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.

Calculation method for interaction of waves and arc-shaped plate type groyne

Abstract: The invention provides a calculation method for interaction of waves and an arc-shaped plate type groyne. According to the method, pressure-implicit with splitting of operators (PISO algorithm) is implemented, a prediction step and two modification steps are carried out, pressure is adjusted through iteration, then an internal fluid unit meets continuous equations, a free surface unit meets free surface power boundary conditions, and meanwhile a speed field is adjusted; compared with a conventional calculation method for interaction of the waves and the arc-shaped plate type groyne, the calculation method has the advantages that the calculation efficiency is high and value results are relatively approximate to physical practice since a speed field is modified by using the PISO algorithm, variable information is arranged based on alternative grids, and interaction of the waves and the arc-shaped plate type groyne is simulated by using a virtual boundary force method through central difference method discrete control equations.

Detecting the chaotic nature of advection in complex river flows

Abstract: In order to detect signatures of chaotic advection in river surface motion, surface buoys equipped with GPS were deployed in a field experiment in River Danube, Hungary. The buoys were released in the vicinity of groynes where complex mixing processes occur. A detailed analysis of the trajectories was carried out, focusing on the time evolution of the distance between buoy pairs. The analysis included the determination and comparison of local Lyapunov exponents and prediction times of finite-time hyperbolic behaviour, which is related to strong mixing. Despite of the small number of applied buoys we found evidence on Lagrangian chaos in the wake of a groyne field. In order to supplement the field data obtained by this, inherently Lagrangian, approach, experiments in a small-scale laboratory model were also carried out, in which the Lagrangian surface dynamics was detected by following the motion of numerous floaters using particle tracking velocimetry (PTV).

Spatio-temporal patterns of macrobenthic invertebrates in a free-flowing section of the River Danube in Austria

Abstract: Macrobenthic invertebrates were sampled quantitatively in the main channel of the Austrian Danube on 6 dates between April 1993 and February 1995. A modified air lift sampler (PEHOFER 1998; BRETSCHKO & SCHONBAUER 1998) was used. Due to flood control structures built during the last century, the stretch of the Danube investigated is severely regulated and characterized by straightening, steep and heavily stabilized banks, high current speeds up to 3m s -1 , and a water depth of up to 6 m with gravel sediments, Biologically important structures are restricted to a periodically inundated gravel bar and permanently inundated groyne fields. Three transects of the main channel were sampled in the centre, near the banks and near the groyne fields. Additionally, samples were also taken from areas between the groynes. Out of a total number of 181 reported taxa, only 6 species (Jaera istri, Stylodrilus heringianus, Canthocamptus staphylinus, Corophium curvispinum, Rheotanytarsus rhenanus and Rheotanytarsus sp.) were quantitatively important. Although insects were the most diverse group, with 109 out of 181 identified species so far, the most abundant groups with regard to their mean densities were Crustacea (Isopoda, Harpacticoida and Amphipoda) and worms (Oligochaeta and Nematoda) representing over 86% of the sampled fauna. The dominant taxonomic units occurred over the entire cross section. Macroinvertebrate densities were surprisingly high, even in the shipping channel with the highest current speeds and greatest water depths, but stream fauna was more abundant and diverse in areas protected from the current, such as the groyne fields. The preference of the fauma for protected areas and the distinct temporal pattern, with highest densities in summer and lowest densities in winter, was independent of the discharge regime and is attributed to the life histories of the most frequent taxa.

The Design and Application of Permeable Groynes

Abstract: Permeable groyne is an innovative type of traditional groynes, Netherlands have accumulated some experiences on this field during the practice on the Rhine and Jamuna river (Bangladesh). This paper summarized the present study results of permeable groynes and inspired by it, proposed an supplementary alternative for the river training work in the Lower Yellow River.

Mathematical model of groynes on shingle beaches

Abstract: This report describes the development of a mathematical model of a shingle beach with groynes. The development of the beach plan shape is calculated given information on its initial position and information on wave conditions just offshore. Different groyne profiles and spacings can be specified, so that alternative groyne systems can be investigated. The model includes a method for dealing with varying water levels as the result of tidal rise and fall.