scholarly journals Experiments on Longitudinal and Transverse Bedload Transport in Sine-Generated Meandering Channels

2021 ◽  
Vol 11 (14) ◽  
pp. 6560
Author(s):  
Li He ◽  
Dong Chen ◽  
Donatella Termini ◽  
Shiyan Zhang ◽  
Zhenhui Zhu
Keyword(s):  
Longitudinal Direction ◽  
Bedload Transport ◽  
Bed Topography ◽  
Bed Deformation ◽  
Meandering Channels ◽  
Curved Channels ◽  
Initial Location ◽  
Moving Direction ◽  
Point Bars ◽  
Gain Loss

Bedload grains in consecutive meandering bends either move longitudinally or across the channel centerline. This study traces and quantifies the grains’ movement in two laboratorial sine-generated channels, i.e., one with deflection angle θ0 = 30° and the other 110°. The grains originally paved along the channels are uniform in size with D = 1 mm and are dyed in various colors, according to their initial location. The experiments recorded the changes in the flow patterns, bed deformation, and the gain-loss distribution of the colored grains in the pool-bar complexes. We observed the formation of two types of erosion zones during the process of the bed deformation, i.e., Zone 1 in the foreside of the point bars and Zone 2 near the concave bank downstream of the bend apexes. Most grains eroded from Zone 1 are observed moving longitudinally as opposed to crossing the channel centerline. Contrastingly, the dominant moving direction of the grains eroded from Zone 2 changes from the longitudinal direction to the transversal one as the bed topography evolves. Besides, most building material of the point bars comes from the upstream bends, although low- and highly curved channels behave differently.

scholarly journals Topics in fluvial and lagoon morphodynamics

2002 ◽  
Author(s):  
Luca Solari
Keyword(s):  
Flow Field ◽  
Bedload Transport ◽  
Observational Evidence ◽  
Field Pattern ◽  
Tidal Channels ◽  
New Model ◽  
Bed Topography ◽  
Meandering Channels ◽  
Present Book ◽  
Transverse Slope

The present book covers topics both on fluvial and lagoon morphodynamics. The first part is dedicated to tidal environments. Topics include an overview of main morphological features and mechanisms of estuaries and tidal channels and a model devoted to investigate flow field pattern and bed topography in tidal meandering channels and a comparison with recent observational evidence of meanders within different tidal environments. The general failure of Bagnold hypothesis when applied to equilibrium bedload transport at even relatively modest transverse slope is demonstrated. A new model is then proposed based on an empirical entrainment formulation of bed grains.

Flow Patterns and Bed Deformation in a Meandering Channel with Different Flow Conditions

2013 ◽  
Vol 405-408 ◽  
pp. 2292-2296
Author(s):  
Dong Dong Jia ◽  
Peng Fei Hei ◽  
Xue Jun Shao ◽  
Xi Bao Zhang
Keyword(s):  
Velocity Distribution ◽  
Transport Model ◽  
Maximum Velocity ◽  
Flow Conditions ◽  
Meandering Channel ◽  
Bed Deformation ◽  
Meandering Channels ◽  
Small Flow ◽  
Flow And Sediment Transport ◽  
Deformation Patterns

The velocity distribution and bed deformation patterns in a meandering channel with consecutive bends were investigated by using both an experimental study and a 3-D flow and sediment transport model. The simulated results from the 3-D model agree well with the experimental data. The flow structure and bed deformation patterns in channel bends with different flow conditions were analyzed. Modeled results demonstrated that the velocity distribution and bed deformation in the meandering channel depend mostly on the flow regimes. For the case of small flow discharge, the maximum velocity occurs in the vicinity of concave bank. For the case of large discharge, the maximum velocity occurs near the center part of the channel. Consequently, bed deformation patterns in meandering channels will be influenced by the flow conditions.

Spatial Distribution of Thin Interbeds in Point Bars of Meadering Channels: Case Study of Block X in Daqing Oilfield

2012 ◽  
Vol 524-527 ◽  
pp. 199-204
Author(s):  
Bai Quan Yan ◽  
Xiao Lei Tian ◽  
Hong Qing Kang ◽  
Long Wang
Keyword(s):  
Oil And Gas ◽  
Outer Boundary ◽  
Structural Features ◽  
Gas Reservoirs ◽  
Oil Accumulation ◽  
Meandering Channels ◽  
Oil Distribution ◽  
Remaining Oil ◽  
Point Bars ◽  
Abandoned Channels

Reservoirs in point bars of meandering channels account for a high proportion in oil and gas reservoirs, with much impact of complicated architecture on remaining oil accumulation and distribution. Thus study on inner architecture of point bars and its impact on remaining oil distribution are important. This paper selects Unit III in Block A in Daqing Oilfield with data in filled well patterns and cores to study inner architecture of subsurface single sand bodies, and analyzes 3D structural features of meandering point bars in Xingbei deltaic plain in Daqing Placanticline. Architecture parameters of lateral accretion shale interbeds are: eastward dip averagely 7°, the upper, middle and lower dip in same accretion face are respectively 10°, 7° and 3°, the width is 15-42m. They are vertically imbricated series and areally corner points of abandoned channels on both sides of meandering rings as track collection intersections, and progressive and curvature reducing arc sets with abandoned channels of meandering rings as outer boundary. This pattern provides geologic basis for successive study on remaining oil.

scholarly journals Distribution of primary and secondary currents in sine-generated bends

Water SA ◽  
2018 ◽  
Vol 44 (1 January) ◽  
Author(s):  
Li He
Keyword(s):  
Secondary Flow ◽  
Flow Analysis ◽  
Primary Flow ◽  
Secondary Currents ◽  
Meandering Channel ◽  
Meandering Channels ◽  
Curved Channels ◽  
Mobile Bed ◽  
Using Data ◽  
Curvature Driven

The secondary circulation in a meandering channel redistributes the velocity over the bend. However, the shift of primary flow by secondary currents is not quantitatively understood, due to the difficulty in isolating the role of curvature-driven secondary flow from that of topography-driven secondary flow in bed-deformed meanders. The influences of curvature-driven and topography-driven secondary currents on the redistribution of primary flow in sine-generated meandering channels were examined by CCHE2D. The model is calibrated using data measured in two sets of laboratory experiments including flat-bed flow and mobile-bed flow. Analysis indicated that topography-induced current mainly contributes to the redistribution of primary flow from inner to outer bank in the curved channels, rather than the secondary flow driven by curvature.

scholarly journals Bed-Shear Velocity Measurement in Curved Open Channel

2021 ◽  
Vol 004 (01) ◽  
pp. 093-105
Author(s):  
Sumiadi Sumiadi ◽  
Bambang Kironoto ◽  
Djoko Legono ◽  
Istiarto Istiarto
Keyword(s):  
Stress Distribution ◽  
Reynolds Stress ◽  
Measurement Data ◽  
Shear Velocity ◽  
Complex Flow ◽  
Curved Channel ◽  
Distribution Method ◽  
Bed Topography ◽  
Curved Channels ◽  
River Bed

Generally, the condition of the rivers in Indonesia are alluvial rivers which had meanders, where the change in the river bed topography often occur. One of the parameters associated with changes in the river bed topography is bed-shear velocity, or Reynolds stress. The bed-shear velocity can be calculated by the Reynolds stress distribution method and the Clauser method which commonly used in straight channels. In fact, on natural channel there is a curve and even a meandering channel. With more complex flow conditions, the use of the Clauser method in curved channels can be questioned, is it still accurate or not. In this paper, both methods will be discussed by comparing the measurement data in the laboratory using 180 curved channel with flat bed. The results of data analysis show that the use of these two methods in curved channels produces an average difference of around 19.81%, where the Clauser method gives greater results and better tendencies. Apart from the differences in the results given, it can be said that the Clauser method as well as the Reynolds stress distribution method can still be used to calculate the bed-shear velocity in the curved channel

scholarly journals Bar dynamics and sediment transport pulses in gravel-bed channels

2018 ◽  
Vol 40 ◽  
pp. 05047
Author(s):  
Blaise Dhont ◽  
Christophe Ancey ◽  
Patricio Bohorquez
Keyword(s):  
Sediment Transport ◽  
Laser Sheet ◽  
Water Discharge ◽  
Bedload Transport ◽  
Transport Rate ◽  
Experimental Conditions ◽  
Gravel Bed ◽  
Bed Topography ◽  
Sediment Transport Rate ◽  
Alternate Bars

Mountain rivers exhibit sediment transport rate fluctuations that often cover more than two orders of magnitude. Bedform migration is often cited as the key process that causes giant fluctuations in the sediment transport rate. To quantify the effect of bedform migration on transport rate, we ran laboratory experiments in a 19-m long 60-cm wide flume with well-sorted gravel bed. At the flume inlet, the water discharge and the particle flux were kept constant. Experiments were conducted over long times (typically > 500 h). Sediment transport rate was monitored at the flume outlet using accelerometers. Bed topography was scanned at high spatial resolution using a laser sheet. Water depth was measured using ultrasonic probes mounted on an automated rolling carriage. We observed that, under steady state experimental conditions, bed morphology played a key part in the generation of bedload transport fluctuations. The bars migrated downstream intermittently, producing the most important pulses. When the bar position was stable for a few hours, additional pulses resulted from sediment transfer from pool to pool, in the form of sediment waves (bedload sheets). Thus, in our experiments, alternate bars formed a two-entity system (bar + pool) with two distinctive functions: the bars contributed to fix and stabilize the bed whereas the pools were the preferential zones of short-term storage and transfer of sediment.

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