Direct numerical simulations of spanwise slope-induced turbidity currents in a fine sediment-laden steady turbulent channel: Role of suspended sediment concentration and settling velocity

2018 ◽  
Vol 30 (12) ◽  
pp. 126601 ◽  
Author(s):  
Celalettin Emre Ozdemir ◽  
Xiao Yu
Keyword(s):  
Numerical Simulations ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Settling Velocity ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Direct Numerical Simulations ◽  
Turbidity Currents

scholarly journals Fine Sediment Modeling During Storm-Based Events in the River Bandon, Ireland

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1523 ◽  
Author(s):  
Juan T. García ◽  
Joseph R. Harrington
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Storm Event ◽  
Storm Events ◽  
Event Scale ◽  
Model Based ◽  
Sediment Volume ◽  
Bed Erosion

The River Bandon located in County Cork (Ireland) has been time-continuously monitored by turbidity probes, as well as automatic and manual suspended sediment sampling. The current work evaluates three different models used to estimate the fine sediment concentration during storm-based events over a period of one year. The modeled suspended sediment concentration is compared with that measured at an event scale. Uncertainty indices are calculated and compared with those presented in the bibliography. An empirically-based model was used as a reference, as this model has been previously applied to evaluate sediment behavior over the same time period in the River Bandon. Three other models have been applied to the gathered data. First is an empirically-based storm events model, based on an exponential function for calculation of the sediment output from the bed. A statistically-based approach first developed for sewers was also evaluated. The third model evaluated was a shear stress erosion-based model based on one parameter. The importance of considering the fine sediment volume stored in the bed and its consolidation to predict the suspended sediment concentration during storm events is clearly evident. Taking into account dry weather periods and the bed erosion in previous events, knowledge on the eroded volume for each storm event is necessary to adjust the parameters for each model.

scholarly journals Time Evolution of Estuarine Turbidity Maxima in Well-Mixed, Tidally Dominated Estuaries: The Role of Availability- and Erosion-Limited Conditions

2018 ◽  
Vol 48 (8) ◽  
pp. 1629-1650 ◽  
Author(s):  
Ronald L. Brouwer ◽  
George P. Schramkowski ◽  
Yoeri M. Dijkstra ◽  
Henk M. Schuttelaars
Keyword(s):  
River Discharge ◽  
Suspended Sediment Concentration ◽  
Time Lag ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Time Varying ◽  
Hydrodynamic Conditions ◽  
Good Qualitative Agreement ◽  
Estuarine Turbidity Maxima

AbstractUsing an idealized width-averaged process-based model, the role of a mud pool on the bed and time-varying river discharge on the trapping of fine sediment is systematically investigated. For this purpose, a dynamically and physically motivated description of erodibility is presented, which relates the amount of sediment on the bed to the suspended sediment concentration (SSC). We can distinguish between two states: in the availability-limited state, the SSC is limited by the amount of erodible sediment at the bed. Over time, under constant forcing conditions, the estuary evolves to morphodynamic equilibrium. In the erosion-limited state, there is an abundant amount of sediment at the bed so that sediment pickup occurs at the maximum possible rate. The SSC is then limited by the local hydrodynamic conditions. In this state, the estuary keeps importing sediment, forming an erodible bottom pool that grows in time. These two states can be used to explain the response of an estuary to changing river discharge. Under availability-limited conditions, periods of high river discharge push estuarine turbidity maxima (ETMs) downstream, while drier periods allow ETMs to move upstream. However, when the estuary is in an erosion-limited state during low river discharge, a bottom pool is formed. When the discharge then increases, it takes time to deplete this pool, so that an ETM located over a bottom pool moves with a significant time lag relative to changes in the river discharge. Good qualitative agreement is found between model results and observations in the Scheldt Estuary of surface SSC using a representative year of discharge conditions.

scholarly journals How Sediment Transport Sways Wetland Stability

Eos ◽  
2016 ◽  
Vol 97 ◽  
Author(s):  
Lily Strelich
Keyword(s):  
Sediment Transport ◽  
Sea Level Rise ◽  
Suspended Sediment ◽  
Sea Level ◽  
Coastal Wetlands ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration

Scientists examine the role of variables like tides and suspended sediment concentration to improve methods of evaluating coastal wetlands and how they may respond to future sea level rise.

Determination of Settling Velocity of Suspended Sediment in Estuary

2014 ◽  
Vol 670-671 ◽  
pp. 805-808 ◽  
Author(s):  
Hui Ming Huang ◽  
Da Ke Chen ◽  
Wei Na Zhang ◽  
Cheng Chen
Keyword(s):  
Suspended Sediment ◽  
Settling Velocity ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Cohesive Sediments ◽  
The Changjiang River ◽  
Sediment Particle Size ◽  
Logarithmic Distribution ◽  
Sediment Data

The settling velocity of sediment is a hot issue and a basic problem in study of sediment transport and estuarine engineering. According to field hydrodynamics and sediment data around the South Passage of the Changjiang River in China, this paper detected the characteristics of sediment particle size and vertical distribution pattern of suspended sediment concentration, and further estimated the settling velocity of suspended sediment in three methods. The results show that the sediments including suspended and bed load can be categorized into cohesive sediments and the sediment concentration profile agree well with logarithmic distribution. Furthermore, by comparison, it is found that the Rouse formula is more reasonable for estimating the settling velocity of fine sediment, but the Zhang Ruijin and Stokes formula obviously underestimate the values of settling velocity, caused by do not taking into account the flocculation of fine sediment in estuary.

scholarly journals Effect of self-stratification on sediment diffusivity in channel flows and boundary-layers: a study using Direct Numerical Simulations

2013 ◽  
Vol 1 (1) ◽  
pp. 923-950
Author(s):  
S. Dutta ◽  
M. I. Cantero ◽  
M. H. Garcia
Keyword(s):  
Particle Size ◽  
Numerical Simulations ◽  
Suspended Sediment ◽  
Channel Flow ◽  
Sediment Concentration ◽  
Suspended Load ◽  
Direct Numerical Simulations ◽  
Channel Flows ◽  
Concentration Data ◽  
Effect Of Particle Size

Abstract. Sediment transport in nature comprises of bed-load and suspended load, and precise modelling of suspended load transport is essential for accurate sediment flux estimation. Traditionally, non-cohesive suspended sediment has been modelled using the advection-diffusion equation (Garcia, 2008), where the success of the model is largely dependent on accurate approximation of the sediment diffusion coefficients. The current study explores the effect of self-stratification on sediment diffusivity using suspended sediment concentration data from Direct Numerical Simulations (DNS) of flows subjected to different levels of stratification, where the level of stratification is dependent on the particle size (parameterized using particle fall velocity V~) and volume-averaged sediment concentration (parameterized using shear Richardson number Riτ). Two distinct configurations were explored, first the channel flow configuration (similar to flow in a pipe or a duct) and second, a boundary layer configuration (similar to open-channel flow). Self-stratification was found to modulate the turbulence intensity (Cantero et al., 2009), which in turn was found to reduce vertical sediment diffusivity in portions of the domain exposed to turbulence damping. Effect of particle size on vertical sediment diffusivity has been studied in the past by several authors (Rouse, 1937; Coleman, 1970; Nielsen and Teakle, 2004); so in addition to the effect of particle size, the current study also explores the effect of sediment concentration on vertical sediment diffusivity. The results from the DNS simulations were compared with experiments (Ismail, 1952; Coleman, 1986) and field measurements (Coleman, 1970); and were found to agree qualitatively especially for the case of channel flows. The aim of the study was to understand the effect of stratification due to suspended sediment on vertical sediment diffusivity for different flow configurations, in order to gain insight of the underlying physics, which will eventually help us to improve the existing models for sediment diffusivity.

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