Spur Dike Research Articles

Flow Control in a Rectangular Open Channel using Two Impermeable Spur Dikes: A Numerical Study

The present study examines how adjusting vegetation patches in a rectangular open channel with two impermeable spur dikes alters the displacement of the recirculation region. The Reynolds stress turbulence model is implemented via the 3D numerical code FLUENT (ANSYS). Mean stream-wise velocity profiles were drawn at selected positions and at mid of flow depth i.e., 3.5 cm, a horizontal plane is cut through the open channel for analyzing velocity contours and streamline flow. The findings indicate that the stream-wise velocity profiles showed fluctuations in the presence of different shapes and arrangement of cylindrical patch discussed and the maximum velocity within the field of spur dike is of the order of 0.018 m/s due to the prism shape. By changing the position of the cylindrical patch, the location of the recirculation region displaces within the field of impermeable spur dike.

Riverbed Morphologies Induced by Local Scour Processes at Single Spur Dike and Spur Dikes in Cascade

Spur dikes are elongated structures extending from banks into rivers that mitigate erosion by forcing the flow away from the bank. The research on grouped spur dikes is insufficient in comparison with those on isolated spur dikes. Most of the studies focus on the maximum scour depth, omitting the bed morphological changes induced by local scour processes. Moreover, as yet, there is no established procedure for predicting the scour depth around spur dikes. This study aims to provide insights into the temporal and spatial morphological patterns around a single spur dike and spur dikes in cascade (three, five, and seven, consecutively). Experiments (of up to 318 h) were performed on a rectangular straight channel with dimensions of 20 m (length) × 1.0 m (width) × 1.0 m (depth). Nearly uniform sand with median grain size of 1.7 mm and sediment gradation of 1.5 was used for the mobile bed. The spacing between the elements for the spur dikes in cascade was 3b, where b is the spur dike width. All runs were conducted under a clear-water regime and steady flow conditions. Some limitations of the formulas for the equilibrium scour depth at the first spur dike reported in the literature were emphasised, with underestimations up to 160% and overestimations up to 200% at the earlier scour stages. The temporal evolution of the scour depth at the first spur dike was satisfactorily predicted with a correlation coefficient of 0.91. The scour processes at the other spur dikes were delayed and started at a dimensionless time greater than approximately 103. However, the scour rates increased to a high degree, with the scour depths tending to match those at the first spur dike.

Experimental and numerical study on the flow characteristics around spur dikes at different length-to-depth ratios

A spur dike is an in-stream structure, one end of which is situated on the bank of a channel, while the other extends into the current. Its primary functions include protecting stream banks and enhancing aquatic habitats. The motivation of this study stems from the hypothesis that a wake parameter, defined as the product of the length-to-depth ratio of spur dikes and the bottom friction factor, serves as the key parameter in characterizing the flow pattern around these structures. The objectives of this study are two-fold: (1) to determine the critical value of a wake parameter for the transition from three- to two-dimensional flow fields around spur dikes, and (2) to examine the bed shear stress distributions around spur dikes with varying length-to-depth ratios. Flow visualization experiments and large-eddy simulations (LESs) were conducted with length-to-depth ratios ranging from 1 to 7.5, corresponding to wake parameter values between 0.005 and 0.075. The experimental and numerical results revealed various flow structures around and in the wake of the spur dike. When the length-to-depth ratio was close to 1, the two- and three-dimensional flow patterns coexisted around the spur dike. However, as the length-to-depth ratio increased, the three-dimensional flow structures diminished and the two-dimensional flow structures became more pronounced. For an length-to-depth ratio of 7.5, the flow pattern showed fully two-dimensional structures featured by an upstream and a pair of downstream recirculation regions with negligible secondary flows, a horseshoe vortex, and a free-surface vortex. A horseshoe vortex system contributed to a significant increase in both mean and root mean square bed shear stresses near the tip of spur dikes, especially when the wake parameter values were low. The upstream recirculation zone was associated with very low bed shear stress at high values of the wake parameter. The results of this study corroborated that the flow around the spur dikes becomes fully two-dimensional when a wake parameter exceeds a critical value of approximately 0.04.

Investigation on the influence of spur dikes on the weighted usable area for the two native species in a city-crossing river

Spur dikes, mainly for regulating water flow and protecting river banks in the past, were found recently to have the ability to increase the fish physical habitat and improve aquatic system. However, the effect of spur dikes on aquatic system was generally ignored previously, and the studies on the influence of spur dikes on improving specific native fish physical habitat are still rare. This study reports a numerical investigation for the effects of spur dikes on the physical habitat and the minimum ecological flow in the Jinjiang River. Three spur dikes are placed along the inner bend in the study reach and two fish species of the Pelteobagrus fulvidraco and carps are selected as the target species. Two-dimensional water depth and velocity field are simulated in different discharges and the results are used to predict the corresponding weight use area (WUA). The differences of WUA before and after the building of spur dikes for the two selected fish species show that spur dikes have a significant effect on the physical habitats. And the minimum ecological flows from the instream flow increment approach are different for the two objective fish species and are also considerably impacted by spur dikes.

Integrative Study on Flow Characteristics and Impact of Non-Submerged Double Spur Dikes on the River System.

The flow characteristics around non-submerged spur dikes continuously placed in the channel on the same side with orthogonal angle to the wall were investigated by numerical simulations and experimental measurements. Three-dimensional (3D) numerical simulations with the standard k-ε Model for incompressible viscous flow based on finite volume method and the rigid lid assumption for free surface treatment were conducted. A laboratory experiment was applied to verify the numerical simulation. The experimental data indicated that the developed mathematical model can effectively predict 3D flow around non-submerged double spur dikes (NDSDs). The flow structure and turbulent characteristics around them were analyzed and it was found that a distinct cumulative effect of turbulence exists between the dikes. By examining the interaction rules of NDSDs, the judgment criterion of spacing threshold was generalized as whether velocity distributions at the cross-sections of NDSDs along the main flow approximately coincided or not. It can be used to investigate the impact scale of the spur dike groups on the straight and prismatic channels and it is of great significance for artificial scientific river improvement and the assessment of river system health under human activities.

Experimental Analysis of 3D Flow Structures around a Floating Dike

Floating dikes have several advantages over spur dikes including less influence on riverine sediment transport, bed topography, and ecosystems, and a good adaptability to fluvial conditions. Despite these advantages, floating dikes have not been used in many river regulation schemes due to the limited understanding of the 3D flow structures around floating dikes. In this study, a series of experiments were conducted to investigate the 3D flow structures around floating dikes. Results show that, after installing a floating dike on one side of a flume, the surface water flow is deflected to the opposite side of the flume, and a backflow develops around the outer and downstream side of the dike, where both the vertical turbulent intensity and the absolute magnitude of the Reynolds stress are relatively large. Due to the blocking effect of the dike, the cross-sectional area decreases, causing an increase in velocities below and alongside the dike, as well as a decrease in velocities upstream of the dike. Increasing the submerged depth or length of the dike results in an increase in flow velocity adjacent to the dike, as well as an increase in the vertical or lateral scale of the backflow. On the contrary, increasing the dike thickness leads to a weakening or disappearance of the backflow, along with a decrease in the acceleration rate of flow adjacent to the dike.

Hyporheic exchange law driven by spur dikes: Numerical modeling

The study of hyporheic exchange and the temperature response law driven by spur dikes is helpful to promote the protection of ecological river environments. Taking the river channel course with a spur dike as the research object, the numerical simulation method was used to study the influence of the river width narrowing rate (L/B), spur dike angle (θ), surface water velocity (U), and hydraulic conductivity (K) on the hyporheic exchange characteristics and the temperature response of the hyporheic zone. Research shows that the degree of hyporheic exchange and the spatial range of the temperature response of the hyporheic zone are positively correlated with the river width narrowing rate, surface water velocity and hydraulic conductivity and negatively correlated with the spur dike angle. The temperature response law of the hyporheic zone is affected by spur dikes in different spatial locations in the following ways, from the cross-section, the upstream response area of the spur dike deepens near the dam bank, while the downstream response area deepens on the other side of the spur dikes, and the downstream response area affected by spur dikes is significantly larger than the upstream response area in the vertical range. From the side section, the response area of the curved boundary appears around the spur dike in the central section of the river, and the curvature radius of the response area of the curved boundary around the spur dike in the side section near the dam is smaller. From the longitudinal section, the sensitivity of the temperature response of the shallow section is significantly stronger than that of the deep section. Consequently, we found that the hyporheic exchange law driven by spur dikes. We offer recommendations for future studies seeking to choose the reasonable structure of the spur dam in practical engineering, and optimize the design of the spur dam.

Transport Dynamics of Large Wood in a Stream Channel Affected by Spur Dikes

AbstractThe damage to river engineering structures induced by large‐wood (LW) jams is one of the significant problems in river management. For example, typical bridge damage in alluvial areas in Japan, such as wash away, is often caused by the accumulation of large wood materials. The densely transported large wood pieces are an important factor in the accumulation process. We investigated the influence of local flows generated by hydraulic structures on the initial stage of the concentration of large wood pieces. First, we experimentally investigated the flow structures generated by spur dikes in a 0.6 m wide channel and the trajectory of large wood pieces. Then, we numerically investigated the influence of external force on the transport mechanisms of large wood pieces. We employed a simplified Basset‐Boussinesq‐Oseen model to evaluate each term of the momentum equation of the particles and calculated the trajectories of the wood pieces previously observed experimentally. The results showed that the transported large wood pieces were concentrated in low‐vorticity regions of the water surface. This tendency was more prevalent in short pieces (10 mm) than in long pieces (40 mm) because the influence of the relatively small‐scale patterns of the pressure gradient of the surrounding water surface might be spatially averaged for long pieces. This tendency has not been explicitly elucidated in previous works; thus, this knowledge is expected to be key in controlling LW transport, such as detecting the possible regions where LW jams occur or designing efficient inlet sections of LW retention facilities.

Optimization of the performance of riprap apron to protect spur dikes against scouring using Taguchi and grey relational analysis methods

Optimization of the performance of riprap apron to protect spur dikes against scouring using Taguchi and grey relational analysis methods

Experimental Study on the Local Scour of Submerged Spur Dike Heads under the Protection of Soft Mattress in Plain Sand-Bed Rivers

Submerged spur dikes are widely applied in the channel regulation structures of plain sand-bed rivers such as the lower reaches of the Yangtze River; thus, the issue of local scour protection near regulating structures is especially important for structure design engineering. To further scientific research on the local scour of submerged spur dike heads, we investigated rulers describing the variance of the incoming flow dynamic, scale of the spur dike body, width of river bottom protection, etc., responding to the maximum local scouring depth of a submerged spur dike and the distance between the submerged spur dike and dam axis under the conditions of river bottom protection. According to principles of dimensional analysis, we established computational formulas for the maximum local scouring depth of a submerged spur dike and the distance between the submerged spur dike and dam axis, with consideration of bottom protection works for the remaining soft mattress. These research results not only enrich existing research on the calculation of local scour of channel-regulating structures, but they are also a relevant technical reference for the design of water conservancy and waterway engineering.

Gene-expression programming for scour around spur dike

Spur dikes are hydraulic structures construct in the river or channel and help for saving the bank from erosion, deepen the upstream channel and the habitat present on the dyke of the river. Due to the importance of river dike as a natural habitat for microorganisms, researchers are attracted to the scour formed around the spur dike; however, the straight channel spur dike is studied most in current days, along with the curved channel or bends. The current paper deals with expanding GP. The GEP is an alternative approach in the way of modelling, which predicts the maximum scour depth. The introduced GEP model may apply to various boundaries with the part-full flow, and the approach gives excellent results compared to pre-existing data.

Discussion of “Prediction of Maximum Scour Depth near Spur Dikes in Uniform Bed Sediment Using Stacked Generalization Ensemble Tree-Based Frameworks” by Manish Pandey, Mehdi Jamei, Masoud Karbasi, Iman Ahmadianfar, and Xuefeng Chu

Discussion of “Prediction of Maximum Scour Depth near Spur Dikes in Uniform Bed Sediment Using Stacked Generalization Ensemble Tree-Based Frameworks” by Manish Pandey, Mehdi Jamei, Masoud Karbasi, Iman Ahmadianfar, and Xuefeng Chu

Discussion of “Prediction of Maximum Scour Depth near Spur Dikes in Uniform Bed Sediment Using Stacked Generalization Ensemble Tree-Based Frameworks” by Manish Pandey, Mehdi Jamei, Masoud Karbasi, Iman Ahmadianfar, and Xuefeng Chu

Discussion of “Prediction of Maximum Scour Depth near Spur Dikes in Uniform Bed Sediment Using Stacked Generalization Ensemble Tree-Based Frameworks” by Manish Pandey, Mehdi Jamei, Masoud Karbasi, Iman Ahmadianfar, and Xuefeng Chu

Gene-expression programming for scour around spur dike

Gene-expression programming for scour around spur dike

Experimental Study on the Influence of New Permeable Spur Dikes on Local Scour of Navigation Channel

The depths and areas of the scour holes around spur dikes are the most concerning issues regarding spur dike design. In this study, using a moving bed experiment, the influence of traditional rock-fill spur dikes and new permeable spur dikes with different permeabilities on riverbed scour under unsteady flow was studied, and the spatial characteristics of scour holes at dike heads were analyzed. The results show that with increases in the permeability coefficient of the spur dike, the depth and area of the scour hole at the dike head gradually decreases; however, when the permeability coefficient is more than 17.6%, the depth and area of the scour hole downstream of the dike body increases with an increase in the permeability coefficient. According to comprehensive evaluation, when the water permeability is 17.6%, the stability of the spur dike is at its best. The maximum depth of the scour hole at the dike head is affected by factors such as the spur dike permeability coefficient, effective scouring time, and width bottom protection structure. On this basis, a new formula for calculating the maximum depth of the scour hole at a dike head is proposed. These research results will be beneficial to the reliability of spur dikes and the sustainability of navigation channels.

Investigation of Flow Dynamics Around a Combination of Different Head Shapes of Spur Dikes

Investigation of Flow Dynamics Around a Combination of Different Head Shapes of Spur Dikes

Using combined slots as a new approach for optimizing erodible bed changes around the spur dikes in series

ABSTRACT The common spur dikes, which are used for river path control and bank protection, are utilized without any slots or with additional structures such as a collar or vane. The present research has been conducted to optimize the slot position in the spur dikes’ body, reduce the scour depth, and improve the sedimentation conditions using the CFD model. The numerical result was compared with the Nayyer et al. 2019. A numerical and experimental investigation of the effects of combination of spur dikes in series on a flow field. Journal of the Brazilian Society of Mechanical Sciences and Engineering, 41(6), 1–11) experimental outcome. Results showed that 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, and the slot at the web of the middle spur dike was found as the best combination of slots under clear-water conditions. This combination was conducted to reduce the scour depth by 6.8% and increase deposition by 52% compared to the spur dikes without slots, which causes reducing scour depth and an increase in the sedimentation rate of materials between two consecutive spur dikes in series. Also, the maximum scours depth decreases by up to 20%. The results revealed that the presence of slots in spur dike and their different positions have complicated and considerable influences on the form and morphology of the bed.

Flow behaviour concerning bank stability in the presence of spur dike – A review

Abstract Flow in streams and rivers typically erodes the banks, causing channel bank migration laterally, resulting in loss of nearby land, modification in channel morphology, excessive sediment transport, and water quality degradation. A spur dike is a hydraulic structure placed at the channel bank projecting outward to guide or divert the flow away from the bank, thus protecting it from erosion. The stability of the riverbed and banks is influenced by turbulent characteristics such as three-dimensional velocity distribution, turbulent kinetic energy, Reynolds shear stress, turbulent intensity, and bed shear stress. The researchers found that these turbulence parameters are instrumental in sediment movement along the channel's bed and from its banks. Spurs dikes are a significant river training structure provided along the river bank to protect from erosion. Several aspects related to spur dikes, such as their geometry, physical features, design considerations, flow and scour patterns, etc., are critically reviewed in this paper. Despite the numbers of literature in the field of turbulent characteristics and scour depth around spur dike, the role of vegetation and the effect of seepage around spur dike still remains an unexplored area. These knowledge gaps of spur dikes in field conditions are discussed for future studies.

Hydrodynamics of tidal bore overflow on the spur dike and its influence on the local scour

In estuaries with strong tidal bore, the scour behind the spur dike induced by tidal bore overflow has significant influence on the dike safety. In this study, an experiment study of the local scour induced by tidal bore overflow behind the spur dike was carried out in a physical flume. In addition, the process of the tidal bore overflow on the dike was numerically simulated with the boundary generation method. The stable overflow water depth on the spur dike (hts), unit overflow discharge (qts) and the scour hole characteristics were analyzed based on the experimental and numerical results. It is found that the relative stable overflow water depth (hts/h1) increases with the increase of the Froude number after bore (Fr1) and decreases with the increase of relative dike height (hd/h1). While the relative stable unit overflow discharge (qts/q1) is mainly affected by the relative dike height. Additionally, the results of scour pit behind the spur dike show that the scour depth (s/h1) is directly proportional to the relative current intensity (u1/uc) and the dike height (hd/h1), but inversely proportional to the water depth before bore (h0/h1). An empirical equation for predicting relative maximum scour depth is obtained by fitting the experimental results and the field measured data, and the prediction accuracy is within 30%. The conclusions of this paper can provide technical support for the engineering design and operation evaluation of spur dikes in estuaries with the strong tidal bore.

Numerical modelling of local scour around a spur dike with porous media method

ABSTRACT A 3D numerical model is developed to investigate the flow motion and sediment transport around a spur dike. In this model, fluid motion is described by the Navier–Stokes equations, adopting large eddy simulation to capture turbulent transport and dissipation. The spur dike and sand bed are treated by the porous media method. The suspended load concentration and the bed load transport rate is calculated separately, and then the bed variation is updated using the mass-balance equation. A series of flume experiments are employed to validate the model’s performance before being applied for the case of partially emergent spur dikes and submerged spur dikes, respectively. Detailed analyses on the spatial-temporal variation of flow intensity, sediment concentration and shapes of scour holes are made, based on which some innovative findings are discussed such as the scouring process patterns, as well as the influence of flow conditions on the maximum scour depth and location, and then useful engineering suggestions are provided to improve structural safety.