scholarly journals A coupled 1-D/2-D model for simulating river sediment transport and bed evolution

2020 ◽  
Vol 22 (5) ◽  
pp. 1122-1137
Author(s):  
Mezbache Salheddine ◽  
Paquier André ◽  
Hasbaia Mahmoud
Keyword(s):  
Sediment Transport ◽  
Flow Direction ◽  
Coupled Model ◽  
Computational Time ◽  
Bed Topography ◽  
Sedimentary Model ◽  
Lateral Coupling ◽  
Morphological Processes ◽  
Bed Evolution ◽  
D Model

Abstract The paper details the method to couple a 1-D hydro-sedimentary model to a 2-D hydro-sedimentary model in order to represent the hydrodynamics and morphological processes during a flood event along a river. Tested on two field cases, the coupled model is stable even in the case of generalized overflow over the riverbanks or of levee breaching. For lateral coupling, the coupled model allows saving computational time compared to a full 2-D model and to provide valuable results concerning the flooding features as well as the evolution of the bed topography. However, despite a similar simplified representation of the sediment features in the 1-D and 2-D models, some discrepancies appear in the case of upstream/downstream coupling along a cross section perpendicular to the flow direction because the assumption of homogeneous velocity and concentration is not valid for estimating sediment transport. Further research is necessary to be able to define a suitable distribution of the sediments on the 1-D side of the boundary between the two models.

scholarly journals Lower-stage plane bed topography is an outcome of rarefied, intermittent sediment transport

2021 ◽  
Author(s):  
Thomas Christopher Ashley ◽  
Suleyman Naqshband ◽  
Brandon McElroy
Keyword(s):  
Sediment Transport ◽  
Bed Topography ◽  
Lower Stage

Changes in Sediment Transport and Bed Topography in Response to Step-Up Flows in Laboratory Flume

2021 ◽  
Vol 147 (4) ◽  
pp. 06021002
Author(s):  
Daniel G. Wren ◽  
Eddy J. Langendoen ◽  
Roger A. Kuhnle
Keyword(s):  
Sediment Transport ◽  
Bed Topography ◽  
Laboratory Flume

scholarly journals Coupling Methodology for Studying the Far Field Effects of Wave Energy Converter Arrays over a Varying Bathymetry

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2899 ◽  
Author(s):  
Gael Verao Fernandez ◽  
Philip Balitsky ◽  
Vasiliki Stratigaki ◽  
Peter Troch
Keyword(s):  
Numerical Simulations ◽  
Wave Energy ◽  
Near Field ◽  
Coupled Model ◽  
Propagation Model ◽  
Irregular Waves ◽  
Computational Time ◽  
Far Field ◽  
Field Effects ◽  
Numerical Tool

For renewable wave energy to operate at grid scale, large arrays of Wave Energy Converters (WECs) need to be deployed in the ocean. Due to the hydrodynamic interactions between the individual WECs of an array, the overall power absorption and surrounding wave field will be affected, both close to the WECs (near field effects) and at large distances from their location (far field effects). Therefore, it is essential to model both the near field and far field effects of WEC arrays. It is difficult, however, to model both effects using a single numerical model that offers the desired accuracy at a reasonable computational time. The objective of this paper is to present a generic coupling methodology that will allow to model both effects accurately. The presented coupling methodology is exemplified using the mild slope wave propagation model MILDwave and the Boundary Elements Methods (BEM) solver NEMOH. NEMOH is used to model the near field effects while MILDwave is used to model the WEC array far field effects. The information between the two models is transferred using a one-way coupling. The results of the NEMOH-MILDwave coupled model are compared to the results from using only NEMOH for various test cases in uniform water depth. Additionally, the NEMOH-MILDwave coupled model is validated against available experimental wave data for a 9-WEC array. The coupling methodology proves to be a reliable numerical tool as the results demonstrate a difference between the numerical simulations results smaller than 5% and between the numerical simulations results and the experimental data ranging from 3% to 11%. The simulations are subsequently extended for a varying bathymetry, which will affect the far field effects. As a result, our coupled model proves to be a suitable numerical tool for simulating far field effects of WEC arrays for regular and irregular waves over a varying bathymetry.

scholarly journals Experimental Study of Submerged Vanes in Intakes under Sediment Feeding Conditions

2018 ◽  
Vol 40 ◽  
pp. 03016
Author(s):  
Aslı Bor Türkben
Keyword(s):  
Water Intake ◽  
River Flow ◽  
Flow Direction ◽  
Main Channel ◽  
Bed Topography ◽  
Before And After ◽  
Submerged Vane ◽  
Solid Discharge ◽  
Submerged Vanes ◽  
Intake Structure

Sediment is transported along the river flow and deposited in the mouth of the intake structure over time and reducing the water intake capacity. Nowadays, many water intake structures lose their function and are closed to operation. To deal with this problem, recently, submerged vane application has offered a practical and economical solution. The aim of this study was to evaluate the efficiency of three vane installations under sediment feeding conditions by comparing the bed topography before and after vanes were installed. For that purpose, experiments were carried out in a laboratory channel running for 90-degree intake angle. Three vanes were installed in one column at near the intake entrance. The vanes dimensions were equal to; 3cm height, 12cm long, 10 mm thick, and aligned with α = 20° angle to flow direction. The tests were run until equilibrium was reached, i.e. when the outgoing solid discharge was equal or larger than 90% of the incoming. Once the bed topography remained stable, bed and water level surfaces were measured. tests were carried out by feeding sediment from upstream of the main channel.

scholarly journals Numerical Simulation of Morphological Changes due to the 2004 Tsunami Wave around Banda Aceh, Indonesia

Geosciences ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 125 ◽  
Author(s):  
Teuku Rasyif ◽  
Shigeru Kato ◽  
Syamsidik ◽  
Takumi Okabe
Keyword(s):  
Sediment Transport ◽  
Morphological Changes ◽  
Coupled Model ◽  
Indian Ocean Tsunami ◽  
Hydrodynamic Process ◽  
Tsunami Waves ◽  
The North ◽  
Tsunami Model ◽  
2004 Tsunami ◽  
Banda Aceh

The 2004 Indian Ocean tsunami caused massive morphological changes around the coast of Sumatra, Indonesia. This research investigates the coastal morphological changes in the Banda Aceh area via coupling a hydrodynamic model with a sediment transport module. The Cornell Multigrid Coupled Tsunami Model (COMCOT) was coupled with the XBeach Model to simultaneously simulate sediment transport and the hydrodynamic process during the tsunami. The coupled model is known as COMCOT-SED. Field bathymetric data measured in 2006 were used to validate the coupled model. This study reveals that the tsunami’s impact was more severe on the eastern part of the coast, where it hit directly. Meanwhile, the western part of the coast suffered a lower impact because of the sheltering effects from a series of small islands and a headland to the north. This study has shown that the model results from COMCOT-SED are consistent with field data and show where the tsunami waves caused offshore erosion.

scholarly journals Comparison of Local and Global Optimization Methods for Calibration of a 3D Morphodynamic Model of a Curved Channel

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1333
Author(s):  
Vahid Shoarinezhad ◽  
Silke Wieprecht ◽  
Stefan Haun
Keyword(s):  
Global Optimization ◽  
Sediment Transport ◽  
Numerical Model ◽  
Numerical Models ◽  
Optimization Algorithms ◽  
Flow Characteristics ◽  
Optimization Methods ◽  
Computational Time ◽  
Curved Channel ◽  
Time Model

In curved channels, the flow characteristics, sediment transport mechanisms, and bed evolution are more complex than in straight channels, owing to the interaction between the centrifugal force and the pressure gradient, which results in the formation of secondary currents. Therefore, using an appropriate numerical model that considers this fully three-dimensional effect, and subsequently, the model calibration are substantial tasks for achieving reliable simulation results. The calibration of numerical models as a subjective approach can become challenging and highly time-consuming, especially for inexperienced modelers, due to dealing with a large number of input parameters with respect to hydraulics and sediment transport. Using optimization methods can notably facilitate and expedite the calibration procedure by reducing the user intervention, which results in a more objective selection of parameters. This study focuses on the application of four different optimization algorithms for calibration of a 3D morphodynamic numerical model of a curved channel. The performance of a local gradient-based method is compared with three global optimization algorithms in terms of accuracy and computational time (model runs). The outputs of the optimization methods demonstrate similar sets of calibrated parameters and almost the same degree of accuracy according to the achieved minimum of the objective function. Accordingly, the most efficient method concerning the number of model runs (i.e., local optimization method) is selected for further investigation by setting up additional numerical models using different sediment transport formulae and various discharge rates. The comparisons of bed topography changes in several longitudinal and cross-sections between the measured data and the results of the calibrated numerical models are presented. The outcomes show an acceptable degree of accuracy for the automatically calibrated models.

Research on Jiepai Riverbed Evolution Law and its Evolution Trend Forecast in Middle Yangtze River

2014 ◽  
Vol 926-930 ◽  
pp. 4292-4297
Author(s):  
Cheng Tao Huang
Keyword(s):  
Sediment Transport ◽  
Yangtze River ◽  
Mathematic Model ◽  
Beach Erosion ◽  
Main Stream ◽  
Reservoir Impoundment ◽  
Close Relationship ◽  
Bed Evolution ◽  
The Right ◽  
Evolution Trend

After Three Gorges reservoir impoundment, sediment transport and bed evolution characteristic had changed in the lower Yangtze River. Based on the observational data, sediment transport and bed evolution characteristic of Jiepai reach had been analyzed. The results showed that Jiepai reach evolution had a close relationship with income flow and sediment conditions. In recent years, the income flow and sediment conditions were propitious to the development of left slot of heart beach. It also had accelerated the low beach erosion in transition section and siltation in Xindijia. A 2-D mathematic model and river physical model had been used to forecast the river evolution trend. The results showed that the staggered beach would still not stay steady with the reservoir impoundment. The periodic time of evolution could become longer. Xiru bank beach in right bank of upper Jiepai reach would deposit and move downwards. The main stream discharge would centralize and increase. The left channel of heart reach would be eroded and the right one would dwindle gradually by the squeezing of the heart reach. The right branch channel, as the main navigation channel, would deposit and become shallow. The transition reach would move downwards at outlet of left channel. The riffle would present a staggered shape and left branch channel would dwindle gradually. The waterway transportation condition would get worse.

scholarly journals An experimental study on sediment transport and bed evolution under different swash zone morphological conditions

2012 ◽  
Vol 68 ◽  
pp. 31-43 ◽  
Author(s):  
José M. Alsina ◽  
Iván Cáceres ◽  
Maurizio Brocchini ◽  
Tom E. Baldock
Keyword(s):  
Experimental Study ◽  
Sediment Transport ◽  
Swash Zone ◽  
Bed Evolution

Time dependent backward piping erosion 2D modeling with laminar flow transport equations

2020 ◽  
Author(s):  
Juan Pablo Aguilar-Lopez ◽  
Manuel Wewer ◽  
Thom Bogaard ◽  
Matthijs Kok
Keyword(s):  
Sediment Transport ◽  
Coupled Model ◽  
Mass Conservation ◽  
Element Model ◽  
Great Accuracy ◽  
Conservation Equation ◽  
Empirical Formulas ◽  
Important Conclusion ◽  
Scale Experiment ◽  
Piping Erosion

<p>Backward piping erosion (BEP) is a highly complex erosive process which occurs on granular soils when large head differences are exerted. This process represents a significant threat to dams and levees stability and therefore a large part of the design and reliability assessment of these water retaining structures is devoted to this single process. Several authors have achieved great accuracy in predicting the critical head difference that triggers the process but not so much has been studied regarding the time of occurrence and the duration of the erosive process.  In the present study we propose a 2D finite element model for which not only the critical head difference can be predicted but also the development of the erosive process in time. This was achieved by coupling the 2D Darcy partial differential equation with Exner’s 1D sediment transport mass conservation equation. Different laminar sediment transport rate empirical models were tested and used as inputs in the coupled model. To test the performance of the proposed model, the IJkdijk real scale experiment for piping erosion was simulated. The results show that the model is capable of predicting not only the critical head and its progression in time but also specific events of the process such as the instants of start of the erosion and the  complete seepage length development . An important conclusion of the study is that from several transport empirical formulas tested, the model from Yalin which is widely recognized by the sediment transport community performs the best.</p>

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