scholarly journals Wave Overtopping of Stepped Revetments

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 1035 ◽  
Author(s):  
Nils B. Kerpen ◽  
Talia Schoonees ◽  
Torsten Schlurmann
Keyword(s):  
Scale Effects ◽  
Vertical Wall ◽  
Breaking Waves ◽  
Design Guidelines ◽  
Coastal Protection ◽  
Wave Overtopping ◽  
Wide Range ◽  
Run Up ◽  
The One ◽  
Parameter Ranges

Wave overtopping—i.e., excess of water over the crest of a coastal protection infrastructure due to wave run-up—of a smooth slope can be reduced by introducing slope roughness. A stepped revetment ideally constitutes a slope with uniform roughness and can reduce overtopping volumes of breaking waves up to 60% compared to a smooth slope. The effectiveness of the overtopping reduction decreases with increasing Iribarren number. However, to date a unique approach applicable for a wide range of boundary conditions is still missing. The present paper: (i) critically reviews and analyzes previous findings; (ii) contributes new results from extensive model tests addressing present knowledge gaps; and (iii) proposes a novel empirical formulation for robust prediction of wave overtopping of stepped revetments for breaking and non-breaking waves. The developed approach contrasts a critical assessment based on parameter ranges disclosed beforehand between a smooth slope on the one hand and a plain vertical wall on the other. The derived roughness reduction coefficient is developed and adjusted for a direct incorporation into the present design guidelines. Underlying uncertainties due to scatter of the results are addressed and quantified. Scale effects are highlighted.

Numerical Simulation of Wave Overtopping Based on DualSPHysics

2013 ◽  
Vol 405-408 ◽  
pp. 1463-1471 ◽  
Author(s):  
Xing Ye Ni ◽  
Wei Bin Feng
Keyword(s):  
Numerical Simulation ◽  
Vertical Wall ◽  
Breaking Waves ◽  
Numerical Wave Tank ◽  
Regular Wave ◽  
Average Deviation ◽  
Wave Overtopping ◽  
Different Types ◽  
Numerical Wave ◽  
Run Up

To obtain a more detailed description of wave overtopping, a 2-D numerical wave tank is presented based on an open-source SPH platform named DualSPHysics, using a source generation and absorption technology suited for SPH methods with analytical relaxation approach. Numerical simulation of regular wave run-up and overtopping on typical sloping dikes is carried out and satisfactory agreements are shown between numerical results and experimental data. Another overtopping simulation of regular wave is conducted against six different types of seawalls (vertical wall, curved wall, recurved wall, 1:3 slope with smooth face, 1:1.5 slope with smooth face and 1:1.5 slope with stepped-face), which represents the details of various breaking waves interacting with different seawalls, and the average deviation of wave overtopping rate is 6.8%.

A new model of shoaling and breaking waves. Part 2. Run-up and two-dimensional waves

2019 ◽  
Vol 867 ◽  
pp. 146-194 ◽  
Author(s):  
G. L. Richard ◽  
A. Duran ◽  
B. Fabrèges
Keyword(s):  
Large Scale ◽  
Turbulent Viscosity ◽  
Breaking Waves ◽  
Small Scale ◽  
Two Dimensional ◽  
Numerical Resolution ◽  
Wide Range ◽  
Scale Turbulence ◽  
Run Up ◽  
Averaged Model

We derive a two-dimensional depth-averaged model for coastal waves with both dispersive and dissipative effects. A tensor quantity called enstrophy models the subdepth large-scale turbulence, including its anisotropic character, and is a source of vorticity of the average flow. The small-scale turbulence is modelled through a turbulent-viscosity hypothesis. This fully nonlinear model has equivalent dispersive properties to the Green–Naghdi equations and is treated, both for the optimization of these properties and for the numerical resolution, with the same techniques which are used for the Green–Naghdi system. The model equations are solved with a discontinuous Galerkin discretization based on a decoupling between the hyperbolic and non-hydrostatic parts of the system. The predictions of the model are compared to experimental data in a wide range of physical conditions. Simulations were run in one-dimensional and two-dimensional cases, including run-up and run-down on beaches, non-trivial topographies, wave trains over a bar or propagation around an island or a reef. A very good agreement is reached in every cases, validating the predictive empirical laws for the parameters of the model. These comparisons confirm the efficiency of the present strategy, highlighting the enstrophy as a robust and reliable tool to describe wave breaking even in a two-dimensional context. Compared with existing depth-averaged models, this approach is numerically robust and adds more physical effects without significant increase in numerical complexity.

scholarly journals Numerical Modeling of Failure Mechanisms in Articulated Concrete Block Mattress as a Sustainable Coastal Protection Structure

2021 ◽  
Vol 13 (22) ◽  
pp. 12794
Author(s):  
Ramin Safari Ghaleh ◽  
Omid Aminoroayaie Yamini ◽  
S. Hooman Mousavi ◽  
Mohammad Reza Kavianpour
Keyword(s):  
Numerical Modeling ◽  
Concrete Block ◽  
Breaking Waves ◽  
Physical Models ◽  
Coastal Protection ◽  
Similarity Parameter ◽  
Environmental Friendliness ◽  
Shoreline Protection ◽  
Concrete Blocks ◽  
Run Up

Shoreline protection remains a global priority. Typically, coastal areas are protected by armoring them with hard, non-native, and non-sustainable materials such as limestone. To increase the execution speed and environmental friendliness and reduce the weight of individual concrete blocks and reinforcements, concrete blocks can be designed and implemented as Articulated Concrete Block Mattress (ACB Mat). These structures act as an integral part and can be used as a revetment on the breakwater body or shoreline protection. Physical models are one of the key tools for estimating and investigating the phenomena in coastal structures. However, it does have limitations and obstacles; consequently, in this study, numerical modeling of waves on these structures has been utilized to simulate wave propagation on the breakwater, via Flow-3D software with VOF. Among the factors affecting the instability of ACB Mat are breaking waves as well as the shaking of the revetment and the displacement of the armor due to the uplift force resulting from the failure. The most important purpose of the present study is to investigate the ability of numerical Flow-3D model to simulate hydrodynamic parameters in coastal revetment. The run-up values of the waves on the concrete block armoring will multiply with increasing break parameter (0.5<ξm−1,0<3.3) due to the existence of plunging waves until it (Ru2%Hm0=1.6) reaches maximum. Hence, by increasing the breaker parameter and changing breaking waves (ξm−1,0>3.3) type to collapsing waves/surging waves, the trend of relative wave run-up changes on concrete block revetment increases gradually. By increasing the breaker index (surf similarity parameter) in the case of plunging waves (0.5<ξm−1,0<3.3), the low values on the relative wave run-down are greatly reduced. Additionally, in the transition region, the change of breaking waves from plunging waves to collapsing/surging (3.3<ξm−1,0<5.0), the relative run-down process occurs with less intensity.

scholarly journals EXPERIMENTAL STUDY ON THE OVERTOPPING BEHAVIOUR OF STEEP SLOPES – TRANSITION BETWEEN MILD SLOPES AND VERTICAL WALLS

2012 ◽  
Vol 1 (33) ◽  
pp. 61
Author(s):  
Lander Victor ◽  
Peter Troch
Keyword(s):  
Slope Angle ◽  
Breaking Waves ◽  
The Other ◽  
Prediction Methods ◽  
Wave Overtopping ◽  
Wave Energy Converters ◽  
Vertical Walls ◽  
The One ◽  
Steep Slopes ◽  
Existing Data

Extensive knowledge is available on the overtopping behaviour of traditional smooth impermeable sea defence structures, such as mildly sloping dikes and vertical walls, both typically featuring a high crest freeboard to reduce wave overtopping. A particular design application emerges in the development of wave energy converters of the overtopping type, where maximisation of wave overtopping is required, i.e. smooth impermeable steep sloping structures with low crest freeboards subjected to non-breaking waves. To date, only relatively limited knowledge is available on the overtopping behaviour of those structures. In this study, the average overtopping rate obtained from new experiments has been analysed and compared with existing prediction methods. This study contributes to a better knowledge on the overtopping behaviour of the steep low-crested structures, which is positioned in between that of mildly sloping dikes and vertical walls on the one hand, and in between that of structures with zero crest freeboards and relatively large crest freeboards on the other hand. The existing prediction methods seem unable to predict the significant effects of the slope angle and small relative crest freeboards on the average overtopping rate accurately. Therefore, a new set of prediction formulae is proposed based on the new experiments combined with existing data from literature. These formulae include wave overtopping at vertical walls subjected to non-impacting waves and at structures with zero crest freeboard.

scholarly journals REDUCTION ON WAVE OVERTOPPING ON A SMOOTH DIKE BY MEANS OF A PARAPET

2011 ◽  
Vol 1 (32) ◽  
pp. 6 ◽  
Author(s):  
Koen Van Doorslaer ◽  
Julien De Rouck
Keyword(s):  
Vertical Wall ◽  
Breaking Waves ◽  
Wave Overtopping ◽  
Optimal Geometry ◽  
Efficient Construction ◽  
Major Reduction ◽  
Crest Height ◽  
Reduction Factors

A return wall or parapet is a very efficient construction built to reduce wave overtopping over sea structures. One of its main advantages is that this relative small construction can be built in a dike without increasing the crest height yet creating a major reduction in wave overtopping. In this paper only non-breaking waves attacking smooth dikes are investigated. A normal smooth dike, a smooth dike with vertical wall and a smooth dike with parapet have been tested. The results lead to reduction factors for a vertical wall or a parapet that can be introduced in the van der Meer formulas for wave overtopping over smooth dikes. The optimal geometry of the parapet has been subject of the research as well.

Reasons and ways to manipulate financial statements

2020 ◽  
Vol 19 (6) ◽  
pp. 1121-1132 ◽  
Author(s):  
Ya.P. Fedorov
Keyword(s):  
Financial Reporting ◽  
Systems Approach ◽  
Operating Cost ◽  
Financial Statements ◽  
Financial Accounting ◽  
Cost Category ◽  
Wide Range ◽  
Analysis And Synthesis ◽  
Run Up ◽  
The One

Subject. The article considers the reasons and tools for manipulation of financial statements and ways to identify it. Objectives. The purpose of the study is to reveal preconditions and the main instruments of misstatements of financial reporting. Methods. The study employs empirical and logical constructions, analysis and synthesis, generalization, systems approach, methods of comparative analysis. Results. I show the main ways of misstatements of financial reporting and formulate mechanisms to detect them. The findings can be useful for enhancing the financial accounting standards, as well as for all interested stakeholders of enterprises that use financial statements. Conclusions. The absence of adequate responsibility of auditors and appraisers involved in the preparation and confirmation of reporting contributes to the practice of misrepresentation of financial statements. On the one hand, a company hires appraisers or auditors and pays for their services, and the latter have no motivation to engage in any confrontation with the company that manipulates its financial statements. On the other hand, companies, pursuing various goals (meeting the KPIs by managers or in the run-up to the M&A transaction), apply window dressing and manipulate their financial statements, using a wide range of tools, like revenues reposting, provisions for impairment, reclassification of costs from the operating cost to capital cost category, etc.

Extreme run-up events on a vertical wall due to nonlinear evolution of incident wave groups

2016 ◽  
Vol 797 ◽  
pp. 644-664 ◽  
Author(s):  
Gal Akrish ◽  
Oded Rabinovitch ◽  
Yehuda Agnon
Keyword(s):  
Nonlinear Wave ◽  
Deep Water ◽  
Incident Wave ◽  
Water Waves ◽  
Nonlinear Evolution ◽  
Vertical Wall ◽  
Computational Domain ◽  
Wave Groups ◽  
Wide Range ◽  
Run Up

Nonlinear evolution of long-crested wave groups can lead to extreme interactions with coastal and marine structures. In the present study the role of nonlinear evolution in the formation of extreme run-up events on a vertical wall is investigated. To this end, the fundamental problem of interaction between non-breaking water waves and a vertical wall over constant water depth is considered. In order to simulate nonlinear wave–wall interactions, the high-order spectral method is applied to a computational domain which aims to represent a two-dimensional wave flume. Wave generation is simulated at the flume entrance by means of the additional potential concept. Through this concept, the implementation of a numerical wavemaker is applicable. In addition to computational efficiency, the adopted numerical approach enables one to consider the evolution of nonlinear waves while preserving full dispersivity. Utilizing these properties, the influence of the nonlinear wave evolution on the wave run-up can be examined for a wide range of water depths. In shallow water, it is known that nonlinear evolution of incident waves may result in extreme run-up events due to the formation of an undular bore. The present study reveals the influence of the nonlinear evolution on the wave run-up in deep-water conditions. The results suggest that extreme run-up events in deep water may occur as a result of the disintegration of incident wave groups into envelope solitons.

scholarly journals WAVE OVERTOPPING AT DYKES WITH TOPPED VERTICAL WALL - IMPACTS OF OBLIQUE WAVE ATTACK

2012 ◽  
Vol 1 (33) ◽  
pp. 60
Author(s):  
Nils B. Kerpen ◽  
Torsten Schlurmann
Keyword(s):  
Numerical Models ◽  
Vertical Wall ◽  
Coastal Protection ◽  
Wave Spectra ◽  
Wave Overtopping ◽  
Oblique Wave ◽  
Wave Basin ◽  
Vertical Walls ◽  
The Mean ◽  
Analytical Approaches

Hydraulic model tests at a scale of 1:10 are carried out in a 40 m x 25 m wave basin with a state-of-the-art 3D wave generator in order to collect wave overtopping data at vertical walls and dykes with topped vertical walls. Wave conditions in the near field of the structures, velocities under waves and the mean overtopping discharge are measured. The experiments have been commissioned by the Lower Saxony Water Management, Coastal Defense and Nature Conservation Agency (NLWKN) with the purpose to deliver essential overtopping data for validation of numerical models. Two main geometries are analyzed – each for two specific wave spectra. Overtopping rates are investigated with respect to the remaining freeboard height Rc and the influence of oblique wave attack β{0°, 10°, 30°, 40°, 50°, 60°}. Results are compared with existing analytical approaches. As expected for this special geometrical coastal protection structure, it is examined that overtopping discharges increase with decreasing remaining freeboard. Intensity of the reduction is more dependent on the wave spectra than on the dyke geometry. Mean wave overtopping rate increases with decreasing relative water depth Hm0/d directly in front of the vertical wall. Furthermore, the mean wave overtopping rates decrease with an increasing angle of wave attack β. The correlation between mean wave overtopping rate and freeboard height is given in four newly adapted design formulas, describing the overtopping performance of the two discussed dyke geometries with topped vertical walls.

scholarly journals OVERFLOW AND WAVE OVERTOPPING OVER BROAD QUAY WALLS MODELED WITH OPENFOAM

2018 ◽  
pp. 19
Author(s):  
Dieter Vanneste ◽  
Wim Van Hoydonck ◽  
Daphné Thoon
Keyword(s):  
Storm Surges ◽  
Breaking Waves ◽  
Failure Behavior ◽  
Front Edge ◽  
Wave Overtopping ◽  
The North ◽  
The North Sea ◽  
Run Up ◽  
The Eu

In the framework of the EU Floods Directive, Flanders Hydraulics Research (FHR) is performing flood modeling studies to evaluate the flood risk along the Belgian coast due to extreme storm surges on the North Sea. Thereto, amongst others, the failure behavior of quay walls in the coastal ports must be determined. Computing the landward non-impulsive wave overtopping discharge over a broad quay, in some cases combined with overflow, on which a flood wall can be present at large distance [O (100 m)] from the front edge poses a particular challenge. This matter, to the authors’ knowledge, is not covered in existing literature, e.g. the European Overtopping Manual. It is also not possible to apply the method for reduction of wave overtopping over a wide crest according to Verwaest et al. (2010), since it was developed for breaking waves on a shallow foreshore overtopping a sloping dike, requiring the determination of a run-up level. It is clear that the landward water flow on the quay should be investigated in more detail, as it is characterized by bottom friction and possible inertia due interaction with the flow reflected at the flood wall. To this end, the CFD toolbox OpenFOAM is used to model the final discharges at the landward side of the quay.

A laboratory study of suspension-effect density currents

1969 ◽  
Vol 6 (2) ◽  
pp. 231-246 ◽  
Author(s):  
John F. Riddell
Keyword(s):  
Laboratory Tests ◽  
Settling Velocity ◽  
Scale Effects ◽  
Density Currents ◽  
Material Particle ◽  
Exchange Method ◽  
Wide Range ◽  
Suspension Effect ◽  
The One ◽  
Expected Increase

Suspension-effect density currents formed by both natural and non-natural materials have been investigated in three series of laboratory tests. The lock exchange method of current formation has been shown to be unsuitable for suspensions of high settling velocity and a more effective, dropping method of release has been devised. The adoption of a new linear proportionality equation for correctly correlating the variables acting on the system has demonstrated the significance of the densimetric Froude-Reynolds number for suspension-effect current studies.Quantitative plots of extension against time and non-dimensional time have been prepared for a wide range of concentrations of different materials and the expected increase in both velocity and total extension with increasing concentration verified. For suspensions of constant initial concentration, increase in material particle size has been shown to result in underflows of increased velocity but reduced extension. Mixtures of coarse and fine material in the one suspension have also been investigated.Viscous scale effects have been examined by using two sizes of geometically similar flumes and a short range congruency type of diagram prepared for suspensions of a natural river sediment.Suspension effect currents are compared with the simpler solution effect currents and the greater influence of viscosity on the former discussed together with the suitability of using solution current congruency diagrams for model/prototype studies of suspension-effect currents.

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