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In this research, complementary numerical and experimental physical models were conducted to investigate flow parameters around an isolated permeable spur dike using ANSYS FLUENT ver. 16.1 software. The volume of fluid method VOF with the help of CFD technique and the κ − ε turbulence model was used to simulate the complex free-surface flow by applying a geometric reconstruction scheme. Two different mediums with different porosities were used, namely, gravel and glass beads. It was found that, for low flow rate values, there are no significant changes in the water profiles in both longitudinal and lateral directions for both media. Although for high flow rate values, the differences tend to be clearer. Results showed that there is a slight effect of the medium's properties if the dike width is less than 1/3 of width of the channel, in particular with low flow rate values. Good agreement was observed between the computational and the measured results for the water surface profiles. Also, there is an exact match between the lateral velocity distribution of gravels and glass beads. Downstream the dike, the lateral velocity profiles exhibit an S shape curve due to high velocity in the free flow and small flow velocity behind the porous dike. The results show good agreement between the CFD results and the experimental observations of the water surface profiles and velocity distribution according to the statistical analysis using some standard indexes error. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

With the advancement in the science of engineering, bridge piers scouring has become a well-known phenomenon, and engineers have always been making efforts to counter such a destructive phenomenon. One of the methods used to reduce scouring around the bridge pier is application of other hydraulic structures which influence the amount of scouring in the flow path, such as submerged vanes, collars, riprap, and spur dike. This study aims to analyse the efficiency of rigid T-shaped spur dike in decreasing the scouring around bridges with a 90° pier in a 180° channel with a sharp bend. Experiments were carried out with the installation of a spur dike at the upstream pier on both inner or outer banks, in different positions, under clear water conditions, and the efficiency of the spur dike for reducing the scouring was compared with the control experiments. The results showed that the installation of the T-shaped spur dike on the outer bank significantly augmented the bridge pier scour reduction, and the greatest influence resulted from installation of a spur dike at 70° position on the outer bank, which reduced the scouring by 50% compared to a case of no spur dike installed. [ABSTRACT FROM AUTHOR]

This study presents the influence of cohesion on scour at wake region of the partially submerged spur dikes embedded in cohesive sediment mixtures consisting of clay-gravel and clay-sand-gravel. The experimental results revealed that the development of scour hole and scouring process around spur dike in cohesive sediment containing sand and gravel were considerably different than that of cohesionless sediments. The geometry and process of scour at the spur dike wake region were found to vary with unconfined compressive strength and clay content present in the mixtures of cohesive sediment. The scour depth decreases drastically with an increase in clay percentage and unconfined compressive strength of the mixtures of cohesive sediment. Using dimensional analysis, equations have been presented for the assessment of scour depth in the wake region of spur dikes embedded in the mixtures of gravel-clay and gravel-sand-clay sediments. [ABSTRACT FROM AUTHOR]

Scour is a natural process in rivers initiated by the erosive action of the activated water. Spur dikes are built across the flow to defend the stream erosion and facilitate the shifting of the river away from the bank. The spur dike weakens due to stream bed scouring and erosion, which is usually documented as the key reason of spur dike failure. Failure of spur dikes due to local scour has inspired many investigators to discover the cause of scouring phenomenon and to forecast the temporal and maximum scour depth near spur dikes. In this paper, a review of the scour around spur dikes with all possible aspects, like temporal and maximum scour depth, flow pattern, parameters affecting scour phenomenon has been discussed briefly. [ABSTRACT FROM AUTHOR]

Turbulent flow structures forming around isolated spur dikes in a horizontal channel are investigated in this study. In the analysis detached eddy simulation is used under fully turbulent incoming flow conditions at a channel Reynolds number of 45,000. Changes in the structure of the horseshoe vortex system, bed shear stress and pressure standard deviation on the bed are investigated for three different spur dike lengths. In all of the cases the main horseshoe vortex undergoes bimodal oscillations, which leads to an amplification in the turbulence quantities such as turbulent kinetic energy and pressure fluctuations along its axis. The main horseshoe vortex disappears over a much shorter distance in the flow direction for the short spur dike than those of medium and long spurs. Large bed shear stress values and pressure standard deviation values observed around the tip of the spur dike, beneath the upstream part of the main horseshoe vortex and beneath the separated shear layers increase with the increasing length of the spur dike. Different from the long and medium spur dike, in the short spur dike case, it is shown that the secondary horseshoe vortex is as coherent as the main horseshoe vortex and it contains bimodal oscillations together with the main horseshoe vortex. [ABSTRACT FROM AUTHOR]

The turbulent flow structures around an isolated spur dike located at three different approach flow angles are investigated. Detached eddy simulation is used at a channel Reynolds number of 45,000. Experimental velocity measurements were also conducted using acoustic Doppler velocimetry for validating the simulations. It is found that the size and orientation of the horseshoe vortex system change considerably with the approach flow angle. The main necklace vortex is largest in size and most coherent for 90°. Within this orientation it has larger amplitude bimodal oscillations compared to the 60° and 120° cases. A new scour mechanism is defined for the 60° case which is expected to generate more scour upstream of the spur dike. The possible scour area around the spur dike is found to be the maximum in the 90° case which is roughly by 15% larger than that of the 120° case. [ABSTRACT FROM PUBLISHER]

In the present study, flow patterns around a single spur dike (also termed a groyne) with free-surface flow was simulated using a numerical model known as Fluent. The model solved the fully three-dimensional, Reynolds-averaged Navier-Stokes equation to predict flow near the structure where three-dimensional flow is dominant. To treat the complex free-surface flow, the volume of fluid method with geometric reconstruction scheme was applied and turbulence was simulated using standard [image omitted] equations. In this research work, both a structured and an unstructured mesh were used and the density of the mesh spacing was selected the highest near the walls and also free surface to obtain more accurate results. Comparison of free surface and velocities of 3D model showed good agreement with three experimental flume data obtained by other researchers. The reattachment length for various conditions was computed using the numerical results and flow pattern was presented for repelling, attracting and vertical spur dikes together. Also, bed-shear stress distribution was presented and the effects of flow discharge and the length and angle of the spur dike upon the bed shear-stress distribution were evaluated. [ABSTRACT FROM AUTHOR]