An entrainment model for non‐uniform sediment

A model was developed for the prediction of the entrainment rate of non-uniform sediment considering the movement of bedforms. Laboratory experiments were conducted to advance the formulations of the proposed model and to validate and estimate the model parameters. The model parameters were related to the hydraulic conditions of the flow and the properties of the sediment mixtures using dimensional analysis and gene expression programming. The model incorporated four parameters on its formulation, namely the Shields stress and critical Shields stress to describe the hydraulic and sediment conditions of the flow, the Kramer coefficient of uniformity to describe the grain size distribution of a particular sediment mixture, and the relative position of a particular grain size fraction to the geometric mean to describe the entrainment rate of that fraction within the sediment mixture. The proposed model provided satisfactorily predictions with a deviation less than 25% between the measured and predicted values for most of the fractions, which confirms the validity of the proposed approach and model in predicting of the entrainment rates of various fractions. The model predictions were also compared with other models available for the prediction of the entrainment rate of non-uniform sediment. The model predictions were within the same order of magnitude of the other models’ predictions. Copyright © 2015 John Wiley & Sons, Ltd.

[1]  A. Badoux,et al.  The impact of exceptional events on erosion, bedload transport and channel stability in a step‐pool channel , 2009 .

[2]  J. Imran,et al.  Density Functions for Entrainment and Deposition Rates of Uniform Sediment , 2007 .

[3]  S. Mclean.  Depth‐Integrated Suspended‐Load Calculations , 1991 .

[4]  Predicting the equilibrium bed slope in natural streams using a stochastic model for incipient sediment motion , 2011 .

[5]  Albert Molinas,et al.  Comparison of fractional bed-material load computation methods in sand-bed channels. , 2000 .

[6]  A. Hunt,et al.  Tests of predicted downstream transport of clasts in turbulent flow , 2003 .

[7]  D. B. Simons,et al.  Summary of alluvial channel data from flume experiments, 1956-61 , 1966 .

[8]  D. B. Simons,et al.  Resistance to Flow in Alluvial Channels , 1960 .

[9]  Z. Cao.  Turbulent Bursting-Based Sediment Entrainment Function , 1997 .

[10]  R. J. Garde,et al.  Bed-material characteristics of alluvial streams , 1972 .

[11]  H. Einstein,et al.  The Bed-Load Function for Sediment Transportation in Open Channel Flows , 1950 .

[12]  Jørgen Fredsøe,et al.  Data analysis of bed concentration of suspended sediment , 1994 .

[13]  Subhash C. Jain.  Note on Lag in Bedload Discharge , 1992 .

[14]  S. Mclean.  On the calculation of suspended load for noncohesive sediments , 1992 .

[15]  Greg . Smith,et al.  Modelling hydrodynamics in the Rio Parana, Argentina : an evaluation and inter-comparison of reduced-complexity and physics based models applied to a large sand-bed river , 2012 .

[16]  I. McEwan,et al.  Discrete Particle Modeling of Entrainment from Flat Uniformly Sized Sediment Beds , 2001 .

[17]  Jørgen Fredsøe,et al.  A Sediment Transport Model for Straight Alluvial Channels , 1976 .

[18]  Marcelo Horacio Garcia,et al.  Entrainment of Bed Sediment into Suspension , 1991 .

[19]  Ahmed M. A. Sattar,et al.  Gene expression models for prediction of dam breach parameters , 2014 .

[20]  P. Diplas,et al.  Surface roughness effects in near-bed turbulence: Implications to sediment entrainment , 2001 .

[21]  Giulia Garegnani,et al.  On the range of validity of the Exner-based models for mobile-bed river flow simulations , 2013 .

[22]  H. Md. Azamathulla,et al.  Gene-Expression Programming for Sediment Transport in Sewer Pipe Systems , 2011 .

[23]  Tarek M. Mostafa,et al.  Local scour at bridge abutments in cohesive soil , 2012 .

[24]  G. Parker.  Transport of Gravel and Sediment Mixtures , 2013 .

[25]  Prabhata K. Swamee,et al.  Bed-Load and Suspended-Load Transport of Nonuniform Sediments , 1991 .

[26]  Peter B. Hairsine,et al.  Spatial evaluation of a multi‐class sediment transport and deposition model , 2004 .

[27]  Paola Gramatica,et al.  The Importance of Being Earnest: Validation is the Absolute Essential for Successful Application and Interpretation of QSPR Models , 2003 .

[28]  L. Bracken,et al.  Understanding sediment transfer and morphological change for managing upland gravel-bed rivers , 2010 .

[29]  S. R. McLean,et al.  Spatially averaged flow over a wavy surface , 1977 .

[30]  Kelvin J. Richards,et al.  The formation of ripples and dunes on an erodible bed , 1980, Journal of Fluid Mechanics.

[31]  C. S. James.  Prediction of entrainment conditions for nonuniform, noncohesive sediments , 1990 .

[32]  S. Wright,et al.  Flow Resistance and Suspended Load in Sand-Bed Rivers: Simplified Stratification Model , 2004 .

[33]  J. R. Allen.  Sedimentation to the Lee of Small Underwater Sand Waves: An Experimental Study , 1965, The Journal of Geology.

[34]  C. Kranenburg,et al.  Reducing the siltation of a river harbour , 1998 .

[35]  Matthew D. Grace,et al.  Advances in sediment transport modelling , 2010 .

[36]  A. Sukhodolov.  Hydrodynamics of groyne fields in a straight river reach: insight from field experiments , 2014 .

[37]  Van Rijn,et al.  Sediment transport; Part I, Bed load transport , 1984 .

[38]  J. Warwick,et al.  The effect of magnetic topography on high-latitude radio emission at Neptune , 1992 .

[39]  George A. Krallis,et al.  Sediment Transport Modeling Review—Current and Future Developments , 2008 .