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Groyne

About: Groyne is a research topic. Over the lifetime, 397 publications have been published within this topic receiving 4549 citations. The topic is also known as: groin & Breakwater.


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01 Jan 2021
TL;DR: In this paper, the authors compare the effect of lowering the crest of groynes in the Dutch rivers with the aim of lower the backwater effect of groyne lowering under high water levels.
Abstract: Currently multiple projects investigate the effect of lowering the crest of groynes in the Dutch rivers with the aim to lower the backwater effect of groynes under high water levels. There is a major uncertainty however in the modelling of groynes, and therefore in the prediction of the effect of groyne lowering. Currently submerged groynes are modelled subgrid as weirs. The flow processes differ however between groynes and weirs as discharge over a groyne is not purely defined by the contraction and expansion over the groyne, but also by lateral shear and interaction with the surrounding main channel and floodplain. The result is a lower resistance of the cross section than expected from weir modelling. For this reason a numerical investigation was started, comparing the modelling of groynes as different subgrid weirs in a 2D model and the modelling of groynes included in the bed topography in a 3D (non-)hydrostatic model. There were large differences between all different methods of groyne modelling. Furthermore the available experimental data did not suffice to explain the differences. For that reason a new physical model has been set up in the Delft University of Technology, at the hydraulic laboratory of the Faculty of Civil Engineering and Geoscience. The experiment includes a 1:30 scale model of a representative transect of the Waal river. The model is 5 m wide and 30 m long and includes 6 groynes and 5 groyne fields. It further includes a part of the main channel at one side and a part of the floodplain at the other side of the groyne fields. Gravel is fixed to the bed to ensure hydraulically rough flow conditions. In the experiment many measurements were done. The first aim of the measurements was to obtain a good spread of points to validate numerical models on. The second aim was to gain insight in the different flow processes in order to describe the differences between groyne and weir flow and quantify the resistance groynes have on a flow. An important observation was the existence of a region of low flow, at the tip of the groyne. The observation indicates a complex three-dimensional flow which effectively redistributes discharge over the transverse. The contribution of this flow to the two-dimensional momentum balance is then directly as a secondary circulation and indirectly by alternating the distribution of discharge. Complex flow furthermore invalidates the hydrostatic pressure assumption. The observed flow needs further investigation with either more accurate measurement devices or in a 3D non-hydrostatic model. Another observation includes the contraction and expansion of flow over the groyne crest. The expansion of flow over the main body of the groyne seems comparable to the expansion of flow over a weir, which can be predicted as Carnot head losses. The observation of expansion losses is however clouded by other flow processes, such as bed shear stress, the lateral flow around the groyne and possible three-dimensional processes induced by the groyne tip, so that the observed head loss over the groyne is only partially explained by weir-like expansion losses. The comparability between groyne flow and weir flow does not seem to hold at the groyne tip, where no separation of flow is observed. Measurements were performed 10 cm away from the transition between the groyne tip and main body of the groyne. This means that at full scale there is a region of 3 m on either side of this geometrical transition where the transition lies between weir-like overflow and non-weir-like overflow. With the here performed simulations it is possible to adapt weir head loss formulas on the observed head losses over groyne. It should be possible to validate a three-dimensional non-hydrostatic model, which can further quantify the effect of three-dimensional flow and differentiate the different contributions to groyne head loss. Based on these models proper tuning parameters can be chosen to represent the complex flow in a two-dimensional model and separately model the weir-like expansion.
Journal ArticleDOI
01 Jun 2020
TL;DR: In this paper, a new solution using ultra-high performance concrete (UHPC) sheet piles was a hard wall structure combined with gabion groyne dams for the purpose of shore protection, sand accretion, and tourist beach creation.
Abstract: A new solution using ultra-high performance concrete (UHPC) sheet piles was a hard wall structure combined with gabion groyne dams for the purpose of shore protection, sand accretion, and tourist beach creation was proposed in this study. The proposed approach was then applied to meet the both shore protection and sandy beach generation requirements of private Rung Duong resort project in Ba Ria-Vung Tau, Vietnam. The UHPC sheet piles reinforced by fiber reinforcement polymer (FRP) installed in form of a vertical wall were designed and constructed for the shore protection purpose. Together with the later built gabion groyne dam system, the combined structure brought a very good coastal protection effect. As a result observed from Rung Duong resort, the shoreline was pushed back out very far from the resort, while sandy beaches in front of the resort were formed and expanded widely.
Proceedings ArticleDOI
01 Mar 2003
TL;DR: Pattiara et al. as discussed by the authors investigated the applicability of conventional equations to predict littoral drift rates on a site characterised by steep beach morphology, low-wave energy conditions and a bi-modal wave climate.
Abstract: The coastline of Perth, Western Australia, is subject to one of the strongest and most consistent sea breeze systems in the world. A significant feature of the sea breeze is that it blows obliquely-onshore and has a major impact on the incident wave climate and ensuing longshore sediment transport. Reviews of field data on longshore sediment transport have concluded that there are large uncertainties regarding the behaviour on low-wave energy, steep beaches. This study investigates the applicability of conventional equations to predict littoral drift rates on a site characterised by steep beach morphology, low-wave energy conditions and a bi-modal wave climate. Littoral drift rates were measured during an impoundment study, which involved monitoring the longshore transport rate by blocking sand movement with a permanent shorenormal groyne. Weekly surveys were conducted during a five-month period and these successive surveys provide data on changes in beach morphology and volume. The results are compared with three different predictions based on wave data and littoral drift equations (CERC and Inman and Bagnold (1963) equations). The longshore sediment transport is predicted well using the CERC equation when only considering the contribution of the wind waves. The sea breeze generated littoral drift is estimated 40,000–60,000 m. This investigation confirms that the sea breeze system plays and important role in determining the sediment budget in the region. INTRODUCTION The beaches along the coastline of Perth, Western Australia, are characterised by a steep gradient (5–6 ) and are subjected to low-wave energy conditions. The coastline is 1 Graduate Student, Geography Department, Loughborough University, Loughborough, LE11 3TU, UK. A.M.Tonk@lboro.ac.uk 2 Senior Lecturer, Geography Department, Loughborough University, Loughborough, LE11 3TU, UK. G.Masselink@lboro.ac.uk 3 Associate Professor, Centre for Water Research, University of Western Australia, Nedlands, WA 6907, Australia. Pattiara@cwr.uwa.edu.au
DOI
01 Jan 2011
TL;DR: In this article, the authors apply a two-dimensional depth-averaged model, taking an horizontal large eddy simulation(HLES), to the bed morphology computed when using HLES, as well as the associated time-scale, is similar to what has been obseved in a field case.
Abstract: As demonstrated in study for non-submerged groynes, the flow field is predominantly two-dimensional, with mainly horizontal eddies. The eddies shed form the tips of the groynes and migrate in the flow direction. These eddies have horizontal dimensions in the order of tens of meters and time-scales in the order of minutes. In the standard flow simulations, these motions are usually not resolved, due to a too coarse grid, too large time steps and, more importantly, the use of inadequate turbulence modelling. using for example a k- model, it is necessary to introduce substantial modifications. Therefore simulation resolved in this study, were carried out using the DELFT-3D-MOR programme, which is part of the DELFT3D software package of WL/Delft Hydraulics and In this study, apply a two-dimensional depth-averaged model, taking an horizontal large eddy simulation(HLES). The bed morphology computed when using HLES, as well as the associated time-scale, is similar to what has been obseved in a field case. When using a mean-flow model with-out HELS, the bed morphology is less realistic and the morphological time-scale is much larger. This slow development is the result of neglecting(or averaging). the strong velocity fluctuations associated with the time-varying eddy formation.

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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202114
202020
201924
201823
201714
201617