Turbulence-resolving Numerical Investigations of Coastal Bottom Boundary Layer and Fine Sediment Transport PDF Download

Author: Liangyi Yue
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
The bottom boundary layer in coastal ocean is of intrinsic scientific importance in many disciplines, serving as the near-bed passage where many benthic transport processes occur and it is a vital bridge connecting the wave propagation, currents and upper ocean processes with the seafloor. The present work focuses on the fluid dynamics in coastal bottom boundary layer (CBBL) and the associated sediment transport process using the technique of turbulence-resolving numerical simulation (TRNS). Particularly, we are interested in the entrainment, suspension and transport of fine sediment in the wave bottom boundary layer (WBBL) driven by surface gravity waves.

Author: Peter Nielsen
Publisher: World Scientific
ISBN: 9789810204730
Category : Science
Languages : en
Pages : 356

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Book Description
This book is intended as a useful handbook for professionals and researchers in the areas of Physical Oceanography, Marine Geology, Coastal Geomorphology and Coastal Engineering and as a text for graduate students in these fields. With its emphasis on boundary layer flow and basic sediment transport modelling, it is meant to help fill the gap between general hydrodynamic texts and descriptive texts on marine and coastal sedimentary processes. The book commences with a review of coastal bottom boundary layer flows including the boundary layer interaction between waves and steady currents. The concept of eddy viscosity for these flows is discussed in depth because of its relation to sediment diffusivity. The quasi-steady processes of sediment transport over flat beds are discussed. Small scale coastal bedforms and the corresponding hydraulic roughness are described. The motion of suspended sand particles is studied in detail with emphasis on the possible suspension maintaining mechanisms in coastal flows. Sediment pickup functions are provided for unsteady flows. A new combined convection-diffusion model is provided for suspended sediment distributions. Different methods of sediment transport model building are presented together with some classical models.

Author: Zhen Cheng
Publisher:
ISBN: 9781369351279
Category :
Languages : en
Pages : 230

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Book Description
Studying coastal processes is essential for the sustainability of human habitat and vibrancy of coastal economy. Coastal morphological evolution is caused by a wide range of coupled cross-shore and alongshore sediment transport processes associated with short waves, infra-gravity waves, and wave-induced currents. One of the key challenges was that the major transport occurs within bottom boundary layers and it is dictated by turbulence-sediment interactions and inter-granular interactions. Therefore, this study focuses on numerical investigations of sediment transport in the bottom wave boundary layers on continental shelves and nearshore zones, with emphasis on both fine sediment (mud) and sand transports. On the continental shelves, the sea floor is often covered with fine sediments (with settling velocity no more than a few mm/s). Wave-induced resuspension has been identified as one of the major mechanisms in the offshore delivery for fine sediments. A series of turbulence-resolving simulations were carried out to study the role of sediment resuspension/deposition on the bottom sediment transport. Specifically, we focus on how the critical shear stress of erosion and the settling velocity can determine the transport modes. At a given wave intensity associated with more energetic muddy shelves, three transport modes, namely the well-mixed transport (mode I), two-layer like transport with the formation of lutocline (mode II) and laminarized transport (mode III), are obtained by varying the critical shear stress of erosion or the settling velocity. A 2D parametric map is proposed to characterize the transition between transport modes as a function of the critical shear stress and the settling velocity at a fixed wave intensity. In addition, the uncertainties due to hindered settling and particle inertia effects on the transport modes were further studied. Simulation results confirmed that the effect of particle inertia is negligible for fine sediment in typical wave condition on continental shelves. On the other hand, the hindered settling with low gelling concentration can play a key role in sustaining a large amount of suspended sediments and results in the laminarized transport (mode III). Low gelling concentrations can also trigger the occurrence of gelling ignition, a state in which the erosion rate always exceeds the deposition rate. A sufficient condition for the occurrence of gelling ignition is hypothesized for a range of wave intensities as a function of sediment/floc properties and erodibility parameters. In the more energetic nearshore zones, the sea floor is often covered with sand (with settling velocity exceeds 1 cm/s). Based on the open-source CFD toolbox OpenFOAM, a multi-dimensional Eulerian two-phase modeling framework is developed for sediment transport applications. With closures of particle stresses and fluid-particle interactions, the model is able to resolve full sediment transport profiles without conventional bedload/suspended load assumptions. The turbulence-averaged model is based on a modified k-epsilon closure for the carrier flow turbulence and it was used to study momentary bed failure under sheet flow conditions. Model results revealed that the momentary bed failure and the resulting large transport rate were associated with a large erosion depth, which was triggered by the combination of large bed shear stresses and large horizontal pressure gradients. In order to better resolve turbulence-sediment interactions, the modeling framework was also extended with a 3D turbulence-resolving capability, where most of the turbulence-sediment interactions are directly resolved. The model is validated against a steady sheet flow experiment for coarse light particles. It is found that the drag-induced turbulence damping effect was more significant than the well-known density stratification for the flow condition and grain properties considered. Meanwhile, the turbulence-resolving model is able to reproduce bed intermittency, which was driven by turbulent ejection and sweep motions, similar to the laboratory observation. Finally, simulations for fine sand transport in oscillatory sheet flow demonstrate that the turbulence-resolving model is able to capture the enhanced transport layer thickness for fine sand, which may be related to the burst events near flow reversal. Several future research directions, including further improvements of the present modeling framework and science issues that may be significantly benefited from the present turbulence-resolving sediment transport framework, are recommended.

Author: B Mutlu Sumer
Publisher: World Scientific
ISBN: 9813234326
Category : Technology & Engineering
Languages : en
Pages : 758

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Book Description
This book discusses the subject of turbulence encountered in coastal and civil engineering.The primary aim of the book is to describe turbulence processes including transition to turbulence; mean and fluctuating flows in channels/pipes, and in currents; wave boundary layers (including boundary layers under solitary waves); streaming processes in wave boundary layers; turbulence processes in breaking waves including breaking solitary waves; turbulence processes such as bursting process and their implications for sediment transport; flow resistance in steady and wave boundary layers; and turbulent diffusion and dispersion processes in the coastal and river environment, including sediment transport due to diffusion/dispersion.Both phenomenological and statistical theories are described in great detail. Turbulence modelling is also described, and several examples for modelling of turbulence in steady flow and wave boundary layers are presented.The book ends with a chapter containing hands-on exercises on a wide variety of turbulent flows including experimental study of turbulence in an open-channel flow, using Laser Doppler Anemometry; Statistical, correlation and spectral analysis of turbulent air jet flow; Turbulence modelling of wave boundary layer flows; and numerical modelling of dispersion in a turbulent boundary layer, a set of exercises used by the authors in their Masters classes over many years.Although the book is essentially intended for professionals and researchers in the area of Coastal and Civil Engineering, and as a text book for graduate/post graduate students, the contents of the book will, however, additionally provide sufficient background in the study of turbulent flows relevant to many other disciplines, such as Wind Engineering, Mechanical Engineering, and Environmental Engineering.

Author: Liqin Zuo
Publisher: CRC Press
ISBN: 0429794029
Category : Science
Languages : en
Pages : 193

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Book Description
The evolution and utilization of estuarine and coastal regions are greatly restricted by sediment problems. This thesis aims to better understand fine sediment transport under combined action of waves and currents, especially in the wave-current bottom boundary layer (BBL). Field observations, experimental data analysis, theoretical analysis and numerical models are employed. Silt-dominated sediments are sensitive to flow dynamics and the suspended sediment concentration (SSC) increase rapidly under strong flow dynamics. This research unveils several fundamental aspects of silty sediment, i.e., the criterion of the incipient motion, the SSC profiles and their phase-averaged parameterization in wave-dominated conditions. An expression for sediment incipient motion is proposed for silt-sand sediment under combined wave and current conditions. A process based intra-wave 1DV model for flow-sediment dynamics near the bed is developed in combined wave-current conditions. The high concentration layer (HCL) was simulated and sensitivity analysis was carried out by the 1DV model on factors that impact the SSC in the HCL. Finally, based on the 1DV model, the formulations of the mean SSC profile of silt-sand sediments in wave conditions were proposed. The developed approaches are expected to be applied in engineering practice and further simulation.

Author: Yeulwoo Kim
Publisher:
ISBN: 9780438931909
Category :
Languages : en
Pages : 249

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Book Description
Understanding sediment transport driven by surface waves is key to a resilient coastal community and its sustainable development. To understand nearshore wave, turbulence and wave-driven sediment transport processes, this study focuses on utilizing a turbulence-resolving simulation approach and a multiphase flow methodology.

Author:
Publisher: World Scientific
ISBN:
Category :
Languages : en
Pages : 917

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Book Description

Author: B. Mutlu Sumer
Publisher: World Scientific Publishing Company
ISBN: 9789813234307
Category : Science
Languages : en
Pages : 0

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Book Description
This book discusses the subject of turbulence encountered in coastal and civil engineering. The primary aim of the book is to describe turbulence processes including transition to turbulence; mean and fluctuating flows in channels/pipes, and in currents; wave boundary layers (including boundary layers under solitary waves); streaming processes in wave boundary layers; turbulence processes in breaking waves including solitary breaking waves; turbulence processes such as bursting process and their implications for sediment transport; flow resistance in steady and wave boundary layers; and turbulent diffusion and dispersion processes in the coastal and river environment, including sediment transport due to diffusion/dispersion. Both phenomenological and statistical theories are described in great detail. Turbulence modelling is also described, and several examples for modelling of turbulence in steady flow and wave boundary layers are presented. The book ends with a chapter containing hands-on exercises on a wide variety of turbulent flows including experimental study of turbulence in an open-channel flow, using Laser Doppler Anemometry; Statistical, correlation and spectral analysis of turbulent air jet flow; Turbulence modelling of wave boundary layer flows; and numerical modelling of dispersion in a turbulent boundary layer, a set of exercises used by the authors in their Masters classes over many years. Although the book is essentially intended for professionals and researchers in the area of Coastal and Civil Engineering, and as a text book for graduate/post graduate students, the contents of the book will, however, additionally provide sufficient background in the study of turbulent flows relevant to many other disciplines, such as Wind Engineering, Mechanical Engineering, and Environmental Engineering.

Author: Ping Wang
Publisher: World Scientific
ISBN: 9814355534
Category : Science
Languages : en
Pages : 2751

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Book Description
This proceedings contains nearly 200 papers on cutting-edge research presented at the seventh international Symposium on Coastal Engineering and Science of Coastal Sediment Processes, held May 2OCo6, 2011, in Miami, Florida, USA. This technical specialty conference was devoted to promoting an interdisciplinary exchange of state-of-the-art knowledge among researchers in the fields of coastal engineering, geology, oceanography, and related disciplines, with a theme of bringing together theory and practice. Focusing on the physical aspects of sediment processes in various coastal environments, this three-volume conference proceedings provides findings from the latest research and newest engineering applications. Session topics cover a wide range including barrier-island morphodynamics and evolution, beach nourishment and shore protection, coastal dunes, cohesive sediment transport, field and laboratory measurements of sediment transport processes and numerical modeling, gravel transport, large-scale and long-term coastal changes, LiDAR and remote sensing, longshore and cross-shore sediment transport, marsh and wetlands, regional sediment management, river deltas, sea-level changes, shelf and sand bodies, shoreline changes, tidal inlets and navigation channels. A special session on recent research findings at the Northern Gulf of Mexico is also included."

Author: N. J. Clifford
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 386

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Book Description
Turbulence: Perspectives on Flow and Sediment Transport outlines the fundamental principles of the measurement and analysis of turbulent flow and sediment transport. It reviews laboratory work over the last three decades on near-boundary flow structure, as well as providing more recent research dealing with the high frequency monitoring and modelling of sediment transport. The research sections address aspects of turbulence characteristics and sediment behaviour in fluvial, tidal and aeolian boundary layers. Throughout, emphasis is upon the practicalities of measurement and modelling under field conditions. The effects of roughness transitions are extensively discussed and some of the most popular instrumentation is reviewed. This book brings together contributions from twenty researchers worldwide from many disciplines connected with earth sciences, engineering and fluid dynamics, providing both review material and some of the latest research into the small-scale interactions of turbulence and sediment transport in geophysical boundary layers. The book is ideally suited to a wide audience, from advanced undergraduate level onwards.