scholarly journals Numerical Simulation of the Influence of Spur Dikes Spacing on Local Scour and Flow

2019 ◽  
Vol 9 (11) ◽  
pp. 2306
Author(s):  
Jian Ning ◽  
Guodong Li ◽  
Shanshan Li
Keyword(s):  
Shear Stress ◽  
Pearson Correlation ◽  
Fixed Bed ◽  
Maximum Velocity ◽  
Turbulent Energy ◽  
Local Scour ◽  
Shielding Effect ◽  
Scour Depth ◽  
Spur Dike ◽  
Spur Dikes

The spacing of spur dikes is an important consideration for the layout of spur dike channels. This study focuses on the local scour morphology and flow field characteristics of spur dikes with different spacings. The results show that the maximum scour depth is generally found in the vicinity of the first spur dike head. With the increase of the spacing of spur dikes, the shielding effect of the first spur dike is weakened. The maximum velocity in the main flow zone is twice that of the approach flow velocity in the fixed bed. But it is approximately the same as the incoming velocity in equilibrium scouring. The maximum turbulent energy appears to be mainly located in the backflow area of the fourth spur dike in the fixed bed, while the maximum value appears at the second spur dike head in the movable bed. Further, the shear stress decreases as scouring develops. Pearson correlation analysis was carried out between scour depth and shear stress. The analysis results are significantly correlated, indicating that the bed shear stress plays a prominent role in the scouring process. These discoveries can serve as a guide to determine the most reasonable spacing of spur dikes.

Estimation of maximum local scour depth around submerged spur-dike

2016 ◽  
pp. 193-199
Author(s):  
S.Y. Hao ◽  
Y.F. Xia ◽  
H. Xu
Keyword(s):  
Local Scour ◽  
Scour Depth ◽  
Spur Dike

Formula Type of Local Scour Depth on Spur Dike Nose

2014 ◽  
Vol 641-642 ◽  
pp. 271-274
Author(s):  
Qiang Ying
Keyword(s):  
Formation Process ◽  
Local Scour ◽  
Scour Depth ◽  
Calculation Methods ◽  
Spur Dike ◽  
Scour Hole ◽  
Main Factors ◽  
Formula Type ◽  
Suggested Formula

This passage introduces the formation process of scour hole, analyzes the main factors contributed to the local scour hole’s depth and classifies today’s calculation methods of scour depth into three categories. Then, given the conditions where those methods can be applied and drawbacks of those methods, this article also recommends some suggested formula in calculation.

scholarly journals Estimation of maximum scour depth near a spur dike

2016 ◽  
Vol 43 (3) ◽  
pp. 270-278 ◽  
Author(s):  
Manish Pandey ◽  
Z. Ahmad ◽  
P.K. Sharma
Keyword(s):  
Natural Phenomenon ◽  
Scour Depth ◽  
Flowing Water ◽  
Performance Indices ◽  
Spur Dike ◽  
Bed Erosion ◽  
River Bed ◽  
Spur Dikes ◽  
Dike Failure ◽  
Better Than

Scour is a natural phenomenon in rivers caused by the erosive action of the flowing water on the bed and banks. Spur dikes are constructed across the flow to protect the bank from erosion by shifting of the river away from the bank. The spur dike undermines due to river-bed erosion and scouring, which is generally recognized as the main cause of spur dike failure. In this study, accuracy of existing equations for the computation of maximum scour depth has been checked with available data in the literature and data collected in the present study using graphical and statistical performance indices. Three new relationships are also proposed to estimate the maximum scour depth and maximum scour length upstream and downstream of spur dike. This new relationship for maximum scour depth is shown to perform better than other existing equations.

scholarly journals Physical Modeling of Spatial and Temporal Development of Local Scour at the Downstream of Bed Protection for Low Froude Number

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 1041 ◽  
Author(s):  
Sung Won Park ◽  
Jin Hwan Hwang ◽  
Jungkyu Ahn
Keyword(s):  
Equilibrium State ◽  
Froude Number ◽  
Fixed Bed ◽  
Local Scour ◽  
Dominant Factor ◽  
Scour Depth ◽  
Dimensionless Time ◽  
Temporal Development ◽  
Low Froude Number ◽  
Bed Protection

Local scour at the downstream of the river bed protection is one of the most important parameters for the design criteria and sustainable management of the hydraulic structures. Previously, various researches on its process in the equilibrium state have been suggested with experimental and numerical approaches. In this study, relatively long-term laboratory experiments of local scouring at the downstream of fixed bed in an open channel were conducted with mono-granular sediment bed and analyzed about maximum scour depth and its temporal development. In particular, we conducted experiments with relatively low Froude number (less than 0.5) and their duration of tests was exceeded over 700 hours. We modified the relationship between the dimensionless time and length scales of the maximum scour depth of the local scour hole based on the turbulent shear layer thickness. A new functional relationship between dominant factors and the maximum scour depth in the equilibrium state were suggested and compared with previously suggested formula. Also, from the results by nonlinear regression, Froude number was founded as a dominant factor on the prediction of equilibrium maximum scour depth.

scholarly journals Improving the 2D Numerical Simulations on Local Scour Hole around Spur Dikes

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1462
Author(s):  
Chung-Ta Liao ◽  
Keh-Chia Yeh ◽  
Yin-Chi Lan ◽  
Ren-Kai Jhong ◽  
Yafei Jia
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Local Scour ◽  
Bridge Piers ◽  
Scour Depth ◽  
Foundation Design ◽  
Mobile Bed ◽  
Scour Hole ◽  
Scour Holes ◽  
Spur Dikes

Local scour is a common threat to structures such as bridge piers, abutments, and dikes that are constructed on natural rivers. To reduce the risk of foundation failure, the understanding of local scour phenomenon around hydraulic structures is important. The well-predicted scour depth can be used as a reference for structural foundation design and river management. Numerical simulation is relatively efficient at studying these issues. Currently, two-dimensional (2D) mobile-bed models are widely used for river engineering. However, a common 2D model is inadequate for solving the three-dimensional (3D) flow field and local scour phenomenon because of the depth-averaged hypothesis. This causes the predicted scour depth to often be underestimated. In this study, a repose angle formula and bed geometry adjustment mechanism are integrated into a 2D mobile-bed model to improve the numerical simulation of local scour holes around structures. Comparison of the calculated and measured bed variation data reveals that a numerical model involving the improvement technique can predict the geometry of a local scour hole around spur dikes with reasonable accuracy and reliability.

scholarly journals Prediction of time variation of scour depth around spur dikes using neural networks

2011 ◽  
Vol 14 (1) ◽  
pp. 180-191 ◽  
Author(s):  
Hojat Karami ◽  
Abdollah Ardeshir ◽  
Mojtaba Saneie ◽  
S. Amin Salamatian
Keyword(s):  
Neural Networks ◽  
Regression Model ◽  
Time Variation ◽  
Back Propagation ◽  
Maximum Depth ◽  
Scour Depth ◽  
Effective Parameters ◽  
Spur Dike ◽  
Feed Forward Back Propagation ◽  
Spur Dikes

The maximum depth of scouring around spur dikes plays an important role in the hydraulic design process. There have been many studies on the maximum depth of scouring, but there is little information available on the time variation of scour depth. In this paper, the time variation of scouring around the first spur dike in a series was investigated experimentally. Experiments were carried out in four different bed materials under different flow intensities (U/Ucr). To achieve a time development of scouring around the first spur dike, more than 750 sets of experimental data were collected. The results showed that 70–90% of the equilibrium scour depths were occurring during the initial 20% of the overall time of scouring. Based on the data analysis, a regression model and artificial neural networks (ANNs) were developed. The models were compared with other empirical equations in the literature. However, the results showed that the developed regression model is quite accurate and more practical, but the ANN models by feed forward back propagation and radial basis function provide a better prediction of observation. Finally, by sensitivity analysis, the most and the least effective parameters, which affected time variation of scouring, were determined.

scholarly journals Numerical scour modeling around parallel spur dikes in FLOW-3D

2017 ◽  
Author(s):  
Hanif Pourshahbaz ◽  
Saeed Abbasi ◽  
poorya taghvaei
Keyword(s):  
Numerical Model ◽  
3D Model ◽  
Flow Characteristics ◽  
3D Models ◽  
Scour Depth ◽  
Spur Dike ◽  
Accuracy Level ◽  
Bank Protection ◽  
Numerical Research ◽  
Spur Dikes

Abstract. Spur dikes are some structures which are built in the flow path with the aim of changing flow characteristics in order to bed and bank protection in rivers. These sudden changes in properties caused by the existence of spur dikes, produces erosion and sedimentation around them. In this paper, effects of series of parallel spur dikes have been investigated numerically. For this purpose, by using experimental and numerical research results from technical literatures, the numerical model conducted in FLOW-3D commercial software and the data were compared with experimental and SSIIM results. The results showed that Froude number and the ratio of U/Ucr affect the accuracy of the models. As a result, by discharge increasing, FLOW-3D models need to be calibrated again. Also, by using a calibrated FLOW-3D model, calculation accuracy of the scour depth at the bottom of the spur dikes becomes better and the accuracy level in the modeling of the surface morphology improves 7 percent more than SSIIM software in the bottom of the first spur dike, more than 80 percent at the bottom of the second spur dike and approximately 40 percent at the bottom of the last spur dike.

scholarly journals Local Scour Near Flexible Flow Deflectors

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 153 ◽  
Author(s):  
Liquan Xie ◽  
Yehui Zhu ◽  
Huang Li ◽  
Yan-hong Li ◽  
Yuanping Yang ◽  
...  
Keyword(s):  
Flow Field ◽  
Turbulent Energy ◽  
Local Scour ◽  
Scour Depth ◽  
Engineering Structures ◽  
Local Flow ◽  
Horseshoe Vortices ◽  
Bed Scour ◽  
Flow Deflector ◽  
Prone Posture

Rigid flow deflectors are usually used on water flow beds to protect engineering structures such as breakwater in coasts and to regulate flow routes in open channels. To reduce its side-effects, i.e., local scour at the toe of deflectors, a flexible flow deflector is proposed, and the corresponding local scour was investigated in this study. A flume experiment was conducted to investigate local scour. To show the advantage of flexible deflectors, a control experimental test was also conducted using a traditional rigid deflector under the same blockage area configuration and the same flow conditions. The flow field near the flexible deflector was also measured to reveal the local flow field. The results show that the bed-scour develops near the toe edges of both flexible and rigid deflectors, but the maximum and averaged scour depths for the flexible deflector are smaller. This advantage of flexible deflector in scour depth is mainly caused by its prone posture, which induces the upward stretching and enlarging horizontally rotating vortex and the upward shifted vertically rotating vortex. The former dissipates more turbulent energy and the latter results in smaller bed shear stress, which lead to smaller scour depth directly. In addition, the up- and down-swaying movement of the flexible deflector can also assistant to dissipate more turbulent energy, thereby damping the intense of the horseshoe vortices and thus weakening scour depth as well. The results of this study provide an elementary understanding on the mechanisms of a flexible flow structure and an alternative deflector-device to reduce scour depth.

scholarly journals Experimental study of local scour around T-shaped spur dike in a meandering channel

2020 ◽  
Author(s):  
Ravi Prakash Tripathi ◽  
K. K. Pandey
Keyword(s):  
Froude Number ◽  
Research Work ◽  
Local Scour ◽  
Scour Depth ◽  
Spur Dike ◽  
Meandering Channel ◽  
Work Related ◽  
Channel Bend ◽  
River Training ◽  
Training Structure

Abstract A spur dike is mainly constructed as a river-training structure and is primarily used to prevent bank erosion. The restriction to flow caused by the construction of a spur dike promotes local scour around the structure. In the case of a dike placed in a channel bend, the scour becomes more aggressive. The literature review found that the research work related to local scour around a spur dike located in a meandering channel is very limited or minimal. Therefore, an experimental investigation was conducted to study the local scour process around a T-shaped spur dike placed at different locations along the outer bank (or concave) of a reverse-meandering channel. Non-dimensionalized empirical equations for temporal and maximum local scour depth were developed as the function of the Froude number of approach flow and spur dike location. It is observed that local scour around the dike increases with the increase in Froude number and location in the meander (measured from the entry to meander). The formulation for the maximum scour depth was further evaluated with the experimental data related to the 180° bend, from literature, and it was found that the proposed equation's application is very much limited.

scholarly journals Numerical Investigation of the Combined Slot Effect on the Erosion Pattern Around a Combination of Spur Dikes in Series

2021 ◽  
Author(s):  
Khosrow Hosseini ◽  
Shahab Nayyer ◽  
Mehran Kheirkhahan ◽  
Sayed-Farhad Mousavi
Keyword(s):  
Flood Control ◽  
Effective Area ◽  
The Body ◽  
Scour Depth ◽  
Spur Dike ◽  
Bed Erosion ◽  
Geometrical Shapes ◽  
In Series ◽  
Spur Dikes ◽  
The Web

Abstract Modifying the river course for flood control, prevention of bed erosion, bank protection, and the regulation of river width are among the goals of spur dikes incorporation. The common spur dikes have simple (I), L and T geometrical shapes. The present research has been conducted to reduce the scour depth in front of the spurs dikes and improve the sedimentation conditions for the LTT combination of spur dikes in series by investigating different combinations of slots in the body of the spur dike; using numerical methods. The slot dimension was taken equal to 10% of the effective area of the spur dike body. Finally, the (LS-W-Wi, TS-W, TS-W-Wi) combination contained the slots in the web and wing of the first and third spur dike also the slot at the web of the middle spur dike was found as the best combination of slots. This combination conducted to reduce the scour depth about 6.8% and increase the deposition about 52% comparing by the spurs dikes without slots. Reducing the scour depth and increasing the sedimentation rate of materials between the spurs dikes. Also, the maximum scour depth decreases up to 20%. The results revealed that the presence of slots in spur dike structures and their different positions have complicated and considerable influences on the form and morphology of the erodible bed which could be the topic for further researches.

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