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Showing papers on "Groyne published in 2007"


Journal ArticleDOI
TL;DR: In this paper, a 3D and two-dimensional depth-averaged large-eddy simulations (LES) are presented for three different shallowwater flows involving large-scale horizontal structures: a mixing layer, the flow around a circular cylinder and the flow in a groyne field.
Abstract: Three-dimensional (3D) and two-dimensional (2D) depth-averaged (DA) large-eddy simulations (LES) are presented for three different shallow-water flows involving large-scale horizontal structures: a mixing layer, the flow around a circular cylinder, and the flow in a groyne field. The results are compared with each other and also with experiments. In the 3D-LES, most of the energy-containing turbulent motions, including the larger subdepth-scale motions, are resolved, while in the 2D-DA-LES the effect of the 3D subdepth-scale turbulence is represented by a quadratic bottom-friction model and a simple eddy-viscosity model. In the case of the mixing layer, an additional stochastic backscatter model is necessary to account for the energy transfer from the subdepth-scale turbulence to the 2D structures in order to generate the latter. The 3D-LES results are generally in good agreement with the experiments, including the evolution of the horizontal structures. The much more economic 2D-DA-LES are somewhat less realistic in detail but also produce results that are generally of sufficient accuracy for practical purposes.

106 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the behavior of the Currumbin Creek entrance and adjacent beaches from aerial photographs and numerical modelling, and found that during fair weather conditions, the sand transported by the longshore current is trapped by Currin rock groyne resulting in a negative sediment budget in Palm Beach.

58 citations


Journal ArticleDOI
TL;DR: In this article, large eddy simulation is used to investigate the dynamics of the main coherent structures present in the flow around two vertical submerged groynes situated in a long flatbed open channel.
Abstract: [1] Large eddy simulation is used to investigate the dynamics of the main coherent structures present in the flow around two vertical submerged groynes situated in a long flatbed open channel. The mass exchange processes between the embayment region and the main channel are investigated by studying the ejection of a contaminant introduced instantaneously inside the embayment. The instantaneous and mean structure of the horseshoe vortex system forming at the base of the upstream groyne and the bed shear distributions that determine the evolution of the scour in the groyne region are investigated. It is found that the amplification of the bed shear stress in the accelerating region around the tip of the upstream groyne is around one order of magnitude larger relative to the mean bed shear stress in the incoming flow. Analysis of the instantaneous flow fields shows that the eddies that are shed inside the horizontal and vertical detached shear layers play an important role in controlling the mass exchange at the lateral and roof interfaces. It is found that most of the pollutant leaves the embayment through the roof and bottom lateral sections. The overall mass exchange process is qualitatively different and substantially accelerated compared to the case when the groynes are emerged. However, it is shown that similar to the emerged case, the decay of the mass of contaminant within the embayment cannot be characterized by a unique value of the exchange coefficient used in simple dead zone theory models.

57 citations


Proceedings ArticleDOI
08 May 2007
TL;DR: In this paper, the spatial distribution of the three-dimensional flow field through a series of submerged groynes in a 90o channel bend is mapped and the impact on the flow field of subtle differences in barb geometry are examined.
Abstract: Barbs (or submerged groynes) are low-profile linear rock structures that are primarily used to prevent the erosion of stream banks. They are a variation of a groyne, similar to spur dikes and bendway weirs. Barbs are typically anchored, in series, to the outside bank in stream bends and extend in an upstream direction from the bank into the flow. This configuration redirects flow away from the outer stream bank and disrupts the velocity gradient close to the outer bank, encouraging sediment deposition adjacent to the barb. These interactions between the flow pattern and the sediment transport around the barb prevent erosion of the bank. Furthermore, vortices generated by the barb create local scour holes that can enhance aquatic habitat. A three-dimensional numerical model, Sediment Simulation in Intakes with Multiblock option (SSIIM), was used to examine the turbulent flow field and associated scour and depositional patterns due to a series of barbs in a mobile-bed channel bend. Previous physical model observations were used for model calibration and verification. Barb design was optimized to minimize scour. The parameters considered in the optimization were channel bend angle, barb alignment angle, and barb spacing. In this paper the spatial distribution of the three-dimensional flow field through a series of barbs in a 90o channel bend are mapped and the impact on the flow field of subtle differences in barb geometry are examined. Special emphasis is placed on the influence of barb design on secondary currents in the meander bend and the generation of three-dimensional vortices, and the consequent impact on scour.

8 citations


01 Jan 2007
TL;DR: In this article, the authors considered the case of flow separation and non-hydrostatic effects of flow over oblique weirs and proposed a simple analytical approach for flow separation.
Abstract: At high water stages the flow in groyne fields is highly affected by the water flowing over the groyne. For those conditions the groyne acts as an (im)perfect weir. In a similar way local elevations in the flood planes can be considered as weirs. The arbitrary orientation of those obstacles with respect to the flow prohibits the use of straightforward weir formulations. By considering the generic case of the flow over oblique weirs, a simple analytical approach already gives good insight and acceptable estimates, whereas a 3D numerical model clearly shows the complexities of flow separation and non-hydrostatic effects.

3 citations


01 Jan 2007
TL;DR: In this article, the effect of softwood vegetation on groyne field morphology is described and the morphological development of three test locations along the River Waal have been determined based on elevation measurements from 1990 until 1995 and newly conducted measurements from 2005 and 2006.
Abstract: Softwood vegetation can be found within a significant number of groyne fields along the River Waal. Vegetation is commonly known to decrease flow, attenuate waves, alter sediment properties and trap sediment. The total effect of these characteristics on groyne field morphology however is still unknown. Within this thesis the effect of softwood vegetation on groyne field morphology is described. The morphological development of three test locations along the River Waal have been determined based on elevation measurements from 1990 until 1995 and newly conducted measurements from 2005 and 2006. At each of the test locations one groyne field has been used for the plantation of willows while the upstream and downstream groyne field has been used as reference. At each location the species, common osier (Salix viminalis), purple willow (Salix purpurea) and gray willow (Salix cinerea) were planted in an alternating pattern on the upper bank of the study groyne field. From these species the survival percentages and yearly averaged mortality rates have been determined. Furthermore, hydraulic conditions (water level and discharge) have been determined at each location from 1990 until 2005 at each location. These conditions have been determined by using a 1D-model, SOBEK. The data obtained from elevation measurements has been used to create detailed Digital Elevation Models to describe the morphological situation at the time of measuring. In order to create these models, several interpolation methods have been assessed to determine which technique would be best suited for this study. Elevation Difference Maps and series of Riverbank Profiles were derived from the Digital Elevation Models. These were used to describe the morphological development per location over time. Volumetric calculations were also made to determine the effect on the total sediment balance within each groyne field. At each of the three test locations, the presence of softwood vegetation has caused erosion of the lower bank and accretion at the upper bank. The morphological development within the corresponding reference groyne fields differ from the test groyne field but are consistent with each other. It can therefore be concluded that the found effect at the test locations is induced by the presence of softwood vegetation. From the calculated volumetric differences, it can be seen that at locations were erosion has taken place at the reference groyne fields the presence of vegetation at the test groyne field has caused less erosion compared to the reference fields. At the locations were sedimentation has taken place at the reference groyne fields, the presence of softwood vegetation within the study groyne field has caused erosion. The total of the processes and factors, which are mentioned throughout this report to have an effect on groyne field morphology, are bundled into a conceptual riverbank model for groyne fields with the presence of softwood vegetation. From this model a list of desired improvements for future riverbank models has been derived. Chapter:

2 citations


Journal ArticleDOI
TL;DR: In this article, a numerical analysis and a laboratory experiment were carried out in respect to an open channel flow field with a movable bed in which a permeable groyne was installed.
Abstract: In this study, a numerical analysis and a laboratory experiment were carried out in respect to an open channel flow field with a movable bed in which a permeable groyne was installed. By comparing the agreement between the analysis and the experiment, the influence of the permeable groin to the open channel flow and movable bed erosion were discussed. The numerical method was expected to provide knowledge to the design of river structure such as permeable rubble mound groyne.

1 citations



Patent
27 Nov 2007
TL;DR: The groyne as mentioned in this paper consists of a main body with a slope, the crown of this body being below high tide level but above low tide level, as well as a row of spaced apart flow resistance bodies such as gabions.
Abstract: The groyne (1) comprises a main body (2) with a slope, the crown of this body being below high tide level but above low tide level, as well as a row of spaced apart flow resistance bodies such as gabions (3). The total height of the groyne is below high tide level. Independent claims are also included for the following: (1) Construction method for the groyne, comprising forming a geotextile-reinforced main body which extends into a body of water from a river bank, cladding the body with a mat of concrete blocks (4) having a low hydraulic roughness, and placing a row of flow resistance bodies on top of the crown of the body; and (2) Gabion for the groyne, preferably provided with a means for fastening it to the groyne body.

1 citations


Journal ArticleDOI
TL;DR: In this article, the mean and coherent flow structures around a single groyne under emerged and submerged conditions were experimentally discussed and a scaled and schematized model was implemented and experiments were conducted by means of surface flow visualization technique and Particle Tracking Velocimetry (PTV).
Abstract: Groynes have been used for the stabilization of banks and for creating a navigation channel by confining the cross-sectional area, especially for large European and Japanese rivers. Therefore, turbulent flows and transport phenomena in groyne fields have paid attention to the appropriate design for bank protection and obtainment of enough depth in the main channel as well as the proper environment for ecosystems. In the present study, mean and coherent flow structures around single groyne under emerged and submerged conditions were experimentally discussed. In order to investigate the flow pattern around the single groyne, a scaled and schematized model was implemented and experiments were conducted by means of surface flow visualization technique and Particle Tracking Velocimetry (PTV). Furthermore, analytical techniques of proper orthogonal decomposition (POD) are applied to reveal typical pattern of coherent structures.