Transient bottom topography changes in alluvial streams

The development of a quasi two-dimensional computational model for simulating the transient variations of bed topography profiles in alluvial river channels is reported. The formulation of the model is based on combining the longitudinal flow momentum with the continuity principle of the sediment bed load. The Engelund-Hansen formula is employed in estimating the total sediment bed load along the reach of a river channel. The lateral bed load contribution from the total load is calculated in the same way as in calculating the lateral secondary currents from the main flow velocities. The numerical scheme and the computational procedure used in the study are described in detail. The simulated bed level profiles are verified through comparisons with experimental and field measurements taken from case studies in the literature for different flow conditions, channel characteristics, and sediment properties. The correlation between flow discharge, bed load, boundary friction, and channel slope is discussed. On the basis of the reasonably good comparisons with field data, it may be deduced that the model can be used for predicting the bottom topography variations in river channels.Key words: meandering rivers, bottom topography, sediment transport, bed load, boundary roughness, field measurements, experimental data, computational modelling, finite difference method.

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Simulation of the meander cut-off by 2D hydrodynamic model for erodible bed

10.5194/egusphere-egu21-6016 ◽

2021 ◽

Author(s):

Tatiana Fedorova ◽

Vitaly Belikov ◽

Andrei Alabyan

Keyword(s):

Bottom Topography ◽

Gravitational Effect ◽

High Water ◽

Computational Domain ◽

River Channels ◽

Time Step ◽

Channel Deformations ◽

Computational Mathematics ◽

Secondary Currents ◽

Meandering Channel

The retrospective simulation of the Pyoza river (Arkhangelsk region, Russia) meander cut-off in 2003-2008 has been undertaken. As a result of the river bend straightening two large villages were cut off from the road network of the region.The initial data for modeling were obtained by analyses of archive satellite images for the period from 1997 together with the runoff data, as well as by the field survey of September 2019. The simulation was performed by the latest version of the STREAM_2D CUDA software, using a new method for the numerical solution of two-dimensional Saint-Venant equations [1]. It was adapted for the complicated bottom topography typical for a wide floodplain with a meandering channel flooded in high water stage.The mass-exchange equations for three layers of sediment over the unerodible bed were solved together with the hydrodynamic equations. When calculating channel deformations, the gravitational effect due to bottom slope and the influence of secondary currents on the sediment shift were taken into account [2].The Pyoza river is the lowest large tributary of the Mezen&#8217; river flowing into the White sea. It is distinguished by a typical alluvial channel, meandering along wide floodplain composed by sands and sandy loams. The maximum runoff usually corresponds to spring snow-melting and can reach 1500-2000 m3/s.To schematize the computational domain of the Pyoza river section of 13 km long, a hybrid grid of irregular structure was constructed, consisting of 37 329 cells of a quadrangular shape for the channel and a triangular one for the floodplain.The simulation started at the year 1997 when where was no any rill across the meander neck. The time step of calculation was taken to be one day.Modeling made it possible to simulate realistically the essential steps and mechanisms of the meander cut-off: the development of a pioneer straightening rill, its widening and deepening, as well as blocking of the old channel by a point bar in its upper reaches, as well as its further silting and aggradation.1. Aleksyuk A.I., Belikov V.V. (2017): Simulation of shallow water flows with shoaling areas and bottom discontinuities. Computational Mathematics and Mathematical Physics, Volume 57, issue 2, pp. 318&#8211;339. https://doi.org/10.1134/S09655425170200262. Aleksyuk &#1040;. I., Belikov V. V., Borisova N. M., Fedorova T. A. (2018): Numerical modeling of non-uniform sediment transport in river channels. Water Resources, Volume 45, Special Issue S1, pp. 11&#8211;17. http://dx.doi.org/10.1134/S0097807818050275

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Sediment Transport and Water Flow Resistance in Alluvial River Channels: Modified Model of Transport of Non-Uniform Grain-Size Sediments

Water ◽

10.3390/w13152038 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2038

Author(s):

Gennady Gladkov ◽

Michał Habel ◽

Zygmunt Babiński ◽

Pakhom Belyakov

Keyword(s):

Sediment Transport ◽

Water Flow ◽

Transport Model ◽

Flow Characteristics ◽

Field Measurements ◽

Field Investigation ◽

Empirical Modeling ◽

River Channels ◽

Channel Deformations ◽

East European

The paper presents recommendations for using the results obtained in sediment transport simulation and modeling of channel deformations in rivers. This work relates to the issues of empirical modeling of the water flow characteristics in natural riverbeds with a movable bottom (alluvial channels) which are extremely complex. The study shows that in the simulation of sediment transport and calculation of channel deformations in the rivers, it is expedient to use the calculation dependences of Chézy’s coefficient for assessing the roughness of the bottom sediment mixture, or the dependences of the form based on the field investigation data. Three models are most commonly used and based on the original formulas of Meyer-Peter and Müller (1948), Einstein (1950) and van Rijn (1984). This work deals with assessing the hydraulic resistance of the channel and improving the river sediment transport model in a simulation of riverbed transformation on the basis of previous research to verify it based on 296 field measurements on the Central-East European lowland rivers. The performed test calculations show that the modified van Rijn formula gives the best results from all the considered variants.

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Organic near-bed fluid and particulate transport in combined sewers

Water Science & Technology ◽

10.2166/wst.1995.0201 ◽

1995 ◽

Vol 31 (7) ◽

pp. 61-68 ◽

Cited By ~ 3

Author(s):

E. Ristenpart ◽

R. M. Ashley ◽

M. Uhl

Keyword(s):

Bed Load ◽

Erosion And Deposition ◽

Sediment Bed ◽

Solids Transport ◽

Particulate Transport ◽

Sediment Deposits ◽

Dense Fluid ◽

Deposition Processes ◽

Continuous Field ◽

Heterogeneity Of Solids

Studies in Germany, Belgium, France and Scotland have revealed that there are significant solids transport gradients in the depth of foul and combined sewage flows. Continuous field observations of changes in depths of sediment deposits in combined sewers have also indicated that there is an interaction between the erosion and deposition processes and changes in the mass transport of solids in regions in the overlying flow. A fuller understanding of the interactive phenomena is essential for both sewer sediment management and the minimization of associated pollution from wash-out of solids via CSOs. The paper presents results from the detailed studies in Hildesheim, Germany and those carried out in Dundee, Scotland, investigating the heterogeneity of solids movement with regard to gross solids, erosion of sewer sediments and their interactions with the suspended transport phases and the layer of very dense fluid found to be transported under certain circumstances, near the sediment bed or sewer invert (traditionally called ‘bed-load’).

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Modeling Tidal Stress, Circulation, and Mixing in the Bristol Channel as a Prerequisite for Ecosystem Studies

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f83-265 ◽

1983 ◽

Vol 40 (S1) ◽

pp. s8-s19 ◽

Cited By ~ 19

Author(s):

R. J. Uncles

Keyword(s):

Numerical Model ◽

Ecosystem Model ◽

Hydrodynamical Model ◽

Bed Load ◽

Sediment Bed ◽

Tidal Stress ◽

Horizontal Mixing ◽

Ecosystem Studies ◽

Residual Flows ◽

Model Agreement

A depth-averaged hydrodynamical numerical model is used to evaluate tidal stresses, currents, and mixing in the Bristol Channel and Severn Estuary. Benthic macrofaunal associations and sediment bed types are shown to depend on the magnitude of the tidal stress, and the direction of sediment transport (as bed-load) in the central parts of the Channel is shown to be a consequence of ebb dominated stress. This asymmetry in the tidal stress is mainly caused by M4 currents, and computed M4 elevations and currents are compared with observed values at a number of stations. Residual flows and horizontal mixing are deduced from the hydrodynamical model, and used to construct transport relationships for an ecosystem model. Agreement between observed salinity over a number of years and that computed by the ecosystem model is generally good.Key words: Bristol Channel, hydrodynamical model, salinity model, tidal stress, M4 tides, sediment movement

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High-frequency field measurements and time-dependent computational modelling for wind turbine siting

Journal of Wind Engineering and Industrial Aerodynamics ◽

10.1016/j.jweia.2010.12.006 ◽

2011 ◽

Vol 99 (2-3) ◽

pp. 123-129 ◽

Cited By ~ 8

Author(s):

C. Abiven ◽

J.M.L.M. Palma ◽

O. Brady

Keyword(s):

Wind Turbine ◽

High Frequency ◽

Computational Modelling ◽

Field Measurements ◽

Time Dependent ◽

High Frequency Field ◽

Frequency Field

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Field Measurements of Secondary Currents in Straight Rivers

Journal of Hydraulic Engineering ◽

10.1061/(asce)0733-9429(1993)119:5(598) ◽

1993 ◽

Vol 119 (5) ◽

pp. 598-614 ◽

Cited By ~ 62

Author(s):

Iehisa Nezu ◽

Akihiro Tominaga ◽

Hiroji Nakagawa

Keyword(s):

Field Measurements ◽

Secondary Currents

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Sediment Bed-Load Transport: A Standardized Notation

Geosciences ◽

10.3390/geosciences10090368 ◽

2020 ◽

Vol 10 (9) ◽

pp. 368

Author(s):

Ulrich Zanke ◽

Aron Roland

Keyword(s):

Shear Stress ◽

Critical Shear Stress ◽

Basic Structure ◽

Structural Formula ◽

Bed Load ◽

Viscous Effects ◽

Data Set ◽

Sediment Bed ◽

Load Transport ◽

Bed Load Transport

Morphodynamic processes on Earth are a result of sediment displacements by the flow of water or the action of wind. An essential part of sediment transport takes place with permanent or intermittent contact with the bed. In the past, numerous approaches for bed-load transport rates have been developed, based on various fundamental ideas. For the user, the question arises which transport function to choose and why just that one. Different transport approaches can be compared based on measured transport rates. However, this method has the disadvantage that any measured data contains inaccuracies that correlate in different ways with the transport functions under comparison. Unequal conditions also exist if the factors of transport functions under test are fitted to parts of the test data set during the development of the function, but others are not. Therefore, a structural formula comparison is made by transferring altogether 13 transport functions into a standardized notation. Although these formulas were developed from different perspectives and with different approaches, it is shown that these approaches lead to essentially the same basic formula for the main variables. These are shear stress and critical shear stress. However, despite the basic structure of these 13 formulas being the same, their coefficients vary significantly. The reason for that variation and the possible effect on the bandwidth of results is identified and discussed. A further result is the finding that not only shear stress affects bed-load transport rates as is expressed by many transport formulas. Transport rates are also significantly affected by the internal friction of the moving sediment as well as by the friction fluid-bed. In the case of not fully rough flow conditions, also viscous effects and thus the Reynolds number becomes of importance.

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