scholarly journals Flow and bed topography in a meandering compound channel with phase difference between the alignment of the main channel and levee

1996 ◽  
Vol 40 ◽  
pp. 941-946
Author(s):  
Shoji FUKUOKA ◽  
Setsuo MIYAZAKI ◽  
Hiroya OHGUSHI ◽  
Daisuke KAMURA
Keyword(s):  
Phase Difference ◽  
Main Channel ◽  
Compound Channel ◽  
Bed Topography

scholarly journals Prediction of Boundary Shear Stress Distribution in Converging Compound Channel Using Gene Expression Programming

2022 ◽  
Author(s):  
Bandita Naik ◽  
Vijay Kaushik ◽  
Munendra Kumar
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Shear Force ◽  
Gene Expression Programming ◽  
Main Channel ◽  
Shear Stress Distribution ◽  
Force Distribution ◽  
Compound Channel ◽  
Boundary Shear ◽  
Boundary Shear Stress

Abstract The computation of the boundary shear stress distribution in an open channel flow is required for a variety of applications, including the flow resistance relationship and the construction of stable channels. The river breaches the main channel and spills across the floodplain during overbank flow conditions on both sides. Due to the momentum shift between the primary channel and adjacent floodplains, the flow structure in such compound channels becomes complicated. This has a profound impact on the shear stress distribution in the floodplain and main channel subsections. In addition, agriculture and development activities have occurred in floodplain parts of a river system. As a consequence, the geometry of the floodplain changes over the length of the flow, resulting in a converging compound channel. Traditional formulas, which rely heavily on empirical approaches, are ineffective in predicting shear force distribution with high precision. As a result, innovative and precise approaches are still in great demand. The boundary shear force carried by floodplains is estimated by gene expression programming (GEP) in this paper. In terms of non-dimensional geometric and flow variables, a novel equation is constructed to forecast boundary shear force distribution. The proposed GEP-based method is found to be best when compared to conventional methods. The findings indicate that the predicted percentage shear force carried by floodplains determined using GEP is in good agreement with the experimental data compared to the conventional formulas (R2 = 0.96 and RMSE = 3.395 for the training data and R2 = 0.95 and RMSE = 4.022 for the testing data).

Morphological effects of a hydraulic lifting dam on the middle Fenhe River, China

2021 ◽  
Author(s):  
Yufang Ni ◽  
Zhixian Cao ◽  
Wenjun Qi ◽  
Xiangbin Chai ◽  
Aili Zhao
Keyword(s):  
Shallow Water ◽  
General Pattern ◽  
Water Storage ◽  
Main Channel ◽  
Environmental Restoration ◽  
Two Dimensional ◽  
Compound Channel ◽  
Computationally Efficient ◽  
Bed Deformation ◽  
Numerical Predictions

<p>Hydraulic lifting dams become increasingly popular in China for water storage, river landscaping and environmental restoration. Inevitably, dams influence riverine morphology. Unfortunately, current understanding of this topic has remained rather limited. Here, the morphological effects of a hydraulic lifting dam on the middle Fenhe River, China are investigated. This reach features a compound channel and floodplains, and the riverbed is mainly composed of silt that can be easily eroded, indicating potential significant bed deformation. A computationally efficient depth-averaged two-dimensional shallow water hydro-sediment-morphodynamic model is employed. Unstructured meshes are refined around dam structures to accurately present topography. The numerical predictions show discrepancies of morphological responses of the main channel and floodplains to different operation schemes of the hydraulic lifting dam. This work helps to support decisions on the management of hydraulic lifting dams on the middle Fenhe River and reveals a general pattern for the morphological impact of hydraulic lifting dam.</p>

scholarly journals Simulations of Depth-Averaged Streamwise Velocity of Meandering Compound Channel using TELEMAC Modules

2018 ◽  
Vol 65 ◽  
pp. 07001
Author(s):  
Abdul Haslim Abdul Shukor Lim ◽  
Zulhilmi Ismai ◽  
Mohamad Hidayat Jama ◽  
Md. Ridzuan Makhtar
Keyword(s):  
Stokes Equations ◽  
Computing Time ◽  
Streamwise Velocity ◽  
Main Channel ◽  
Navier Stokes ◽  
Relative Depth ◽  
Compound Channel ◽  
Navier Stokes Equations ◽  
Numerical Tools ◽  
Good Agreement

Capabilities of numerical tools to simulate fluid problems significantly depend on its methods to solve for the Navier-Stokes equations. Different dimensional computing tools using the same horizontal meshes were used to simulate flow conditions inside non- and vegetation meandering compound channel. Both tools give good agreement for simulations of depth-averaged streamwise velocity inside the main channel, but its capabilities vary significantly for simulations on floodplains. Lower relative depth recorded a higher percentage of errors than flow with higher relative depth. Vegetation along the main channel increased the flows complexity especially in the area near the vegetation thus reducing the simulation capabilities of the computing tools. Simulations work by TELEMAC-3D significantly better in the areas with highly dimensional and turbulence conditions. TELEMAC-2D is still useful because of its simplicity and lower computing time and resources required.

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 FLOW AND BED TOPOGRAPHY IN A COMPOUND CHANNEL CONSISTING OF DIFFERENT PLAN SHAPES

2003 ◽  
Vol 47 ◽  
pp. 655-660 ◽  
Author(s):  
Shoji OKADA ◽  
Julio MASIS JIMENEZ ◽  
Shoji FUKUOKA ◽  
Hirotoshi Tamura ◽  
Ryo SHIGEMATSU
Keyword(s):  
Compound Channel ◽  
Bed Topography

scholarly journals Study on the Horizontal Distribution Law of Flood Water and Sediment Factors under the Effect of Vegetation on a Curved Beach

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1441
Author(s):  
Mingwu Zhang ◽  
Pan Li ◽  
Xiaoping Li ◽  
Aoxue Wang ◽  
Zhenhai Wang ◽  
...  
Keyword(s):  
Velocity Distribution ◽  
Model Test ◽  
Main Channel ◽  
Theoretical Research ◽  
Distribution Model ◽  
Main Stream ◽  
Compound Channel ◽  
Transverse Distribution ◽  
Water And Sediment ◽  
Beach Vegetation

The sediment-laden floodplain flood is affected by beach vegetation and the shape of curved compound channels. The laws of water and sediment exchange and deposition distribution in beach troughs are very complex and play a significant role in the formation and development of secondary suspended rivers, the adjustment of beach horizontal gradients, and even the evolution of flood control situations. This study used a combination of experimental simulations and theoretical research to carry out a generalized model test of floodplain flood evolution, analyzing the transverse distribution characteristics of sediment-laden flow and sediment factors in a curved compound channel under the conditions of beach vegetation, proposing a theoretical model of transverse distribution of velocity and sediment concentration that is based on the momentum equation considering the inertial force of the lateral secondary flow and river curvature. The results showed the following: (1) The model test results for floodplain flood in the compound channel with curved vegetation showed that the main stream was not only concentrated in the main channel but also appeared near the foot of the left and right bank levees and formed flood discharge along the embankment, as the beach siltation was mainly concentrated in the beach lip; (2) The arrangement of full vegetation on the beach had a uniform effect on the velocity distribution of the beach, which can reduce the phenomenon of excessive velocity at the foot of the beach and increase the velocity effect in the main channel; and (3) Through five numerical examples, the lateral velocity distribution model of a curved compound channel with beach vegetation was tested and, in general, the analysis model was consistent with the experimental results. The research results will provide a theoretical basis for river management and have great significance for enriching the basic theory of water and sediment movement and promoting the integration of hydraulics, river dynamics, and ecology.

scholarly journals Apparent roughness coefficient in overbank flows

2021 ◽  
Vol 3 (7) ◽  
Author(s):  
João N. Fernandes
Keyword(s):  
Shear Stress ◽  
Channel Flow ◽  
Isotropic Turbulence ◽  
Single Channel ◽  
Main Channel ◽  
Roughness Coefficient ◽  
Compound Channel ◽  
Secondary Currents ◽  
Flow Mechanisms ◽  
Overbank Flows

AbstractOverbank flows occur in alluvial valleys during flood events when the conveyance of main channel of rivers is exceeded. Once floodplains are inundated and the so-called compound channel flow is observed, the faster flow in the main channel interacts with the slower flow in the floodplain featuring a much more pronounced 3D flow structure compared to single channel flow. These flow mechanisms comprise a shear layer near the interface, lateral momentum transfer and strong secondary currents due to the non-isotropic turbulence. This paper starts by giving an overview of the main flow mechanisms in compound channels pointing out the importance of taking into account the apparent shear stress generated between the main channel and the floodplain flows due to the interaction of these flows. A new simple model was developed to include the apparent shear stress concept as a correction of the Manning roughness coefficient of main channel and floodplains. The proposed method for predicting stage–discharge relationships was calibrated and validated by experimental data from several compound channel facilities. A significant improvement in prediction of the compound channel conveyance in comparison with the traditional methods was achieved.

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