scholarly journals ON-OFFSHORE SEDIMENT TRANSPORT RATE IN THE SURF ZONE

1980 ◽  
Vol 1 (17) ◽  
pp. 72 ◽  
Author(s):  
Toru Sawaragi ◽  
Ichiro Deguchi
Keyword(s):  
Sediment Transport ◽  
Surf Zone ◽  
Suspended Load ◽  
Transport Rate ◽  
Bed Load ◽  
Relative Importance ◽  
Two Dimensional ◽  
Sediment Transport Rate

In this paper, models of the distribution of net on-offshore sediment transport based on two-dimensional equilibrium beach profiles and an equation of continuity of sediment transport are proposed. Various parameters of net on-offshore sediment transport in those models are discussed. Furhter, the relative importance of bed load and suspended load in the two-dimensional beach deformation are examined by measuring both of them on model beach experiments.

scholarly journals CALCULATION OF THE RATE OF NET ON-OFFSHORE SEDIMENT TRANSPORT ON THE BASIS OF FLUX CONCEPT

1984 ◽  
Vol 1 (19) ◽  
pp. 91 ◽  
Author(s):  
Ichiro Deguchi ◽  
Toru Sawaragi
Keyword(s):  
Sediment Transport ◽  
Water Depth ◽  
Sediment Concentration ◽  
Suspended Load ◽  
Spatial Variations ◽  
Sediment Flux ◽  
Bed Load ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Two Dimensional Model

Time and spatial variations of sediment concentration of both bed load and suspended load in the process of two-dimensional beach deformation were investigated experimentally. At the same time, the relation between the velocities of water-particle and sediment migration was analyzed theoretically. By using those results,a net rate of on-offshore sediment_ transport in the process of two-dimensional model beach deformation qf was calculated on the basis of sediment flux. It is found that Qf coincides fairly well with .the net rate of on-offshore sediment transport calculated from the change of water depth.

scholarly journals OBSERVATIONS OF HORIZONTAL AND VERTICAL SEDIMENT FLUXES ON A SANDBAR IN THE SUSPENDED AND SHEET FLOW LAYERS

2018 ◽  
pp. 30
Author(s):  
Ryan S. Mieras ◽  
Jack A. Puleo ◽  
Dylan Anderson ◽  
Daniel T. Cox ◽  
Tian-Jian Hsu ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Surf Zone ◽  
Breaking Waves ◽  
Suspended Load ◽  
Bed Load ◽  
Sheet Flow ◽  
Coastal Morphology ◽  
Sediment Fluxes ◽  
Wave Forcing ◽  
Transport Component

The majority of prior sandbar migration studies have been conducted from the morphological standpoint, whereby, (i) bathymetric profiles are recorded over periods of time ranging from days to decades, at frequencies ranging from hourly to yearly (Ruessink et al., 2003), and (ii) hydrodynamic observations typically consist of far-field wave and environmental conditions. Subsequent modeling efforts have generally focused on tuning parameters in the sediment transport formulations (suspended load and bed load) to maximize model skill in predicting observed beach profiles over time (Fernández-Mora et al., 2015; Hoefel and Elgar, 2003). However, little emphasis at the operational level has been placed on tuning coastal morphology models to the true relative contributions of the physical processes (e.g. suspended load, bed load and/or sheet flow) that drive the changing bathymetry. This is due, in part, to the lack of detailed sediment transport observations (field and lab) under realistic wave forcing conditions and spatially variable bathymetry. Such a modeling approach leads to the improper quantification (magnitude and/or direction) of each modeled sediment transport component under skewed-asymmetric and/or breaking waves, often observed in the surf zone. The present study aims to better understand the physical mechanisms responsible for driving cross-shore sediment transport over a sandbar by quantifying (a) the vertical exchange of sediment at the near-bed interface (i.e. pick-up layer), and (b) intra-wave horizontal sediment fluxes in the suspended load and sheet layers.

scholarly journals BED LOAD TRANSPORT DUE TO NON-LINEAR WAVE MOTION

1988 ◽  
Vol 1 (21) ◽  
pp. 133 ◽  
Author(s):  
Hitoshi Tanaka
Keyword(s):  
Sediment Transport ◽  
Wave Motion ◽  
Surf Zone ◽  
Function Theory ◽  
Transport Rate ◽  
Bed Load ◽  
Linear Wave ◽  
Wave Flume ◽  
Load Transport ◽  
Bed Load Transport

The bed load transport rate due to wave motion is measured in a wave flume. The modified stream function theory of the author ( Tanaka (1988) ) is applied to the formulation of the sediment transport rate in order to include the non-linearity. The proposed formula predicts well except near the surf zone where the effect of the acceleration plays an important role.

Bed Load Transport under Complex Flow

2011 ◽  
Vol 255-260 ◽  
pp. 3589-3593
Author(s):  
Chun Rong Liu ◽  
Dao Lin Xu
Keyword(s):  
Sediment Transport ◽  
Time History ◽  
Shear Velocity ◽  
Transport Rate ◽  
Bed Load ◽  
Complex Flow ◽  
Sediment Transport Rate ◽  
Load Transport ◽  
History Of ◽  
Load Sediment

In this paper, the backward-facing step flow and the sediment transport downstream step were studied experimentally. The critical incipient bed shear velocity is obtained by the results of bed shear velocity and sediment incipient probability. It was found that the critical incipient bed shear velocity depends on the flow structures under the complex flow. By using the new critical incipient bed shear obtained in this paper and calculating the Shields parameter based on instantaneous bed shear velocity, the bed load sediment transport rate downstream step was given. The time history of the bed profile downstream step was calculated by bed load sediment transport rate and compared that obtained by the digital images. Good agreement was observed.

scholarly journals Experimental Study on Uniform and Mixed Bed-Load Sediment Transport under Unsteady Flow

2020 ◽  
Vol 10 (6) ◽  
pp. 2002
Author(s):  
Zihao Duan ◽  
Jie Chen ◽  
Changbo Jiang ◽  
Xiaojian Liu ◽  
Bingbing Zhao
Keyword(s):  
Particle Size ◽  
Sediment Transport ◽  
Unsteady Flow ◽  
Steady Flow ◽  
Transport Rate ◽  
Bed Load ◽  
Sediment Transport Rate ◽  
Particle Size Ratio ◽  
Load Movement ◽  
Sediment Particles

The scouring and deposition of sediment caused by unsteady flows (e.g., storm waves and floods) produces many secondary disasters. The resultant bed-load movement exhibits different transport laws compared with that by steady flow. In this study, the flume experiments were performed to study the bed-load movement under unsteady flow with different velocity skewness. The movement of uniform and non-uniform non-cohesive sediment under unsteady flow as well as the influence of the steady and unsteady flow on sediment transport rate are compared. Additionally, the non-uniform sediment transport formula of fine-to-coarse particle diameter ratio was investigated. The results showed that the sediment transport rate between uniform and non-uniform sand under the same median diameter is different. The non-uniform sediment transport rate is 1.27-, 3.19-, and 0.68-times as large as that in uniform sediment under d50 = 0.664, 1.333, and 2.639 mm under unsteady flow, respectively. For non-uniform sand, the transport rate of non-uniform sand with a larger adjacent particle size ratio (δ = 0.29) was 1.31-times greater than that of the non-uniform sand with a smaller adjacent particle size ratio (δ = 0.50). Moreover, theoretical deduction was carried out and the incipient sediment motion was analyzed from the force mechanism. A new unsteadiness parameter based on the acceleration concept was proposed. The relationship between the travel distance and velocity skewness of sediment particles was set up. The experimental results and theoretical analysis showed that sediment under unsteady flow were easier to start and transport than those under steady flow in the same flow effect. The travel distance of sediment particles was longer under unsteady flow than that under steady flow.

scholarly journals FIELD STUDY ON ON SHORE-OFFSHORE SEDIMENT TRANSPORT

1982 ◽  
Vol 1 (18) ◽  
pp. 58 ◽  
Author(s):  
Masataro Hattori
Keyword(s):  
Sediment Transport ◽  
Surf Zone ◽  
Transport Rate ◽  
Data Set ◽  
Sediment Transport Rate ◽  
Sea Bottom ◽  
Field Investigations ◽  
Transport Direction ◽  
Sand Movement ◽  
Wave Induced

The mechanism of onshore-offshore sediment transport and the process of beach profile evolution were studied through field investigations performed at Oarai Beach, Japan. The principal data set consists of twenty-four profile surveys taken at hourly intervals on each of two parallel lines spaced 10 m apart and of length 150 m. The lines extended from the backshore of the beach to a point on the sea bottom at a depth where no sand movement occurred. Simultaneous measurements of the waves and wave-induced currents were also made; the essential requirement of two-dimensionality was found to hold during the experiment. The profiles were used to calculate the net sediment transport rate on-offshore, and for an empirical eigenfunction analysis. A negative correlation was found between the transport direction (and resultant bottom change) and the mean sea level change. The sediment transport rate in the foreshore region was found to be proportional to the wave power, whereas outside the surf zone and near the breaker position it was proportional to the tractive force.

scholarly journals A MULTIPLE-SIZED TRANSPORT FORMULA FOR NONUNIFORM SEDIMENTS UNDER CURRENT AND WAVES

2012 ◽  
Vol 1 (33) ◽  
pp. 34 ◽  
Author(s):  
Weiming Wu ◽  
Qianru Lin
Keyword(s):  
Shear Stress ◽  
Sediment Transport ◽  
Size Composition ◽  
Suspended Load ◽  
Transport Rate ◽  
Bed Load ◽  
Nonuniform Sediment ◽  
Load Transport ◽  
Bed Load Transport ◽  
Bed Material

Nonuniform sediment transport exhibits difference from uniform sediment, even when the mean grain size is the same for both cases. The hiding, exposure, and armoring among different size fractions in the nonuniform bed material may significantly affect sediment transport, morphological change, bed roughness, wave dissipation, etc. It is necessary to develop multiple-sized sediment transport capacity formula to improve the accuracy and reliability of coastal analysis tools. The Wu et al. (2000) formula, which was developed for river sedimentation, is herein extended to calculate multiple-sized sediment transport under current and waves for coastal applications. This formula relates bed-load transport to the grain shear stress and suspended-load transport to the energy of the flow system. It considers the effect of bed material size composition in the hiding and exposure correction factor, which is omitted in many other existing formulas. Methods have been developed in this study to determine the bed shear stress due to waves only and combined current and waves, and in turn to compute the bed-load and suspended-load transport rates using the Wu et al. (2000) formula without changing its original formulation. The enhanced bed-load formula considers the effect of wave asymmetry on sediment transport, calculates the onshore and offshore bed-load transport rates separately and then derives the net transport rate, whereas the enhanced suspended-load formula calculates only the net transport rate due to the limit of available data. The formula has been tested using the single-sized and multiple-sized sediment transport data sets. The formula provides reliable predictions in both fractional and total transport rates. More than half of the test cases are predicted within a factor of 2 of the measured values, and more than 90% of the cases are within a factor of 5. This accuracy is generally reasonable for sediment transport under current and waves, which is very complex and little understood.

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