Application and Case Studies The book includes selected high-quality papers from five series of the International Symposium on Flash Floods in Wadi Systems (ISFF) that were held in 2015, 2016, 2017, 2018, and 2020 in Japan, Egypt, Oman, Morocco, and Japan, respectively. These collections of chapters could provide valuable guidance and scientific content not only for academics, researchers, and students but also for decision-makers in the MENA region and worldwide.

Author: Vanesa Magar
Publisher: CRC Press
ISBN: 1498753485
Category : Science
Languages : en
Pages : 231

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This reference for engineers, and graduate students covers sediment transport and morphodynamics modelling in nearshore environments. It presents the fundamentals required for understanding the physics and for setting up numerical models. This book covers hydrodynamics of estuarine and coastal environments, properties of seafloor and estuarine composition, and hydroenvironmental interactions; emphasising the inter-relations of small- and large-scale processes, and short- and large-evolution timescales. The focus is, principally, on the application of shallow-water theory, but some surface wave models, and coupling of shallow-water models with surface waves is also discussed to some extent. The guidance on running regional models and the case studies presented are directed to managed realignment, coastal protection, climate change impacts, and offshore renewables. Key features: Gives a balanced review of this rich interdisciplinary area Bridges practical engineering and research Offers both large- and small-scale application Suits graduate students and researchers as well as consulting engineers Vanesa Magar is a senior researcher and associate professor at the Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE) in Baja California, Mexico. She was formerly a researcher and then a lecturer at Plymouth University, UK.

Author: E. F. Toro
Publisher:
ISBN:
Category : Mathematics
Languages : en
Pages : 336

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The first of its kind in the field, this title examines the use of modern, shock-capturing finite volume numerical methods, in the solution of partial differential equations associated with free-surface flows, which satisfy the shallow-water type assumption (including shallow water flows, dense gases and mixtures of materials as special samples). Starting with a general presentation of the governing equations for free-surface shallow flows and a discussion of their physical applicability, the book goes on to analyse the mathematical properties of the equations, in preparation for the presentation of the exact solution of the Riemann problem for wet and dry beds. After a general introduction to the finite volume approach, several chapters are then devoted to describing a variety of modern shock-capturing finite volume numerical methods, including Godunov methods of the upwind and centred type. Approximate Riemann solvers following various approaches are studied in detail as is their use in the Godunov approach for constructing low and high-order upwind TVD methods. Centred TVD schemes are also presented. Two chapters are then devoted to practical applications. The book finishes with an overview of potential practical applications of the methods studied, along with appropriate reference to sources of further information. Features include: * Algorithmic and practical presentation of the methods * Practical applications such as dam-break modelling and the study of bore reflection patterns in two space dimensions * Sample computer programs and accompanying numerical software (details available at www.numeritek.com) The book is suitable for teaching postgraduate students of civil, mechanical, hydraulic and environmental engineering, meteorology, oceanography, fluid mechanics and applied mathematics. Selected portions of the material may also be useful in teaching final year undergraduate students in the above disciplines. The contents will also be of interest to research scientists and engineers in academia and research and consultancy laboratories.

Author: Jean-Michel Hervouet
Publisher: John Wiley & Sons
ISBN: 9780470319635
Category : Computers
Languages : en
Pages : 360

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A definitive guide for accurate state-of-the-art modelling of free surface flows Understanding the dynamics of free surface flows is the starting point of many environmental studies, impact studies, and waterworks design. Typical applications, once the flows are known, are water quality, dam impact and safety, pollutant control, and sediment transport. These studies used to be done in the past with scale models, but these are now being replaced by numerical simulation performed by software suites called “hydro-informatic systems”. The Telemac system is the leading software package worldwide, and has been developed by Electricité de France and Jean-Michel Hervouet, who is the head and main developer of the Telemac project. Written by a leading authority on Computational Fluid Dynamics, the book aims to provide environmentalists, hydrologists, and engineers using hydro-informatic systems such as Telemac and the finite element method, with the knowledge of the basic principles, capabilities, different hypotheses, and limitations. In particular this book: presents the theory for understanding hydrodynamics through an extensive array of case studies such as tides, tsunamis, storm surges, floods, bores, dam break flood waves, density driven currents, hydraulic jumps, making this a principal reference on the topic gives a detailed examination and analysis of the notorious Malpasset dam failure includes a coherent description of finite elements in shallow water delivers a significant treatment of the state-of-the-art flow modelling techniques using Telemac, developed by Electricité de France provides the fundamental physics and theory of free surface flows to be utilised by courses on environmental flows Hydrodynamics of Free Surface Flows is essential reading for those involved in computational fluid dynamics and environmental impact assessments, as well as hydrologists, and bridge, coastal and dam engineers. Guiding readers from fundamental theory to the more advanced topics in the application of the finite element method and the Telemac System, this book is a key reference for a broad audience of students, lecturers, researchers and consultants, right through to the community of users of hydro-informatics systems.

Author: Siamak Komaei
Publisher:
ISBN: 9783486630725
Category :
Languages : en
Pages : 124

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Author: Abdul A. Khan
Publisher: CRC Press
ISBN: 1482226022
Category : Science
Languages : en
Pages : 208

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This book introduces the discontinuous Galerkin (DG) method and its application to shallow water flows. The emphasis is to show details and modifications required to apply the scheme to real-world flow problems. It allows the readers to understand and develop robust and efficient computer simulation models that can be used to model flow, contaminant transport, and other factors in rivers and coastal environments. The book includes a large set of tests to illustrate the use of the model for a wide range of applications.

Author: Weiming Wu
Publisher: CRC Press
ISBN: 0415449618
Category : Technology & Engineering
Languages : en
Pages : 494

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Book Description
Comprehensive text on the fundamentals of modeling flow and sediment transport in rivers treating both physical principles and numerical methods for various degrees of complexity. Includes 1-D, 2-D (both depth- and width-averaged) and 3-D models, as well as the integration and coupling of these models. Contains a broad selection of numerical methods for open-channel flows, such as the SIMPLE(C) algorithms on staggered and non-staggered grids, the projection method, and the stream function and vorticity method. The state-of-the-art in sediment transport modeling approaches is described, such as non-equilibrium transport models, non-uniform total-load transport models, and semi-coupled and coupled procedures for flow and sediment calculations. Sediment transport theory is discussed and many newly-developed, non-uniform sediment transport formulae are presented. The many worked examples illustrate various conditions, such as reservoir sedimentation; channel erosion due to dam construction; channel widening and meandering; local scour around in-stream hydraulic structures; vegetation effects on channel morphodynamic processes; cohesive sediment transport; dam-break fluvial processes and contaminant transport. Recommended as a reference guide for river and hydraulic engineers and as a course text for teaching sediment transport modeling, computational free-surface flow, and computational river dynamics to senior students.