scholarly journals Vertical Distribution of Suspended Sediment under Steady Flow: Existing Theories and Fractional Derivative Model

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Shiqian Nie ◽  
HongGuang Sun ◽  
Yong Zhang ◽  
Dong Chen ◽  
Wen Chen ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Turbulent Flow ◽  
Fractional Derivative ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Advection Diffusion Equation ◽  
The Vertical Distribution ◽  
Sediment Settling ◽  
Derivative Order

The fractional advection-diffusion equation (fADE) model is a new approach to describe the vertical distribution of suspended sediment concentration in steady turbulent flow. However, the advantages and parameter definition of the fADE model in describing the sediment suspension distribution are still unclear. To address this knowledge gap, this study first reviews seven models, including the fADE model, for the vertical distribution of suspended sediment concentration in steady turbulent flow. The fADE model, among others, describes both Fickian and non-Fickian diffusive characteristics of suspended sediment, while the other six models assume that the vertical diffusion of suspended sediment follows Fick’s first law. Second, this study explores the sensitivity of the fractional index of the fADE model to the variation of particle sizes and sediment settling velocities, based on experimental data collected from the literatures. Finally, empirical formulas are developed to relate the fractional derivative order to particle size and sediment settling velocity. These formulas offer river engineers a substitutive way to estimate the fractional derivative order in the fADE model.

scholarly journals Fractal derivative model for the transport of the suspended sediment in unsteady flows

2018 ◽  
Vol 22 (Suppl. 1) ◽  
pp. 109-115 ◽  
Author(s):  
Shiqian Nie ◽  
Hong Sun ◽  
Xiaoting Liu ◽  
Wang Ze ◽  
Mingzhao Xie
Keyword(s):  
Vertical Distribution ◽  
Unsteady Flow ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Spatial Location ◽  
Sediment Concentration ◽  
Equation Model ◽  
Advection Dispersion ◽  
Fractal Derivative ◽  
The Vertical Distribution

This paper makes an attempt to develop a Hausdorff fractal derivative model for describing the vertical distribution of suspended sediment in unsteady flow. The index of Hausdorff fractal derivative depends on the spatial location and the temporal moment in sediment transport. We also derive the approximate solution of the Hausdorff fractal derivative advection-dispersion equation model for the suspended sediment concentration distribution, to simulate the dynamics procedure of suspended concentration. Numerical simulation results verify that the Hausdorff fractal derivative model provides a good agreement with the experimental data, which implies that the Hausdorff fractal derivative model can serve as a candidate to describe the vertical distribution of suspended sediment concentration in unsteady flow.

scholarly journals Theoretical Model of Suspended Sediment Concentration in a Flow with Submerged Vegetation

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1656 ◽  
Author(s):  
Da Li ◽  
Zhonghua Yang ◽  
Zhaohua Sun ◽  
Wenxin Huai ◽  
Jianhua Liu
Keyword(s):  
Vertical Distribution ◽  
Suspended Sediment ◽  
Schmidt Number ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Submerged Vegetation ◽  
Distribution Profile ◽  
Turbulent Schmidt Number ◽  
Rouse Number ◽  
The Vertical Distribution

Vegetation in natural river interacts with river flow and sediment transport. This paper proposes a two-layer theoretical model based on diffusion theory for predicting the vertical distribution of suspended sediment concentration in a flow with submerged vegetation. The suspended sediment concentration distribution formula is derived based on the sediment and momentum diffusion coefficients through the inverse of turbulent Schmidt number ( S c t ) or the parameter η which is defined by the ratio of sediment diffusion coefficient to momentum diffusion coefficient. The predicted profile of suspended sediment concentration moderately agrees with the experimental data. Sensitivity analyses are performed to elucidate how the vertical distribution profile responds to different canopy densities, hydraulic conditions and turbulent Schmidt number. Dense vegetation renders the vertical distribution profile uneven and captures sediment particles into the vegetation layer. For a given canopy density, the vertical distribution profile is affected by the Rouse number, which determines the uniformity of the sediment on the vertical line. A high Rouse number corresponds to an uneven vertical distribution profile.

scholarly journals Numerical Simulation of the Sea Bottom Modifications Behind a T-head Groin

2020 ◽  
Vol 15 ◽  
Keyword(s):  
Diffusion Equation ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Surf Zone ◽  
Fluid Dynamic ◽  
Sediment Concentration ◽  
Breaking Wave ◽  
Advection Diffusion Equation ◽  
Advection Diffusion ◽  
Sea Bottom

In this paper, we simulate the sea bottom modifications produced by the presence of a T-head groin. We present a simulation model of sea bottom modifications composed of two sub-models: a two-dimensional phase-resolving model that simulate the variation of the fluid dynamic variables inside the wave; a second sub-model to simulate the sea bottom modifications, in which the suspended sediment concentration is calculated by the wave-averaged advection-diffusion equation. The fluid motion equation and the concentration equation are expressed in a new contravariant formulation. The velocity fields from deep water up to just seaward of the surf-zone are simulated by a new integral contravariant form of the Fully Nonlinear Boussinesq Equations. The new integral form of the proposed continuity equation does not contain the dispersive term. The Nonlinear Shallow Water Equations, expressed in an integral contravariant form, are solved in order to simulate the breaking wave propagation. The momentum equation, integrated over the turbulent boundary layer, is solved to calculate the near-bed instantaneous flow velocity and the intra-wave hydrodynamic quantities. Starting from the contravariant formulation of the advection–diffusion equation for the suspended sediment concentration, it is possible to calculate the sea bottom modification. The advective sediment transport terms in the advection-diffusion equation are formulated according to a quasi-three-dimensional approach

scholarly journals LAGRANGIAN DROGUE-BASED DRIFTER FOR MONITORING SUSPENDED SEDIMENT TRANSPORT IN INTERTIDAL ENVIRONMENTS

2011 ◽  
Vol 1 (32) ◽  
pp. 81
Author(s):  
Takahiro Nishi ◽  
Charles Lemckert ◽  
Kentaro Hayashi ◽  
Fumihiko Yamada
Keyword(s):  
Suspended Sediment ◽  
Current Velocity ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Spatial Distributions ◽  
Flow Conditions ◽  
Current Profile ◽  
Directional Flow ◽  
Temporal And Spatial ◽  
Sediment Settling

The in-situ Lagrangian-Acoustic Drogue (LAD) presented by Schacht and Lemckert (2007) for monitoring the temporal and spatial distributions of both the current and the suspended sediment concentration within the estuary environments has been modified to operate in the shallow water intertidal regions. The new drogue, called the LAD for Inter-Tidal environments (LAD-IT), is equipped with a Global Positioning System (GPS), a small Acoustic Doppler Current Profiler (ADCP) and nephelometer. The small ADCP, which did not have a bottom tracking facility, was used to maximize the range of depths the LAD-IT could operate over. The accuracy of a vertical current profile measured using the LAD-IT was examined through the laboratory experiments conducted at an outdoor stream pool in Kumamoto, Japan, with uni-directional flow conditions, and through the field experiments conducted within an intertidal zone of Ariake Sound in Kumamot, Japan, with multi-directional flow conditions. Under uni- directional flow conditions the current profile was measured within 7% accuracy by summing the surface current velocity calculated using GPS tracking and the relative current profile measured using ADCP. Under multi-directional flow conditions, such as those of tide and wind-induced wave fields, the current profile agreed within 5% accuracy. This was partly because both Eulerian and Lagrangian mass transport velocities under these conditions were on the order of 1cm/s, and thus the error value was very small. The temporal and spatial distributions of both the current velocity and the suspended sediment concentration were also measured using the LAD-IT on the Brisbane River, Australia under uni-directional flow conditions. The field observation results support the conventional concept of the suspended sediment as a vertical balance between downward suspended sediment settling and upward turbulent diffusion fluxes. The results indicate the LAD-IT is adequate for estimating the sediment settling velocity in the field.

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