High sediment concentration layer of fine sediments: Modelling by a 1DV model

2018 ◽  
pp. 67-109
Author(s):  
Liqin Zuo
Keyword(s):  
Sediment Concentration ◽  
Fine Sediments ◽  
Concentration Layer ◽  
High Sediment

scholarly journals Formation of Oil-Particle-Aggregates: Numerical Model Formulation and Calibration

2021 ◽  
Vol 8 ◽  
Author(s):  
Linlin Cui ◽  
Courtney K. Harris ◽  
Danielle R. N. Tarpley
Keyword(s):  
Fractal Dimension ◽  
Size Distribution ◽  
Sediment Concentration ◽  
River Plume ◽  
Model Parameters ◽  
Dimensional Model ◽  
Outer Continental Shelf ◽  
Collision Efficiency ◽  
Particle Aggregates ◽  
High Sediment

When oil spills occur in turbid waters, the oil droplets and mineral grains can combine to form oil-particle aggregates (OPAs). The formation of OPAs impacts the vertical transport of both the oil and the mineral grains; especially increasing deposition of oil to the seabed. Though the coastal oceans can be very turbid, to date, few numerical ocean models have accounted for aggregation processes that form OPAs. However, interactions between oil and mineral aggregates may be represented using techniques developed to account for sediment aggregation. As part of Consortium for Simulation of Oil Microbial Interactions in the Ocean (CSOMIO), we modified an existing, population dynamics-based sediment flocculation model to develop OPAMOD, a module that accounts for the formation of OPAs. A zero-dimensional model using OPAMOD is shown to be capable of reproducing the size distribution of aggregates from existing laboratory experimental results. Also using the zero-dimensional model, sensitivity tests were performed on two model parameters, the fractal dimension and collision efficiency. Results showed that fractal dimension played a role in the OPA size distribution by influencing the effective particle density, which modified the number concentration of flocs for a given mass concentration. However, the modeled particle characteristics and oil sequestration were relatively insensitive to collision efficiency. To explore OPA formation for an outer continental shelf site, two simulations were conducted using a one-dimensional (vertical) implementation of the model. One scenario had high sediment concentration near the seabed to mimic storm-induced resuspension. The other scenario represented river plume sediment delivery by having high sediment concentration in surface waters. Results showed that OPA formation was sensitive to the vertical distribution of suspended sediment, with the river plume scenario creating more OPA, and sequestering more oil within OPA than the storm resuspension scenario. OPAMOD was developed within the Coupled Ocean-Atmosphere-Wave-and-Sediment Transport (COAWST) modeling system, therefore the methods and parameterizations from this study are transferrable to a three-dimensional coupled oil-sediment-microbial model developed by CSOMIO within the COAWST framework.

scholarly journals Hydrogeology of Volcanic Highlands Affects Prioritization of Land Management Practices

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2702 ◽  
Author(s):  
Anwar A. Adem ◽  
Gashaw G. Addis ◽  
Dessalew W. Aynalem ◽  
Seifu A. Tilahun ◽  
Wolde Mekuria ◽  
...  
Keyword(s):  
Water Management ◽  
Soil Degradation ◽  
Management Practices ◽  
Potable Water ◽  
Water Source ◽  
Sediment Concentration ◽  
Agricultural Watershed ◽  
Land And Water Management ◽  
High Sediment ◽  
Tertiary Basalt

Volcanic highlands supply water to 40% of the world’s population. Soil degradation threatens this water supply. Studies on geohydrology that affect the effectiveness of land and water management (LWM) practices in reducing soil degradations are limited. To aid in the effectiveness of LWM practices, we conducted a field experiment in the Gomit watershed in the semihumid Ethiopian Highlands on the interaction of hydrogeology and LWM practices. We found that in a watershed with strongly faulted tertiary basalt, 30% of the rainfall was drained through faults to another basin. Consequently, the discharge at the outlet was less than half of that of other watersheds with quaternary basalts. Despite the high sediment concentration, i.e., around 15 g L−1, in the Gomit watershed, the sediment yield of less than 4 Mg ha−1 a−1 was below average for the agricultural watershed in Ethiopia because of the low runoff response. While some faults facilitated drainage, others acted as a barrier. Groundwater stored behind the barriers was used as a municipal potable water source. Since the effectiveness of LWM practices depends on the amount of erosion that can be prevented, considerations of country-wide prioritizing of investments in land and water management practices should include the geology of the watersheds.

scholarly journals Influence of lateral embayments on suspended sediment transport under unsteady flow conditions

2018 ◽  
Vol 40 ◽  
pp. 03017 ◽  
Author(s):  
Carmelo Juez ◽  
Matthias Thalmann ◽  
Anton J. Schleiss ◽  
Mário J. Franca
Keyword(s):  
Water Discharge ◽  
Phase Fluctuation ◽  
Sediment Concentration ◽  
High Flow ◽  
Experimental Investigations ◽  
Suspended Sediment Transport ◽  
Fine Sediments ◽  
Sediment Deposits ◽  
Fluctuation Phase ◽  
Flow Phase

Local widening in a channelized river is a common practice in restoration projects. The lateral embayments built for this purpose in the river banks are partially filled up by fine sediments. This allows the formation of aquatic habitats with hydraulic and morphologic diversity. However, the design of these lateral cavities may be compromised by the fluctuations in the water discharge. To address this problem, systematic experimental investigations have been carried out with five different fluctuating hydrograph scenarios. Water depth, sediment concentration and area covered by the settled sediments are analysed in each experiment. The process of sedimentation in the lateral embayments proved to be, in general, resilient to flow fluctuations. However, there were several differences observed during the high flow phase fluctuation phase depending on the geometric configuration of the embayments and the applied hydrograph: (i) a higher peak in discharge means that more sediments are resuspended and a complete remobilization of the in-cavity sediment deposits is possible. (ii) Long and short cavities are more resilient to high flow events than cavities with an intermediate length.

Depositional Process of Fine Sediments

1982 ◽  
Vol 14 (4-5) ◽  
pp. 175-184 ◽  
Author(s):  
T Kusuda ◽  
T Umita ◽  
K Koga ◽  
H Yorozu ◽  
Y Awaya
Keyword(s):  
Shear Stress ◽  
Particle Diameter ◽  
Critical Diameter ◽  
Sediment Concentration ◽  
Suspended Particles ◽  
Cohesive Sediments ◽  
Fine Sediments ◽  
Annular Flume ◽  
Depositional Process ◽  
Depositional Rate

The main purposes of this study were to investigate the depositional properties of the typical fine less-cohesive sediments in Japanese estuaries and bays and to make it possible to estimate the amount of deposition of the sediments. Suspended fine sediment concentration depends strongly on the shear stress and a critical particle diameter exists corresponding to a certain shear stress. The suspended particles larger than the critical diameter settle down proportionally to the concentration of particles. On the other hand, the suspended particles smaller than the critical diameter are held in water without settling. The depositional properties obtained from experiments make it possible to estimate the depositional rate and amount of the sediments. In the laboratory experiments on deposition, an annular flume with a ring and a channel was used.

Sedimentation in proglacial Sunwapta Lake, Alberta

1981 ◽  
Vol 18 (1) ◽  
pp. 81-93 ◽  
Author(s):  
Robert Gilbert ◽  
John Shaw
Keyword(s):  
Water Movement ◽  
Fine Sand ◽  
Sediment Concentration ◽  
Turbidity Currents ◽  
Canadian Rocky Mountains ◽  
Sedimentary Characteristics ◽  
Suspended Sediment Concentrations ◽  
Continuous Sedimentation ◽  
Lake Floor ◽  
High Sediment

The hydrologic and limnologic conditions of Sunwapta Lake, a small proglacial lake in the Canadian Rocky Mountains, were investigated with special reference to the sedimentology of this lake. Discharge and suspended sediment concentrations of the inflowing streams were measured to give estimates of sediment input. Distribution of large loads of fine glacial sediment is largely by an inflow- and wind-controlled circulation, which commonly fluctuates diurnally. The spatial distribution of sedimentation was determined by use of sediment-collecting pans placed on the lake bed. Turbidity currents are rare with only one event monitored in 2 years. This event was caused by a burst of highly sediment-charged inflow water. The rarity of turbidity currents is attributed to the high sediment concentration in the lake water, which results from the small size of the lake in relation to the inflow. Wind-generated water movement at the lake floor ranges from 0.0–0.03 m/s while the maximum recorded velocity of the turbidity currents was 0.32 m/s.Sedimentation rates are calculated and six cores from the lake bed, each containing sediment deposited over several years, are described. Although bedding and lamination are found in all cores, correlation between cores was not possible. Sedimentary characteristics are related to inflow and lake conditions: laminated and massive beds of medium to fine sand and silt are related to turbidity events, graded laminae in coarse and fine silt to diurnal variations in lake currents, and massive beds in silt to periods of continuous sedimentation without diurnal variation. Deformed beds result from subaqueous slumps.

scholarly journals Flocculation processes and sedimentation of fine sediments in the open annular flume – experiment and numerical modeling

2013 ◽  
Vol 1 (1) ◽  
pp. 437-481 ◽  
Author(s):  
I. Klassen ◽  
G. Hillebrand ◽  
N. R. B. Olsen ◽  
S. Vollmer ◽  
B. Lehmann ◽  
...  
Keyword(s):  
Experimental Data ◽  
Fractal Dimension ◽  
Sediment Transport ◽  
Process Model ◽  
Settling Velocity ◽  
Numerical Models ◽  
Sediment Concentration ◽  
Small Scale ◽  
Fine Sediments ◽  
Aggregation Processes

Abstract. The prediction of cohesive sediment transport requires numerical models which include the dominant physico-chemical processes of fine sediments. Mainly in terms of simulating small scale processes, flocculation of fine particles plays an important role since aggregation processes affect the transport and settling of fine-grained particles. Flocculation algorithms used in numerical models are based on and calibrated using experimental data. A good agreement between the results of the simulation and the measurements is a prerequisite for further applications of the transport functions. In this work, the sediment transport model (SSIIM) was extended by implementing a physics-based aggregation process model based on McAnally (1999). SSIIM solves the Navier-Stokes-Equations in a three-dimensional, non-orthogonal grid using the k-ε turbulence model. The program calculates the suspended load with the convection-diffusion equation for the sediment concentration. Experimental data from studies in annular flumes (Hillebrand, 2008; Klassen, 2009) is used to test the flocculation algorithm. Annular flumes are commonly used as a test rig for laboratory studies on cohesive sediments since the flocculation processes are not interfered with by pumps etc. We use the experiments to model measured floc sizes, affected by aggregation processes, as well as the sediment concentration of the experiment. Within the simulation of the settling behavior, we use different formulas for calculating the settling velocity (Stokes, 1850 vs. Winterwerp, 1998) and include the fractal dimension to take into account the structure of flocs. The aim of the numerical calculations is to evaluate the flocculation algorithm by comparison with the experimental data. The results from these studies have shown, that the flocculation process and the settling behaviour are very sensitive to variations in the fractal dimension. We get the best agreement with measured data by adopting a characteristic fractal dimension nfc to 1.4. Insufficient results were obtained when neglecting flocculation processes and using Stokes settling velocity equation, as it is often done in numerical models which do not include a flocculation algorithm. These numerical studies will be used for further applications of the transport functions to the SSIIM model of reservoirs of the Upper Rhine River, Germany.

scholarly journals Laboratory Measurement of High Sediment Concentration with Light Extinction Method

2008 ◽  
Vol 55 ◽  
pp. 1436-1440 ◽  
Author(s):  
Takenori SHIMOZONO ◽  
Atsushi SASAKI ◽  
Akio OKAYASU ◽  
Yuriko MATSUBAYASHI
Keyword(s):  
Sediment Concentration ◽  
Laboratory Measurement ◽  
Light Extinction ◽  
High Sediment

Effect of Fine Sediments on the Performance of Axial Pumps

2008 ◽  
Author(s):  
Abdullah Saeed Al-Ghamdi
Keyword(s):  
Fine Sand ◽  
Sediment Concentration ◽  
Input Power ◽  
Fine Sediment ◽  
Motor Speed ◽  
Fine Sediments ◽  
Axial Pump ◽  
Axial Pumps ◽  
Work Done ◽  
Commercial Size

This study presents experimental work done to investigate the effect of fine sediment concentration on the performance of axial pumps. The pump was tested at three different motor speeds of 1000 rpm, 1150 rpm and 1350 rpm. At each motor speed, the pump was tested at three different sediment concentrations by weight of 0%, 2.485% and 8.10%. The sediment used in the investigation consists of a mixture of fine sand, silt and clay (16% fine sand, 38% silt and 46% clay). Results show that the efficiency of the axial pump is negatively influenced by the presence of fine sediments in the flow. As the sediment concentration increases to 8.10% the maximum reduction in axial pump’s efficiency for the range tested reached about 30% for motor speed of 1350 rpm and up to 40% for the lower motor speed of 1000 rpm. The reduction in the efficiency may be attributed to the change in the viscosity of the fluid that required higher torque (hence higher input power) to produce the same discharge. These results provide an evidence of a considerable reduction of axial pumps efficiency when used to pump water with fine sediment of silt and clay. However, further investigation is recommended for commercial size pumps and at different sediment concentrations and different composition of sediment.

scholarly journals Analysis on the Runoff and Sediment Yielding of “7.26” Rainstorm in 2017 in the Dali River Basin

2018 ◽  
Vol 53 ◽  
pp. 03025
Author(s):  
WenYong Gao ◽  
ShuangYan Jin ◽  
ShaoMeng Guo
Keyword(s):  
Ecological Restoration ◽  
River Basin ◽  
High Intensity ◽  
Soil Conservation ◽  
Sediment Concentration ◽  
Peak Discharge ◽  
Underlying Surface ◽  
The Relationship ◽  
High Sediment ◽  
Hydrological Regimes

Hydrological regimes of the “7.26” rainstorm and flood in 2017 in the Dali River basin are illustrated, the runoff and sediment of the flood is calculated. The relationship between peak discharge, runoff and sediment of history floods and the corresponding mean rainfall and combined rainfall factor are established respectively. It is found that the point of “7.26” flood locates at the upper left or in the middle of the history points group. The results show that after the implementation of water and soil conservation and ecological restoration policy for several decades, the underlying surface of the Dali River basin has changed to some degree, but encountered with the high intensity rainfall such as "7.26", it will still generate the flood of high sediment concentration.

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