Download or read book Modeling Sediment Transport in the Sheet Flow Layer Using a Mixture Approach written by Tyler J. Hesser and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Due to the existence of sheet flow during storm events, numerically quantifying sediment transport during sheet flow conditions is an important step in understanding coastal dynamics. Traditional methods for modeling sediment transport require solving separate equations for fluid and particle motion. We have chosen an alternate approach that assumes a system containing sediment particles can be approximated as a mixture having variable density and viscosity that depend on the local sediment concentration. Here, the interactions are expressed through the mixture viscosity and a stress-induced diffusion term. There are five governing equations that describe the flow field the mixture continuity and momentum equations, and a species continuity equation for the sediment. The addition of a bed-stiffness coefficient to simulate particle pressures in the bed has increased the consistency of the model results. This model which was developed for Crosstex has shown promising comparisons to Horikawa laboratory data demonstrating the effectiveness of the mixture model in simulating sediment transport in the sheet flow layer.
Download or read book Modelling Sheet Flow Sediment Transport in Wave Bottom Boundary Layers Using Discrete Element Modelling written by and published by . This book was released on 2004 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sediment transport in oscillatory boundary layers is a driving mechanism of coastal geomorphologic change. Most formulae for bed-load transport in near-shore regions subsume the smallest-scale physics of the phenomena by parameterizing interactions between particles. In contrast, the authors directly simulate granular physics in the wave-bottom boundary layer using a discrete-element model consisting of a three-dimensional particle phase coupled to a one-dimensional fluid phase via Newton's Third Law through forces of buoyancy, drag, and added mass. The particulate sediment phase is modeled using discrete, non-spherical particles formed to approximate natural grains by overlapping two spheres. Both the size of each sphere and the degree of overlap can be varied for these composite particles to generate a range of non-spherical grains. Simulations of particles having a range of shapes showed that the critical angle - the angle at which a grain pile will fail when tilted slowly from rest - increases from approximately 26 degrees for spherical particles to nearly 39 degrees for highly non-spherical composite particles having a dumbbell shape. Simulations of oscillatory sheet flow were conducted using composite particles with an angle of repose of approximately 33 degrees and a Corey shape factor greater than about 0.8, similar to the properties of beach sand. The results from the sheet-flow simulations with composite particles agreed more closely with laboratory measurements than similar simulations conducted using spherical particles. The findings suggest that particle shape may be an important factor for determining bed-load flux, particularly for larger bed slopes. (5 figures, 18 refs.).
Download or read book An Approach to the Sediment Transport Problem from General Physics written by Ralph Alger Bagnold and published by . This book was released on 1966 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: From considerations of energy balance and of mechanical equilibrium, a mathematical expression is derived relating the rates of sediment transport as bedload and as suspended load to the expenditure of power by a statistically steady flow of water.
Download or read book A Multi dimensional Two phase Flow Modeling Framework for Sediment Transport Applications written by Zhen Cheng and published by . This book was released on 2016 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Numerical Modeling of Sediment Transport Near the Bed Using a Two phase Flow Approach written by Andrea Emilia Gonzalez and published by . This book was released on 2008 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modeling Sediment Transport Using a Two phase Flow Approach written by Leslie J.C. Aquino and published by . This book was released on 2001 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Sediment Transport written by Albert Gyr and published by Springer Science & Business Media. This book was released on 2006-09-21 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook discusses the fundamental principles of sediment transport in the geophysical context of rivers. It is intended as both a course textbook and as a guide for the practical engineer. It begins begin by describing phenomena such as bed load and suspension transport from a classical perspective. Concepts from turbulent flow regime are introduced to address the limitations of the classical approach to various aspects of sediment transport.
Download or read book Two phase Modeling of Granular Sediment for Sheet Flows and Scour written by Laurent Olivier Amoudry and published by . This book was released on 2008 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transport of Sediment Mixtures with Large Ranges of Grain Sizes written by Hans Albert Einstein and published by . This book was released on 1953 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modelling and Analysis of Fine Sediment Transport in Wave Current Bottom Boundary Layer written by Liqin Zuo and published by CRC Press. This book was released on 2018-06-19 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book A Two phase Flow Approach for Sediment Transport written by Tian-Jian Hsu and published by . This book was released on 2002 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Sediment Transport written by Silvia Susana Ginsberg and published by BoD – Books on Demand. This book was released on 2011-04-26 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sediment transport is a book that covers a wide variety of subject matters. It combines the personal and professional experience of the authors on solid particles transport and related problems, whose expertise is focused in aqueous systems and in laboratory flumes. This includes a series of chapters on hydrodynamics and their relationship with sediment transport and morphological development. The different contributions deal with issues such as the sediment transport modeling; sediment dynamics in stream confluence or river diversion, in meandering channels, at interconnected tidal channels system; changes in sediment transport under fine materials, cohesive materials and ice cover; environmental remediation of contaminated fine sediments. This is an invaluable interdisciplinary textbook and an important contribution to the sediment transport field. I strongly recommend this textbook to those in charge of conducting research on engineering issues or wishing to deal with equally important scientific problems.
Download or read book Theoretical and Numerical Modeling of Suspended Sediment Transport in Open Channels Using an Eulerian Eulerian Two phase Flow Approach written by Sanjeev Kumar Jha and published by . This book was released on 2009 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanics of Sediment Transport written by A. Mueller and published by CRC Press. This book was released on 2020-08-26 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the studies on sediment transport in suspension and sediment transport in steep channels. It discusses the degradation and particle sorting processes.
Download or read book Sediment Transport Technology written by Daryl B. Simons and published by Water Resources Publication. This book was released on 1992 with total page 928 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Twelve Selected Computer Stream Sedimentation Models Developed in the United States written by Shou-shan Fan and published by . This book was released on 1988 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Sediment Transport in Oscillatory Boundary Layers Under Sheet flow Conditions written by Abdullah Abdul-Aziz Al-Salem and published by . This book was released on 1993 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt:
