Sediment Transport, Part III: Bed Forms and Alluvial Roughness
01 Dec 1984-Journal of Hydraulic Engineering (American Society of Civil Engineers)-Vol. 110, Iss: 12, pp 1733-1754
TL;DR: In this paper, a verification analysis using about 1,500 (alternative) reliable flume and field data shows good results in predicting the hydraulic roughness (friction factor).
Abstract: A method is presented that makes the classification of bed forms, the prediction of the bed‐form dimensions and the effective hydraulic roughness of the bed forms feasible. The proposed relationships are based on the analysis of reliable flume and field data. A verification analysis using about 1,500 (alternative) reliable flume and field data shows good results in predicting the hydraulic roughness (friction factor). For field conditions, the proposed method yields considerably better results than previously proposed methods, which are reviewed here. The proposed method has also been used to predict the flow depth and the total bed‐material load.
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TL;DR: In this paper, the effect of fine silt on the bed composition and on initiation of motion (critical conditions) of sediment beds over the full range of conditions (silts to gravel) is discussed.
Abstract: Attention is given to the properties of sediment beds over the full range of conditions (silts to gravel), in particular the effect of fine silt on the bed composition and on initiation of motion (critical conditions) is discussed. High-quality bed-load transport data sets are identified and analyzed, showing that the bed-load transport in the sand range is related to velocity to power 2.5. The bed-load transport is not much affected by particle size. The prediction of bed roughness is addressed and the prediction of bed-load transport in steady river flow is extended to coastal flow applying an intrawave approach. Simplified bed-load transport formulas are presented, which can be used to obtain a quick estimate of bed-load transport in river and coastal flows. It is shown that the sediment transport of fine silts to coarse sand can be described in a unified model framework using fairly simple expressions. The proposed model is fully predictive in the sense that only the basic hydrodynamic parameters (dep...
604 citations
Cites background from "Sediment Transport, Part III: Bed F..."
...van Rijn 1984c, 1993 has shown that megaripples and dunes are related to the flow depth h and to the flow regime mobility parameter....
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...The physical bed form roughness ks,c,mr of the megaripples and dunes ks,c,d is roughly on the order of half the bed form height van Rijn 1984c, 1993 ....
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... van Rijn 1984c, 1993 proposed a simplified formula for bedload transport in current only conditions, which reads as...
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TL;DR: In this paper, the authors discuss the differences between momentum and energy resistances, between point, cross-sectional and reach resistance coefficients, as well as compound/composite channel resistance.
Abstract: In 1965, Rouse critically reviewed hydraulic resistance in open channels on the basis of fluid mechanics. He pointed out the effects of cross-sectional shape, boundary nonuniformity, and flow unsteadiness, in addition to viscosity and wall roughness that are commonly considered. This paper extends that study by discussing the differences between momentum and energy resistances, between point, cross-sectional and reach resistance coefficients, as well as compound/composite channel resistance. Certain resistance phenomena can be explained with the inner and outer laws of boundary layer theory. The issue of linear-separation approach versus nonlinear approach to alluvial channel resistances also is discussed. This review indicates the need for extensive further research on the subject.
520 citations
30 Jun 1999
TL;DR: In this paper, the authors present a synthesis of information gleaned from more than 800 papers spanning the fields of hydraulic engineering, mathematics, physics, geology, rheology and chemistry, giving the reader a profound understanding of the present status and direction of the industry's research efforts.
Abstract: Nearly 40 years of theoretical development and practical experience has been incorporated in this book, which has won numerous awards as a scientific and technical publication in China. Now updated and fully translated into English, this volume is the first attempt in the field to unify the movement of sediment and boundary conditions. Going far beyond any book of its kind, it presents a synthetic analysis and thorough coverage of many schools of thought and provides practical survey of this discipline of the science. The authors introduce a synthesis of information gleaned from more than 800 papers spanning the fields of hydraulic engineering, mathematics, physics, geology, rheology, and chemistry, giving the reader a profound understanding of the present status and direction of the industry's research efforts. The volume includes chapters dedicated to rate phenomena and topics such as hyperconcentrated flows, effect of sediment existence on water flow, large-scale hydraulic construction on sediment-laden streams, and specialized research not available outside of China.
506 citations
TL;DR: In this paper, the problem of suspended sediment transport in river and coastal flows is addressed and a simplified transport formula is presented, which can be used to obtain a quick estimate of suspended transport.
Abstract: The problem of suspended sediment transport in river and coastal flows is addressed. High-quality field data of river and coastal flows have been selected and clustered into four particle size classes 60-100, 100-200, 200-400, and 400-600 m. The suspended sand transport is found to be strongly dependent on particle size and on current velocity. The suspended sand transport in the coastal zone is found to be strongly dependent on the relative wave height Hs/h, particularly for current velocities in the range 0.2-0.5 m/s. The time-averaged over the wave period advection-diffusion equation is applied to compute the time-averaged sand concentration profile for combined current and wave conditions. Flocculation, hindered settling, and stratification effects are included by fairly simple expressions. The bed-shear stress is based on a new bed roughness predictor. The reference concentration function has been recalibrated using laboratory and field data for combined steady and oscillatory flow. The computed transport rates show reasonably good agreement within a factor of 2 with measured values for velocities in the range of 0.6-1.8 m/s and sediments in the range of 60-600 m. The proposed method underpredicts in the low-velocity range 0.6 m/s. A new simplified transport formula is presented, which can be used to obtain a quick estimate of suspended transport. The modeling of wash load transport in river flow based on the energy concept of Bagnold shows that an extremely large amount of very fine sediment clay and very fine silt can be transported by the flow.
455 citations
TL;DR: A 3D numerical model for calculating flow and sediment transport in open channels is presented in this article, where the free-surface and roughness treatments are introduced for open-channel flow; in particular the water level is determined from a 2D Poisson equation derived from 2D depth-averaged momentum equations.
Abstract: A 3D numerical model for calculating flow and sediment transport in open channels is presented. The flow is calculated by solving the full Reynolds-averaged Navier-Stokes equations with the k − e turbulence model. Special free-surface and roughness treatments are introduced for open-channel flow; in particular the water level is determined from a 2D Poisson equation derived from 2D depth-averaged momentum equations. Suspended-load transport is simulated through the general convection-diffusion equation with an empirical settling-velocity term. This equation and the flow equations are solved numerically with a finite-volume method on an adaptive, nonstaggered grid. Bed-load transport is simulated with a nonequilibrium method and the bed deformation is obtained from an overall mass-balance equation. The suspended-load model is tested for channel flow situations with net entrainment from a loose bed and with net deposition, and the full 3D total-load model is validated by calculating the flow and sediment tr...
403 citations
References
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TL;DR: In this article, a method is presented which enables the computation of the bed-load transport as the product of the saltation height, the particle velocity and the bed load concentration.
Abstract: A method is presented which enables the computation of the bed-load transport as the product of the saltation height, the particle velocity and the bed-load concentration. The equations of motions for a solitary particle are solved numerically to determine the saltation height and particle velocity. Experiments with gravel particles (transported as bed load) are selected to calibrate the mathematical model using the lift coefficient as a free parameter. The model is used to compute the saltation heights and lengths for a range of flow conditions. The computational results are used to determine simple relationships for the saltation characteristics. Measured transport rates of the bed load are used to compute the sediment concentration in the bed-load layer. A simple expression specifying the bed-load concentration as a function of the flow and sediment conditions is proposed. A verification analysis using about 600 (alternative) data shows that about 77% of the predicted bed-load-transport rates are within 0.5 and 2 times the observed values.
1,653 citations
TL;DR: In this article, a method is presented which enables the computation of the suspended load as the depth-integration of the product of the local concentration and flow velocity, based on the calculation of the reference concentration from the bed-load transport.
Abstract: A method is presented which enables the computation of the suspended load as the depth-integration of the product of the local concentration and flow velocity. The method is based on the computation of the reference concentration from the bed-load transport. Measured concentration profiles have been used for calibration. New relationships are proposed to represent the size gradation of the bed material and the damping of the turbulence by the sediment particles. A verification analysis using about 800 data shows that about 76% of the predicted values are within 0.5 and 2 times the measured values.
1,564 citations
TL;DR: In this article, the relationship of sediment transport to fluid flow is considered and predictive equations are derived which relate total sediment flux to measurable properties of flow, and a preliminary comparison is made with observations from other sources, including natural rivers.
Abstract: The relationship of sediment transport to fluid flow is considered. Physical reasoning leads to dimensionless groupings of the variables which are different for coarse sediment and for fine sediment, because of dissimilar modes of transport. This concept provides a basis for a new analysis of data from flume experiments, and a method for dealing with transitional sizes of sediment is suggested. The analysis of experimental data supports the theory put forward and predictive equations are derived which relate total sediment flux to measurable properties of flow. A preliminary comparison is made with observations from other sources, including natural rivers.
932 citations
TL;DR: In this article, an analytic model of free-surface flow over an erodible bed is developed and used to investigate the stability of the fluid-bed interface and the characteristics of the bed features.
Abstract: An analytic model of free-surface flow over an erodible bed is developed and used to investigate the stability of the fluid-bed interface and the characteristics of the bed features. The model is based on the potential flow over a two-dimensional, moving, wavy bed with a sinusoidal profile of varying amplitude, and a sediment transport relation in which the transport rate is proportional to a power of the fluid velocity at the level of the bed. By assuming that the dominant wavelength is that for which the rate of amplitude growth is the greatest, expressions are obtained for the wavelength and velocity of the bed features. In addition, conditions for the occurrence of the different configurations, dunes, flat bed, and antidunes, are found from the model. The predicted wavelengths of antidunes and ranges of wavelengths of dunes, and the predicted conditions for change of bed configuration are found to be in good agreement with experimental data. Finally, brief consideration is given to the factors involved in determining the maximum heights of the bed features and surface waves.
598 citations
TL;DR: In this article, the length and height of the sand-waves are calculated using the value of the grain-size Reynolds number, which is a simple mathematical form and can be easily used in engineering practice for the prediction of the size of irregularities of a mobile bed.
Abstract: Formulas for the calculation of the length and height of the sand-waves are suggested. These formulas are valid for steady and uniform turbulent flow and for cohesionless bed material. The judgement as to whether sand-waves are ripples or dunes is made according to the value of the grain-size Reynolds number. The suggested formulas have an extremely simple mathematical form and can, therefore, be easily used in engineering practice for the prediction of the size of irregularities of a mobile bed. The formulas were determined from a wide range of experimental data obtained from both laboratory flumes and rivers. The experimental data used covers the range of grain-sizes 0.085 mm to 2.45 mm, and the range of water depths 1.32 cm to 92.5 ft.
269 citations