Download or read book Using Machine Learning Particle Tracking and Grain Shape Modeling to Characterize Bedload Sediment Transport written by Matthew R. Rushlow (S.B.) and published by . This book was released on 2020 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rivers are generally understood through their bulk characteristics and on a river by river scale, while the motion and characteristics of the individual sediment that progresses through those rivers is poorly understood. This project sought to track the bed-load transport of individual natural and artificial sediment grains through a flume to understand the effects of grain shape on motion, and creation of multi spherical approximations of natural sediment grains for use in numerical simulations. Machine learning tools processed the position of millions of grains through a flume. Successful identification and tracking of nearly 75% of all grains within a flume, and multi spherical approximations of natural grains using 20 spheres or less that reproduced important shape characteristics of natural grains were achieved. Accurate grain locations allowed the possibility for velocities, accelerations, entrainments, and flux to be studied with uniquely high resolution. Efficient flume simulations that better represent actual sediment became possible.

Download or read book Stochastic Particle Tracking Modeling for Sediment Transport in Open Channel Flows written by Jungsun Oh and published by . This book was released on 2011 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sediment transport in flow has a practical impact on environmental and economic aspects of human society, for instance, water quality, hydraulic structures and land resources. A systematic understanding of the sediment transport processes is of critical significance to establish proper water resources and sediment management plans. Both random properties of flows and varying properties of sediment particles can induce stochastic nature of sediment particle movement in the flows. Thus, stochastic approaches or analyses are beneficial to analyzing the variability associated with the movement of sediment particles. In this context, the focus of this study is to model various features of sediment transport in open channel flow with stochastic approaches.^The scope of the study includes the following main issues: the movement of sediment particles in turbulent open channel flows in the occurrences of extreme flows, the deposition and resuspension processes of sediment particles, sediment concentrations and its uncertainty, and various modeling framework of stochastic particle tracking models. Turbulence in a flow is a primary source of stochastic property of particle movement in the flow. Furthermore, extreme flows that might occur occasionally in a random manner reinforce the randomness of the movement of sediment particles in the flow. The volatile flow velocity of extreme flows will not only affect the mean trend of particle movement but also intensify the uncertainty of particle movement. Specifically, since extreme flow events randomly occur per se, the random manner of the occurrences generates the stochastic property that affects the movement of sediment particles.^Thus, it is effective to employ stochastic approaches for describing sediment transport processes associated with uncertainty. Herein, both a & lsquo;stochastic diffusion process & rsquo; and a & lsquo;stochastic jump diffusion process & rsquo; are introduced to describe stochastic particle movement in open channel flows. The & lsquo;stochastic jump diffusion process & rsquo; represents the particle movement in response to extreme flow events that randomly occur in a turbulent open channel flow, whereas the & lsquo;stochastic diffusion process & rsquo; characterizes the particle movement in a turbulent open channel flow. As a result, both the stochastic diffusion particle tracking model (SD-PTM) and the stochastic jump diffusion particle tracking model (SJD-PTM) can present particle trajectories, and roughly estimated instantaneous velocities.^The ensemble statistics of the particle trajectories and velocities radically contain information on the stochastic characteristics of sediment particle movement. The SD-PTM and SJD-PTM to estimate particle trajectory and velocity is verified with data of Sumer and Oguz (1978), Muste and Patel (1997), Cuthberson and Ervine (2007) and Muste et al. (2009). The sediment concentration and sediment flux are highly-sought, practical variables in that the existence and amount of suspended sediments in surface waters have a direct influence on water quality and its suitability for drinking and industrial purposes. Especially, the estimation of sediment concentrations demonstrates the transporting process of suspended sediment through its spatial and temporal distributions. The sediment concentrations play a significant role as a pragmatic indicator in the decision making process.^Thus, the previous-stated particle-based stochastic approach for sediment transport is enhanced to predict the suspended sediment concentration, and to quantify the uncertainty of the sediment concentrations. The method also allows for particle entrainment into flows and particle settlement on the bed as main processes in open channel flows. Through multiple realizations of the particle movement with stochastic properties, the SD-PTM shows not only sediment concentrations at a specific location and time but also uncertainty for the estimated sediment concentrations. The proposed method, in this context, is a more straightforward method to evaluate uncertainty due to stochastic properties in the particle movement and a unique way to present the uncertainty of sediment concentrations. The proposed stochastic particle tracking model for sediment concentrations is verified with data of Coleman (1986).^The final goal of this study is to pursue further investigation into two different types of stochastic particle tracking approaches describing sediment particle movement associated with randomness. The different types of approaches are classified into the & lsquo;univariate & rsquo; and the & lsquo;multivariate & rsquo; stochastic particle tracking models according to the selection of key stochastic variables that describe the randomness of natural phenomena. In the & lsquo;univariate & rsquo; stochastic particle tracking model, one state vector (e.g., particle position) is regarded as a targeted variable. The above proposed models can be thought of as the & lsquo;univariate & rsquo; stochastic particle tracking model. In the & lsquo;multivariate & rsquo; stochastic particle tracking model, the sediment particle velocity and position are joint Markovian state variables, since the flow velocity evolves in time according to a generalized stochastic differential equation.^Model comparisons are performed and both models are verified with data of Sumer and Oguz (1978).

Download or read book A Particle Tracking Model for Sediment Transport in the Nearshore Zone written by D. M. L. Johnson and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Particle tracking model of sediment transport written by A. Kelsey and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stochastic Particle Tracking Modeling for Sediment Transport in Extreme Flow Environments written by 林彥廷 and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Particle Tracking Model of Sediment Transport written by A. Kelsey and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sampling Surface and Subsurface Particle size Distributions in Wadable Gravel and Cobble bed Streams for Analyses in Sediment Transport Hydraulics and Streambed Monitoring written by Kristin Bunte and published by . This book was released on 2001 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: This document provides guidance for sampling surface and subsurface sediment from wadable gravel-and cobble-bed streams. After a short introduction to streams types and classifications in gravel-bed rivers, the document explains the field and laboratory measurement of particle sizes and the statistical analysis of particle-size distributions. Analysis of particle parameters, including shape, density, and bulk density are also discussed. The document describes the spatial variability of bed-material particle sizes as well as the horizontal and vertical structure of particle deposits. The discussion of sampling procedures and equipment helps the user to make appropriate selections that support the sampling objective. Sample-size estimates may be obtained from empirical data or computed from statistical relationships between sample size and accuracy. The document explains a variety of methods, their usage and prerequisites. A detailed discussion of sampling schemes guides the user to select appropriate spatial sampling patterns necessary to produce representative samples.

Download or read book Discrete and Continuum Modelling of Grain Size Segregation written by Rémi Chassagne and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding particle size segregation is one of the great challenge in fluvial geomorphology. It is still notoriously difficult to predict sediment transport more accurately than within one order of magnitude. One of the main origin of this difficulty is particle size segregation, a granular process of particle sorting in the sediment bed. Size segregation is therefore a grain scale process impacting the morphological scale.This PhD presents a numerical study of size segregation as a granular process during bedload transport. A coupled fluid discrete element method (DEM) is used to study the infiltration of small particles in a large particle bed. This configuration, close to granular flows on erodible beds, is characterized by a particle velocity profile, a shear rate profile and an inertial number profile exponentially decreasing into the bed. It presents a particular segregation phenomenology with small particles infiltrating the bed as a travelling wave, the velocity being controlled by the inertial number at the bottom of the layer. The segregation velocity is observed dependent on the local small particle concentrations and on the size ratio. The segregation problem is also analyzed with an advection diffusion model. With advection and diffusion coefficients both proportional to the inertial number, the continuum model perfectly reproduces the dynamics observed in the DEM results.Very recently, a new segregation advection diffusion model has been derived based on particle scale forces, in particular a granular buoyancy force (or segregation force) and an inter-particle drag force. This provides new physically based parametrisations for the advection and diffusion coefficients. This new model is analysed in the bedload configuration, and reproduces qualitatively the DEM results. To improve the model, new dependencies on the inertial number and small particle concentration are proposed for the segregation and drag forces.Finally, the impact of size segregation on sediment transport is studied through the mobility of bidisperse already segregated particle beds. Large particles are placed above small ones, and it is observed that, in the same fluid and surface bed conditions, the transport rate is higher in the bidisperse configuration than in the monodisperse one. For the range of studied size ratio (r

Download or read book Discrete Particle Model for Bedload Sediment Transport in the Surf Zone written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Predicting the evolution of nearshore bathymetry from the highest uprush of the swash offshore to the location of wave breaking is a difficult problem of significant importance, with economic, legal, engineering, scientific, and military implications for coastal environments. Despite the apparent accessibility of the phenomena of interest, namely, the motion of sand under the forcing of waves and currents, the predictive capability of existing models for nearshore evolution is poor. A detailed study of the forces exerted on individual sand grains is undertaken in an effort to elucidate sediment transport mechanisms in the surf zone. New results indicate that fluid acceleration is a particularly important feature of surf zone transport; likewise, the processes of particle size segregation and the role of particle shape are newly explored. The study methodology employs computer simulations that describe the collective and individual motions of discrete particles immersed in a Newtonian fluid having essentially arbitrary density and viscosity. In this study all particle properties are those of quartz sand, and the fluid properties correspond to saltwater at 20 & deg;C. Such discrete-particle models, having a basis in molecular dynamics studies, have a broad range of applications in addition to the sedimentological one of interest here; for example, similar methodologies have been applied to traffic flow, schooling fish, crowd control, and other problems in which the particulate nature of the phenomenon is of critical importance.

Download or read book Particle Tracking Sediment Transport Model for the Buffalo River written by Pradeep Nagaraja and published by . This book was released on 2008 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: Particle tracking model (PTM) is developed to simulate sediment movement in a river. It includes the same processes as traditional Eulerian (control volume) based models, but adds the capability to follow the pathways of individual particles, which is useful for making remediation decisions that might include, for example, environmental dredging. The PTM tracks the movement of particles based on velocities and dispersion fields generated from a hydrodynamic model, which is a curvilinear, orthogonal grid-based model that can be conveniently used to follow the system boundaries. The movement of a particle is computed using a random walk algorithm. The PTM can function either as a stand-alone model or can be coupled to a hydrodynamic based model such as the Estuarine, Coastal and Ocean Model (ECOM), as was done in this study. The advantage of using the PTM as a stand-alone model is that it could be used independently for specific cases and hence, would save on computation time. However, it can be coupled with a hydrodynamic model in cases where the velocity and dispersion fields are sensitive to particle movements or bed elevation changes. The PTM includes boundary interactions such as reflection, deposition and resuspension, and can be compared with more traditional sediment transport models by correlating the number of particles in a grid cell to a concentration. The PTM has been used in an application to track the sediments in the Buffalo River, and provides a useful tool for current discussions of possible sediment remediation options.

Download or read book The Effects of Grain Size Heterogeneity on Sediment Transport Modeling written by Ross Steven Wickham and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Application of Queueing Theory and Stochastic Particle Tracking Model to Simulating Stochastic Sediment Transport written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigations of Grain Size Dependent Sediment Transport Phenomena on Multiple Scales written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Sediment transport in coastal and fluvial environments resulting from short time-scale processes of disturbance such as urbanization, mining, agriculture and military operations have significant impact on channel network and shoreline morphology, downstream water quality and ecosystems, and the integrity of land use applications. The scale and spatial distribution of these effects are largely attributable to the size distribution of the sediment grains that become eligible for transport due to disturbance. An improved understanding of advective and diffusive grain size dependent sediment transport phenomena will lead to the development of more accurate predictive models and preventative measures. To this end, three studies were performed that investigate grain-size dependent sediment transport on three different scales. Discrete particle computer simulations of sheet flow bedload transport on the scale of 0.1-100 millimeters were performed on a heterogeneous population of grains of various grain sizes. The relative transport rates and diffusivities of grains under both oscillatory and uniform, steady flow conditions were quantified. These findings suggest that, due to preferential vertical sorting of the largest grains to the top of the bed, a representative grain size that is functionally dependent on the applied flow parameters should be employed when parameterizing bed roughness. On the scale of 1-10m, experiments were performed to quantify the hydrodynamics and sediment capture efficiency of various baffles installed in a sediment retention pond, a commonly used sedimentation control measure in watershed applications. Analysis indicates that optimum sediment capture effectiveness may be achieved based on baffle permeability, pond geometry, and/or flow rate. Finally, on the scale of 10-1,000m, simulations were performed using a path sampling bivariate watershed erosion / deposition model in which grain size dependent terrain modification and pattern formation wer.

Download or read book Gravel Bed Rivers written by Daizo Tsutsumi and published by John Wiley & Sons. This book was released on 2017-07-05 with total page 850 pages. Available in PDF, EPUB and Kindle. Book excerpt: With contributions from key researchers across the globe, and edited by internationally recognized leading academics, Gravel-bed Rivers: Processes and Disasters presents the definitive review of current knowledge of gravel-bed rivers. Continuing an established and successful series of scholarly reports, this book consists of the papers presented at the 8th International Gravel-bed Rivers Workshop. Focusing on all the recent progress that has been made in the field, subjects covered include flow, physical modeling, sediment transport theory, techniques and instrumentation, morphodynamics and ecological topics, with special attention given to aspects of disasters relevant to sediment supply and integrated river management. This up-to-date compendium is essential reading for geomorphologists, river engineers and ecologists, river managers, fluvial sedimentologists and advanced students in these fields.

Download or read book The Bed load Function for Sediment Transportation in Open Channel Flows written by Hans Albert Einstein and published by . This book was released on 1950 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: