scholarly journals SUSPENDED SEDIMENT CONCENTRATION IN THE SURF ZONE

1988 ◽  
Vol 1 (21) ◽  
pp. 123 ◽  
Author(s):  
Makoto Ifuku ◽  
Tadao Kakinuma
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Surf Zone ◽  
Diffusion Theory ◽  
Sediment Concentration ◽  
Finite Amplitude ◽  
Reference Level ◽  
Sand Particle ◽  
Phase Lag ◽  
Mean Values

The water particle velocity,the pressure fluctuation and suspended sediment concentration near the bottom were measured in the surf zone. Data were obtained on the mean sediment concentration, phase lag between onshore velocity and suspended sediment concentration. The near-bottom velocity distributions under finite amplitude waves were calculated on the basis of the turbulent boundary layer theory by using timeindependent/ dependent eddy viscosities and Prandtl mixing length theory. The concentrations at reference level were estimated from the Kalkanis' theory using the velocity value at the top of a sand particle and the distributions of suspended sediment concentration were calculated on the basis of the turbulent diffusion theory by using time-independent/ dependent diffusion coefficients. The computed mean values of the suspended sediment concentration agree with those observed by Noda, the authors and Nielsen and those measured by Deigaard et al.. The computed phase lag agrees well with observed by the authors.

scholarly journals Surf Zone Turbulence and Suspended Sediment Dynamics—A Review

2021 ◽  
Vol 9 (11) ◽  
pp. 1300
Author(s):  
Troels Aagaard ◽  
Joost Brinkkemper ◽  
Drude F. Christensen ◽  
Michael G. Hughes ◽  
Gerben Ruessink
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Surf Zone ◽  
Sediment Concentration ◽  
Sandy Beaches ◽  
Suspended Sediment Transport ◽  
Velocity Signal ◽  
Wave Phase ◽  
Turbulence Production

The existence of sandy beaches relies on the onshore transport of sand by waves during post-storm conditions. Most operational sediment transport models employ wave-averaged terms, and/or the instantaneous cross-shore velocity signal, but the models often fail in predictions of the onshore-directed transport rates. An important reason is that they rarely consider the phase relationships between wave orbital velocity and the suspended sediment concentration. This relationship depends on the intra-wave structure of the bed shear stress and hence on the timing and magnitude of turbulence production in the water column. This paper provides an up-to-date review of recent experimental advances on intra-wave turbulence characteristics, sediment mobilization, and suspended sediment transport in laboratory and natural surf zones. Experimental results generally show that peaks in the suspended sediment concentration are shifted forward on the wave phase with increasing turbulence levels and instantaneous near-bed sediment concentration scales with instantaneous turbulent kinetic energy. The magnitude and intra-wave phase of turbulence production and sediment concentration are shown to depend on wave (breaker) type, seabed configuration, and relative wave height, which opens up the possibility of more robust predictions of transport rates for different wave and beach conditions.

scholarly journals Appraisal of suspended sediment concentration on reference level according to van Rijn's method

2008 ◽  
Vol 40 (1) ◽  
pp. 67-76
Author(s):  
Bogusław Michalec
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Reference Level ◽  
Concentration Profiles ◽  
It Adoption ◽  
Vistula River ◽  
Preliminary Estimation

Appraisal of suspended sediment concentration on reference level according to van Rijn's method Appraisal of suspended sediment concentration on reference level according to van Rijn's method. The paper presents the results of sediment concentration measurements in the River Dłubnia at differentiated discharges of 0.44 m-3·s-1, 1.96 m-3·s-1 and 7.41 m-3·s-1. The elaborated concentration profiles based on hydrometric measurements permitted determination of Ca concentration on reference level "a" above the bed. The obtained reference concentrations were compared with the values obtained from calculations by use of van Rijn's formula. It was found that the calculated Ca concentration, applying the van Rijn's formula, is over five times higher than determined from concentration profiles. In order to obtain Ca concentration values, calculated by use of the empiric formula, approximate to real values coefficient correction must be determined. The elaborated preliminary estimation of the possibility of van Rijn's formula application for determination of this concentration on the reference level "a" above the bed showed that application of this method for appraisal of Ca concentration, by use van Rijn's formula, performed in the Dłubnia river of the catchment of the Upper Vistula river may be charged by errors. A faulty calculation of suspension sediment transport applying van Rijn's method may also point to it. Adoption of this method needs further verification and adaptation.

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 An Assimilation Simulation Approach to Suspended Sediment Concentration in Inland Lakes Using Hybrid Perturbation Generation Method

2021 ◽  
Author(s):  
Fei Guo ◽  
Jingjia Zhang ◽  
A-xing Zhu ◽  
Zhuo Zhang ◽  
Hong Zhang
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Random Perturbation ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Hydrological Simulation ◽  
Simulation Accuracy ◽  
Mean Values ◽  
Inland Lakes ◽  
Perturbation Field

Abstract Suspended sediments, as one of the most important factors affecting the water environment of inland lakes, are closely related to the various pollutants migration and interaction. Thus, the simulation and prediction of suspended sediment concentration is important. Existing studies show that the prediction accuracy of suspended sediment concentration can be effective predicted based on assimilation methods coupled with hydrodynamic models. However, in the process of assimilation of hydrological simulation, the existing perturbation generation methods consider that the perturbation error is a random Gaussian distribution, which does not consider the spatial variation characteristics of errors. In this paper, a new method to generate the perturbation field for assimilation simulation was proposed. This method uses hybrid error to generate perturbation field for assimilation simulation instead of using random error. The proposed approach was validated through its application to assimilation simulation of suspended sediment concentration of Taihu Lake in China, and five assimilation experiments was conducted. The proposed method was compared with existing methods for perturbation field generation. After three days and 72 time steps of assimilation simulation based on hybrid perturbation generation, we found that the proposed assimilation method provided results that were more consistent with buoy-measured data. The accuracy of the two assimilation methods based on hybrid perturbation is improved. Compared with the assimilation method based on random perturbation, the mean values of RMSE(root mean square error) decreased from 9.56 to 8.70 and from 9.55 to 8.68, respectively. The results show that the proposed hybrid perturbation generation method has higher simulation accuracy than other methods. This study shows that the method is effective and provides a new idea for the assimilation simulation of suspended sediment concentration in inland lakes.

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