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1
Gu, Jiayue, Xin Hu, Shuguang Liu und Quanhe Ju. „INFLUENCE OF CROWN-WALL ON WAVE OVERTOPPING PROBABILITY AND PROBABILITY DISTRIBUTION OVER A SEAWALL“. Coastal Engineering Proceedings, Nr. 36 (30.12.2018): 70. http://dx.doi.org/10.9753/icce.v36.structures.70.
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In the past decades, the crest height of the seawall was determined by the allowable average wave overtopping rate q. Franco (1994) concluded that individual wave overtopping，particularly the maximum individual volume, provided a better design method than q, considering the stability of the seawall and the safety of vehicles and people along the coastal area protected by the coastal defense structures. Shanghai, located on the west bank of the Pacific Ocean, is quite sensitive to the risk of storm surges and violent wave overtopping. The crown-wall serves as an engineering measure to reduce the wave overtopping effectively.
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Van der Meer, Jentsje Wouter, Bianca Hardeman, Gosse Jan Steendam, Holger Schuttrumpf und Henk Verheij. „FLOW DEPTHS AND VELOCITIES AT CREST AND LANDWARD SLOPE OF A DIKE, IN THEORY AND WITH THE WAVE OVERTOPPING SIMULATOR“. Coastal Engineering Proceedings 1, Nr. 32 (31.01.2011): 10. http://dx.doi.org/10.9753/icce.v32.structures.10.
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Wave overtopping discharges at coastal structures are well described in the EurOtop Manual (2007), including the distribution of overtopping wave volumes. Each volume that overtops a dike or levee will have a certain flow velocity and depth record in time, often given by the maximum velocity and flow depth. This paper describes some further development of the theory on flow depth and velocities on the crest, but will also show an inconsistency with respect to the mass balance. The second part of the paper gives an analysis of measured values on real dikes, simulated by the Wave Overtopping Simulator. It gives also the method of "cumulative hydraulic load" to compare overtopping discharges for different wave conditions. A large wave height with less overtopping waves, but larger overtopping wave volumes, is more damaging than a small wave height with more, but smaller overtopping volumes, even if the overtopping discharge is similar. The reasons to develop the cumulative hydraulic load have been compared with the recently in the US developed method of erosional equivalence.
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Altomare, Corrado, Xavi Gironella, Tomohiro Suzuki, Toon Verwaest, Mauro Campagnola und Alessandra Saponieri. „OVERTOPPING FLOWS AND RELATED HAZARDS: A CASE OF STUDY FROM THE CATALAN COAST“. Coastal Engineering Proceedings, Nr. 36v (28.12.2020): 10. http://dx.doi.org/10.9753/icce.v36v.structures.10.
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Design criteria for coastal defenses exposed to wave overtopping are usually restricted to the assessment of mean discharges and maximum individual overtopping volumes, however it is not possible to give unambiguous or precise limits to tolerable overtopping for all kind of layouts (EurOtop, 2018). A few studies (e.g. Endoh and Takahashi, 1994) analyzed the relationship between wave overtopping flows and hazard levels for people at the crest of sea dikes. Sandoval (2016) confirmed that one single value of admissible mean discharge or individual overtopping volume is not a sufficient indicator of the hazard, but detailed characterization of flow velocities and depths is required. This work presents the results of an experimental campaign aiming at characterizing the flow characteristics associated to maximum individual overtopping volumes for an urbanized stretch of a town along the Catalan coast, where a bike path and a railway run along the coastline, exposed to significant overtopping events every stormy season.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/DwVl9wFJoq0
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Altomare, Corrado, Xavi Gironella, Tomohiro Suzuki, Giacomo Viccione und Alessandra Saponieri. „Overtopping Metrics and Coastal Safety: A Case of Study from the Catalan Coast“. Journal of Marine Science and Engineering 8, Nr. 8 (24.07.2020): 556. http://dx.doi.org/10.3390/jmse8080556.
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Design criteria for coastal defenses exposed to wave overtopping are usually assessed by mean overtopping discharges and maximum individual overtopping volumes. However, it is often difficult to give clear and precise limits of tolerable overtopping for all kinds of layouts. A few studies analyzed the relationship between wave overtopping flows and hazard levels for people on sea dikes, confirming that one single value of admissible mean discharge or individual overtopping volume is not a sufficient indicator of the hazard, but detailed characterization of flow velocities and depths is required. This work presents the results of an experimental campaign aiming at analyzing the validity of the safety limits and design criteria for overtopping discharge applied to an urbanized stretch of the Catalan coast, exposed to significant overtopping events every stormy season. The work compares different safety criteria for pedestrians. The results prove that the safety of pedestrians on a sea dike can be still guaranteed, even for overtopping volumes larger than 1,000 L/m. Sea storms characterized by deep-water wave height between 3.6 and 4.5 m lead to overtopping flow depth values larger than 1 m and flow velocities up to 20 m/s. However, pedestrian hazard is proved to be linked to the combination of overtopping flow velocity and flow depth rather than to single maximum values of one of these parameters. The use of stability curves to assess people’s stability under overtopping waves is therefore advised.
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Tessema, Netsanet Nigatu, Fjóla G. Sigtryggsdóttir, Leif Lia und Asie Kemal Jabir. „Case Study of Dam Overtopping from Waves Generated by Landslides Impinging Perpendicular to a Reservoir’s Longitudinal Axis“. Journal of Marine Science and Engineering 7, Nr. 7 (15.07.2019): 221. http://dx.doi.org/10.3390/jmse7070221.
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Landslide-generated impulse waves in dammed reservoirs run up the reservoir banks as well as the upstream dam slope. If large enough, the waves may overtop and even breach the dam and cause flooding of the downstream area with hazardous consequences. Hence, for reservoirs in landslide-prone areas, it is important to provide a means to estimate the potential size of an event triggered by landslides along the reservoir banks. This research deals with landslide-generated waves and the overtopping process over the dam crest in a three-dimensional (3D) physical model test, presenting a case study. The model set-up describes the landslide impacting the reservoir in a perpendicular manner, which is often the case in natural settings. Based on the experimental results, dimensionless empirical relations are derived between the overtopping volume and the governing parameters, namely the slide volume, slide release height, slide impact velocity, still-water depth, and upstream dam face slope. Predictive relations for the overtopping volume are presented as applicable for cases relating to the specific model set-up. Measured overtopping volumes are further compared to a two-dimensional (2D) case reported in the literature. An important feature regarding the overtopping process for the 3D case is the variation in time and space, resulting in an uneven distribution of the volume of water overtopping the dam crest. This observation is made possible by the 3D model set-up, and is of value for dam safety considerations as well as for foundation-related issues, including erosion and scouring.
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Cole, E. C., M. Newton und A. Youngblood. „Effects of overtopping on growth of white spruce in Alaska“. Canadian Journal of Forest Research 43, Nr. 9 (September 2013): 861–71. http://dx.doi.org/10.1139/cjfr-2013-0117.
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Early establishment of competing vegetation often presents an obstacle to the success of planted white spruce (Picea glauca (Moench) Voss) seedlings. We followed growth and development of white spruce and associated vegetation for up to 17 years in Alaska’s boreal forests to quantify roles of overtopping plant cover in suppressing conifers. The three study areas represented a range of site conditions of varying productivity and species of competing cover, different site preparation and release treatments, and different bare-root and container white spruce stock types. Herbaceous overtopping peaked early after planting and decreased as white spruce were able to outgrow competitors. Overtopping by shrubs and hardwoods, especially aspen (Populus tremuloides Michx.) and resin birch (Betula neoalaskana Sarg.) peaked somewhat later than herbaceous overtopping and decreased over time for most sites and treatments. In a model that combined all sites, vegetation management treatments, and years, overtopping and previous year’s volume explained approximately 85% of the variation in volume growth. Increasing the size of planting stock helped reduce overtopping, hence suppression, even in treatments dominated by hardwood species. Results suggested that control of overtopping was essential for maximum growth and long-term or increasing levels of overtopping severely suppressed white spruce seedling growth.
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HOGG, ANDREW J., TOM E. BALDOCK und DAVID PRITCHARD. „Overtopping a truncated planar beach“. Journal of Fluid Mechanics 666 (16.11.2010): 521–53. http://dx.doi.org/10.1017/s0022112010004325.
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Run-up on a truncated impermeable beach is analysed theoretically and experimentally to find the volume of fluid, associated with a single wave event, that flows over the end of the beach. The theoretical calculations investigate the motion using the shallow-water equations and the fluid is allowed to flow freely over the end of the beach. Two models of wave events are considered: dam-break initial conditions, in which fluid collapses from rest to run-up and overtop the beach, and a waveform that models swash associated with the collapse of a long solitary bore. The calculations are made using quasi-analytical techniques, following the hodograph transformation of the governing equations. They yield predictions for the volume of fluid per unit width that overtops the beach, primarily as a function of the dimensionless length of the beach. These predictions are often far in excess of previous theoretical calculations. New experimental results are also reported in which the overtopping volumes due to flows initiated from dam-break conditions are studied for a range of reservoir lengths and heights and for a range of lengths and inclinations of the beach. Without the need for any empirically fitted parameters, good agreement is found between the experimental measurements and the theoretical predictions in regimes for which the effects of drag are negligible.
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Tessema, Netsanet, Fjóla Sigtryggsdóttir, Leif Lia und Asie Jabir. „Physical Model Study on Discharge over a Dam Due to Landslide Generated Waves“. Water 12, Nr. 1 (15.01.2020): 234. http://dx.doi.org/10.3390/w12010234.
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Impulse waves generated by landslides falling into reservoirs may lead to overtopping of a dam and, in turn, to flooding of the downstream area. In the case of an embankment dam, the overtopping may lead to erosion of the downstream slope, ultimately resulting in breaching and complete failure with consequent further hazardous release of water to the downstream area. This research deals with the overtopping process of a dam due to landslide generated waves in a three-dimensional (3D) physical scale model setup. Experiments have been conducted with varying the slide, reservoir, and dam parameters. The primary focus is on investigating the feasibility of employing the steady state weir equation in order to predict the overtopping discharge over a dam crest due to landslide generated waves. Calibration and validation of the coefficient of discharge values for the different dam section are conducted for the specified model setup. Accordingly, a two-step calculation procedure is presented for predicting the overtopping discharge based on the maximum overtopping depth values. Hence, for the fixed setup, which includes a constant slope angle of the landslide surface, a predictive equation for maximum overtopping depth is proposed, based on slide volume, slide release height, still water depth, upstream dam slope angle, and dam height. The relative slide volume and relative still water depth both seem to have a significant effect on the relative overtopping depth.
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Iuppa, Claudio, Luca Cavallaro, Rosaria Ester Musumeci, Diego Vicinanza und Enrico Foti. „Empirical overtopping volume statistics at an OBREC“. Coastal Engineering 152 (Oktober 2019): 103524. http://dx.doi.org/10.1016/j.coastaleng.2019.103524.
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Baldock, T. E., D. Peiris und A. J. Hogg. „Overtopping of solitary waves and solitary bores on a plane beach“. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 468, Nr. 2147 (18.07.2012): 3494–516. http://dx.doi.org/10.1098/rspa.2011.0729.
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The overtopping of solitary waves and bores present major hazards during the initial phase of tsunami inundation and storm surges. This paper presents new laboratory data on overtopping events by both solitary waves and solitary bores. Existing empirical overtopping scaling laws are found to be deficient for these wave forms. Two distinct scaling regimes are instead identified. For solitary waves, the overtopping rates scale linearly with the deficit in run-up freeboard. The volume flux in the incident solitary wave is also an important parameter, and a weak dependence on the nonlinearity of the waves ( H / d ) is observed. For solitary bores, the overtopping cannot be scaled uniquely, because the fluid momentum behind the incident bore front is independent of the bore height, but it is in close agreement with recent solutions of the nonlinear shallow water equations. The maximum overtopping rate for the solitary waves is shown to be the lower bound of the overtopping rate for the solitary bores with the same deficit in freeboard. Thus, for a given run-up, the solitary bores induce greater overtopping rates than the solitary waves when the relative freeboard is small.
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Llana, Alberto, Rafael Molina, Alberto Camarero, Alvaro Campos, Ana Francisca Alises und José Damián López. „OVERTOPPING FLOW PROPERTIES CHARACTERIZATION IN LABORATORY AND PROTOTYPE THROUGH THE COMBINATION OF NON INTRUSIVE INSTRUMENTAL TECHNIQUES“. Coastal Engineering Proceedings 1, Nr. 33 (15.12.2012): 46. http://dx.doi.org/10.9753/icce.v33.currents.46.
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Overtopping events may cause different failure modes depending on overtopped flow characteristics. Most of the studies about overtopping hazard analysis link the damages caused by the overtopping event to its mean overtopping discharge (q), which provides no information about overtopped flow characteristics or its spatial distribution. In this paper it is presented a non intrusive measurement system based on video imagery techniques and optical level sensors (OLS), which aim is to obtain overtopped highly aerated flows´ principal characteristics: velocity, volume, and density, in order to deep in the knowledge of this phenomenon, and minimizing the damages that it may cause to port´s infrastructures and exploitation
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Requena, A. I., L. Mediero und L. Garrote. „A bivariate return period based on copulas for hydrologic dam design: accounting for reservoir routing in risk estimation“. Hydrology and Earth System Sciences 17, Nr. 8 (01.08.2013): 3023–38. http://dx.doi.org/10.5194/hess-17-3023-2013.
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Abstract. A multivariate analysis on flood variables is needed to design some hydraulic structures like dams, as the complexity of the routing process in a reservoir requires a representation of the full hydrograph. In this work, a bivariate copula model was used to obtain the bivariate joint distribution of flood peak and volume, in order to know the probability of occurrence of a given inflow hydrograph. However, the risk of dam overtopping is given by the maximum water elevation reached during the routing process, which depends on the hydrograph variables, the reservoir volume and the spillway crest length. Consequently, an additional bivariate return period, the so-called routed return period, was defined in terms of risk of dam overtopping based on this maximum water elevation obtained after routing the inflow hydrographs. The theoretical return periods, which give the probability of occurrence of a hydrograph prior to accounting for the reservoir routing, were compared with the routed return period, as in both cases hydrographs with the same probability will draw a curve in the peak-volume space. The procedure was applied to the case study of the Santillana reservoir in Spain. Different reservoir volumes and spillway lengths were considered to investigate the influence of the dam and reservoir characteristics on the results. The methodology improves the estimation of the Design Flood Hydrograph and can be applied to assess the risk of dam overtopping.
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van Bergeijk, Vera M., Jord J. Warmink und Suzanne J. M. H. Hulscher. „Modelling the Wave Overtopping Flow over the Crest and the Landward Slope of Grass-Covered Flood Defences“. Journal of Marine Science and Engineering 8, Nr. 7 (02.07.2020): 489. http://dx.doi.org/10.3390/jmse8070489.
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The wave overtopping flow can exert high hydraulic loads on the grass cover of dikes leading to failure of the cover layer on the crest and the landward slope. Hydraulic variables such as the near bed velocity, pressure, shear stress and normal stress are important to describe the forces that may lead to cover erosion. This paper presents a numerical model in the open source software OpenFOAM® to simulate the overtopping flow on the grass-covered crest and slope of individual overtopping waves for a range of landward slope angles. The model provides insights on how the hydraulic forces change along the profile and how irregularities in the profile affect these forces. The effect of irregularities in the grass cover on the overtopping flow are captured in the Nikuradse roughness height calibrated in this study. The model was validated with two datasets of overtopping tests on existing grass-covered dikes in the Netherlands. The model results show good agreement with measurements of the flow velocity in the top layer of the wave, as well as the near bed velocity. The model application shows that the pressure, shear stress and normal stress are maximal at the wave front. High pressures occur at geometrical transitions such as the start and end of the dike crest and at the inner toe. The shear stress is maximal on the lower slope, and the normal stress is maximal halfway of the slope, making these locations vulnerable to cover failure due to high loads. The exact location of the maximum forces depends on the overtopping volume. Furthermore, the model shows that the maximum pressure and maximum normal stress are largely affected by the steepness of the landward slope, but the slope steepness only has a small effect on the maximum flow velocity and maximum shear stress compared to the overtopping volume. This new numerical model is a useful tool to determine the hydraulic forces along the profile to find vulnerable points for cover failure and improve the design of grass-covered flood defences.
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PEREGRINE, D. H., und S. M. WILLIAMS. „Swash overtopping a truncated plane beach“. Journal of Fluid Mechanics 440 (10.08.2001): 391–99. http://dx.doi.org/10.1017/s002211200100492x.
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Swash on a plane beach is modelled by using a solution of the shallow-water equations due to Shen & Meyer (1963). The equations are used in a form appropriate for a plane at a finite angle to the horizontal. The beach is cut-off at a level below that of the maximum run-up, and the water is taken to fall freely over the end of the beach. An explicit solution is found which permits evaluation of the overtopping flow and total volume for one swash event.
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Paape, A. „EXPERIMENTAL DATA ON THE OVERTOPPING OF SEAWALLS BY WAVES“. Coastal Engineering Proceedings 1, Nr. 7 (29.01.2011): 36. http://dx.doi.org/10.9753/icce.v7.36.
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In the past it has been found that serious damage and breaching of seawalls is most frequently caused by overtopping. Hence for the design of seawalls data must be available about the overtopping by waves of the different profiles that might be possible. Naturally the conditions under which damage is caused to the seawall also depend on the type of construction and the materials used, for example: the stability of grass covered dikes can be endangered seriously by water flowing over the inner slope. In many designs the necessary height of a seawall has been defined such that not more than 2% of the waves overtop the crest, under chosen design conditions. This criterion has been determined on the assumption that the overtopping must remain very small. Some overtopping has to be accepted because no maximum value for wave height and wave run-up can be given, unless of course the wave height is limited by fore-shore conditions. Unfortunately this criterion gives no information about the volume and concentration of water overtopping the crest in each instance. Moreover it is of interest to know how this overtopping varies with other conditions, such as changes in the significant wave height. Information about the overtopping by waves was obtained from model investigations on simple plane slopes w^th inclinations varying from 1 : 8 to 1 : 2. The experiments were made in a windflume where wind generated waves as well as regular waves were employed. Using wind generated waves, conditions from nature regarding the distribution of wave heights could be reproduced. It appeared that the overtopping depends on the irregularity of the waves and that the same effects cannot be reproduced using regular paddle generated waves. In this paper a description of the model and the results of these tests are given. Investigations are m progress on composite slopes, including the reproduction of conditions for a seawall which suffered much overtopping but remained practically undamaged during the flood of 1953.
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Steendam, Gosse Jan, Jentsje Wouter Van der Meer, Andre Van Hoven und Astrid Labrujere. „WAVE RUN-UP SIMULATIONS ON REAL DIKES“. Coastal Engineering Proceedings, Nr. 35 (23.06.2017): 42. http://dx.doi.org/10.9753/icce.v35.structures.42.
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A new Wave Run-up Simulator has been designed, constructed, calibrated and used for testing of the seaward face of dikes. The upper part of dikes or levees often have a clay layer with a grass cover. The new device is able to test the strength of the grass cover under simulation of up-rushing waves for pre-defined storm conditions. The cumulative overload method has been developed to describe the strength of grass covers on the crest and landward side of dikes, for overtopping wave volumes. In essence there is not a lot of difference between the hydraulic load from an overtopping wave volume or from an up-rushing wave. Therefore the hypothesis has been evaluated that the cumulative overload method should also be applicable for up-rushing waves. Tests on a real dike have been used to validate this hypothesis. The main conclusions are that the new Wave Overtopping Simulator works really well, but that the results on testing till so far has not yet been sufficient for a full validation of the method. More research is required. Furthermore, a new technique has been developed to measure the strength of a grass sod on a dike: the grass pulling device. Tests with this device showed that it is possible to measure the critical velocity (= strength) of a grass cover, which is much easier than performing tests with a Wave Run-up or Overtopping Simulator.
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TANAKA, Hiromichi, Tomoya INAMI und Tetsuo SAKURADA. „Characteristics of Volume of Overtopping and Water Supply Quantity for Developing Wave Overtopping Type Wave Power Generation Equipment“. Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 70, Nr. 2 (2014): I_1301—I_1305. http://dx.doi.org/10.2208/kaigan.70.i_1301.
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Barbosa, D. V. E., J. A. Souza, E. D. dos Santos, L. A. Isoldi und J. C. Martins. „NUMERICAL ANALYSES OF OPENFOAM'S OVERTOPPING DEVICE SOLUTION“. Revista de Engenharia Térmica 16, Nr. 1 (30.06.2017): 96. http://dx.doi.org/10.5380/reterm.v16i1.62198.
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Studies related to ocean energy are getting more important lately, once world claims for renewable energy usage. The Overtopping Device is a kind of Ocean Waves Energy Converter (OWEC), which main concept is storing water provided by incident waves above sea level to feed a set of low head turbines. In order to obtain the desired effect, this device contains a ramp which elevates the incident waves toward the reservoir. Present study aims to perform a numerical model of a 2D Overtopping Device by means of OpenFOAM simulations. OpenFOAM is a free open source code which has shown applicability in many areas of engineering. The adopted solver (InterFOAM) is Volume of Fluid based (VOF) according to Finite Volume Method (FVM), these methodologies has been largely used among researchers in propagating waves field. FLUENT (commercial code) is used to verify OpenFOAM's results. Once, the main point of this paper is to present OpenFOAM as a considerable tool for propagating waves studies, it firstly presents a numerical wave verification with analytical solutions (second order Stokes theory). The second section of results presents overtopping time series peaks in 100 s of simulation. Also, by mass flow rate integration, it presents total mas of water climbed to the reservoir. The integration of mass flow rate takes 94 s of simulation (not 100 s) because it is noticeable a pause between two peaks of overtopping at that time. Results show agreement between wave elevation and wave velocity profiles with straight convergence of periods between analytical and numerical waves. Most important differences are found near air/water interface, owed to faster air flow at that region. Generally OpenFOAM and FLUENT results are similar, with converged overtopping time series peaks and their magnitudes too. Similarly, the amount of water marked by both software are close with very similar trend lines.
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Requena, A. I., L. Mediero und L. Garrote. „Bivariate return period based on copulas for hydrologic dam design: comparison of theoretical and empirical approach“. Hydrology and Earth System Sciences Discussions 10, Nr. 1 (15.01.2013): 557–96. http://dx.doi.org/10.5194/hessd-10-557-2013.
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Abstract. Hydrologic frequency analyses are usually focused on flood peaks. Multivariate analyses on flood variables have not been so exhaustively studied despite the fact that they are required to represent the full hydrograph, which is essential for designing some structures like dams. In this work, a bivariate copula model was used to obtain the bivariate joint distribution of flood peak and volume. An empirical bivariate return period was defined in terms of acceptable risk to the dam through the maximum water elevation reached during the routing process, in order to perform a risk assessment of dam overtopping. A Monte Carlo procedure was developed to compare the probability of occurrence of a flood with the return period linked to the risk of dam overtopping. The procedure is applied to the case study of the Santillana reservoir in Spain. A set of synthetic peak-volume pairs was generated by the fitted copula and synthetic hydrographs were routed through the reservoir. Different reservoir volumes and spillway lengths were considered. Hydrographs with the same risk were represented by a curve in the peak-volume space. These curves were compared to those linked to the probability of occurrence of a flood event, in order to improve the estimation of the Design Flood Hydrograph.
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dos Santos, Elizaldo Domingues, Bianca Neves Machado, Marcos Moisés Zanella, Mateus das Neves Gomes, Jeferson Avila Souza, Liércio André Isoldi und Luiz Alberto Oliveira Rocha. „Numerical Study of the Effect of the Relative Depth on the Overtopping Wave Energy Converters According to Constructal Design“. Defect and Diffusion Forum 348 (Januar 2014): 232–44. http://dx.doi.org/10.4028/www.scientific.net/ddf.348.232.
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The conversion of wave energy in electrical one has been increasingly studied. One example of wave energy converter (WEC) is the overtopping device. Its main operational principle consists of a ramp which guides the incoming waves into a reservoir raised slightly above the sea level. The accumulated water in the reservoir flows through a low head turbine generating electricity. In this sense, it is performed a numerical study concerned with the geometric optimization of an overtopping WEC for various relative depths:d/λ = 0.3, 0.5 and 0.62, by means of Constructal Design. The main purpose is to evaluate the effect of the relative depth on the design of the ramp geometry (ratio between the ramp height and its length:H1/L1) as well as, investigate the shape which leads to the highest amount of water that insides the reservoir. In the present simulations, the conservation equations of mass, momentum and one equation for the transport of volumetric fraction are solved with the finite volume method (FVM). To tackle with water-air mixture, the multiphase model Volume of Fluid (VOF) is used. Results showed that the optimal shape, (H1/L1)o, has a strong dependence of the relative depth, i.e., there is no universal shape that leads to the best performance of an overtopping device for several wave conditions.
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KOMATSU, Toshimitsu, Nobuhiro MATSUNAGA, Misao HASHIDA, Tomonari OKADA und Kazuo FUJITA. „Volume of Wave Overtopping Gained Effectively by a 3-D Structure“. PROCEEDINGS OF HYDRAULIC ENGINEERING 38 (1994): 493–97. http://dx.doi.org/10.2208/prohe.38.493.
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Gaeta, Maria Gabriella, Massimo Guerrero, Sara Mizar Formentin, Giuseppina Palma und Barbara Zanuttigh. „Non-Intrusive Measurements of Wave-Induced Flow over Dikes by Means of a Combined Ultrasound Doppler Velocimetry and Videography“. Water 12, Nr. 11 (30.10.2020): 3053. http://dx.doi.org/10.3390/w12113053.
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The performance of non-intrusive instruments, such as acoustic profilers and cameras, to describe the wave-induced flow processes over maritime dike crest was investigated in experiments carried out at the University of Bologna. Direct and derived measurements from the acoustic probes deployed along the structure crest were discussed in relation to the observed backscatter rates. Image processing was implemented by means of clustering algorithm, in order to detect the free surface during overtopping events and characterize wave front propagation over the dike crest. UVP data were processed to indirectly derive flow depths and overtopping rates and compare them with the direct measurements in order to assess the measurement reliability and discuss their limits. Individual overtopping volume distribution as obtained by UVP data were estimated and compared with well-consolidated formulations, showing a good agreement. Finally, suggestions for an appropriate use of non-intrusive instruments to characterize a shallow, transient and aerated flow were provided, such as the control of the artificial seeding density, the use of a bi-static UVP configuration and adjustments to light exposure.
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Li, Meng-Syue, Cheng-Jung Hsu, Hung-Chu Hsu und Li-Hung Tsai. „Numerical Analysis of Vertical Breakwater Stability under Extreme Waves“. Journal of Marine Science and Engineering 8, Nr. 12 (03.12.2020): 986. http://dx.doi.org/10.3390/jmse8120986.
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The purpose of this study is to perform a numerical simulation of caisson breakwater stability concerning the effect of wave overtopping under extreme waves. A numerical model, which solves two-dimensional Reynolds-averaged Navier–Stokes equations with the k−ε turbulence closure and uses the volume of fluid method for surface capturing, is validated with the laboratory observations. The numerical model is shown to accurately predict the measured free-surface profiles and the wave pressures around a caisson breakwater. Considering the dynamic loading on caisson breakwaters during overtopping waves, not only landward force and lift force but also the seaward force are calculated. Model results suggest that the forces induced by the wave overtopping on the back side of vertical breakwater and the phase lag of surface elevations have to be considered for calculating the breakwater stability. The numerical results also show that the failure of sliding is more dangerous than the failure of overturning in the vertical breakwater. Under extreme waves with more than 100 year return period, the caisson breakwater is sliding unstable, whereas it is safe in overturning stability. The influence of wave overtopping on the stability analysis is dominated by the force on the rear side of the caisson and the phase difference on the two ends of caisson. For the case of extreme conditions, if the impulse force happens at the moment of the minimum of load in the rear side, the safety factor might decrease significantly and the failure of sliding might cause breakwater damage. This paper demonstrates the potential stability failure of coastal structures under extreme sea states and provides adapted formulations of safety factors in dynamic form to involve the influence of overtopping waves.
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Hübner, R. G., P. H. Oleinik, W. C. Marques, M. N. Gomes, E. D. dos Santos, B. N. Machado und L. A. Isoldi. „NUMERICAL STUDY COMPARING THE INCIDENCE INFLUENCE BETWEEN REALISTIC WAVE AND REGULAR WAVE OVER AN OVERTOPPING DEVICE“. Revista de Engenharia Térmica 18, Nr. 1 (03.06.2019): 46. http://dx.doi.org/10.5380/reterm.v18i1.67047.
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This work presents a numerical study to evaluate the difference between the fluid dynamic behavior of an overtopping device subjected to the incidence of a realistic wave when compared to a regular one; being this regular wave representative of the considered realistic sea state. To do so, the FLUENT software was employed, which is a Computational Fluid Dynamics package based on the Finite Volume Method. The regular wave was generated through a User Defined Function (UDF) that imposes its velocities components as boundary conditions of prescribed velocity. On the other hand, for the realistic wave it was used a methodology to impose the realistic components velocities from transient discrete values, named Table Data (TD) in FLUENT software. For both cases the Volume of Fluid (VOF) multiphase model was applied in the treatment of the water-air interaction. The results showed that the amount of water accumulated in the reservoir for the realistic sea state was 2.46 higher than for the regular wave. This is a relevant finding, since several researches about Overtopping device efficiency were promoted considering only the incidence of regular wave.
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Lee, Cheol-Eung. „Reliability Analysis of Maximum Overtopping Volume for Evaluating Freeboard of Vertical Breakwaters“. Journal of Korean Society of Coastal and Ocean Engineers 23, Nr. 2 (29.04.2011): 154–62. http://dx.doi.org/10.9765/kscoe.2011.23.2.154.
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Hughes, Steven A., und Christopher I. Thornton. „Estimation of time-varying discharge and cumulative volume in individual overtopping waves“. Coastal Engineering 117 (November 2016): 191–204. http://dx.doi.org/10.1016/j.coastaleng.2016.08.006.
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Gomes, Mateus das Neves, Maria Fernanda Espinel Lara, Silvana Letícia Pires Iahnke, Bianca Neves Machado, Marcelo Moraes Goulart, Flávio Medeiros Seibt, Elizaldo Domingues dos Santos, Liércio André Isoldi und Luiz Alberto Oliveira Rocha. „Numerical Approach of the Main Physical Operational Principle of Several Wave Energy Converters: Oscillating Water Column, Overtopping and Submerged Plate“. Defect and Diffusion Forum 362 (April 2015): 115–71. http://dx.doi.org/10.4028/www.scientific.net/ddf.362.115.
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In this work it is numerically studied the wave flow inside a tank and the main operational physical principle of three different wave energy converters (WEC): oscillating water column (OWC), overtopping and submerged plate. The wave energy converters are evaluated in laboratory and real scales. For all studied cases the conservation equations of mass, momentum and one equation for the transport of volumetric fraction are solved with the finite volume method (FVM). To tackle with water-air mixture, the multiphase model Volume of Fluid (VOF) is used. Several results showed the accuracy of the numerical approach for estimation of the physical phenomenon of wave flow inside tanks, as well as, its interaction with the studied devices. For the cases with geometrical optimization, Constructal Design is employed for geometrical evaluation of the devices. Results presented several theoretical recommendations about the influence of geometrical parameters (such as ratios between heights and lengths of OWC chamber and ramp of overtopping device and the distance from the plate to the seabed of wave tank) over the available power take off (PTO) in the OWC and submerged plate devices and over the amount of water stored in the reservoir of the overtopping device. Results showed the importance of geometric shapes over the devices performance. Moreover, it is evaluated the influence of several wave parameters (such as wave period and relative depths) over the fluid dynamic performance of the devices and geometrical parameters of the devices. It is noticed the non-occurrence of universal optimal shapes.
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Guan, Dawei, Jingang Liu, Yee-Meng Chiew und Yingzheng Zhou. „Scour Evolution Downstream of Submerged Weirs in Clear Water Scour Conditions“. Water 11, Nr. 9 (22.08.2019): 1746. http://dx.doi.org/10.3390/w11091746.
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Although weirs or dikes in the riverine and coastal environments are frequently overtopped, few studies have hitherto examined the evolution of the scour process downstream of these structures under the submerged condition. This paper presents an experimental investigation on time evolution of the scour process downstream of submerged weirs with a uniform coarse sand. The clear-water scour experiments were carried out in a tilting recirculation flume. Different flow intensities and overtopping ratios (approach flow depth/weir height) were adopted in the experiments. Experimental observations show that the scour hole downstream of submerged weirs develops very fast in the initial stage, before progressing at a decreasing rate and eventually reaching the equilibrium stage. The results show that an increase of the overtopping ratio or flowrate can generate larger scour depth and volume downstream of the weir. Moreover, geometrical similarity of the scour hole that formed downstream of the weir was observed in the tests. Finally, empirical equations for predicting scour hole geometrical evolutions downstream of the submerged weirs were presented. The results of this study are useful in the development of numerical/analytical models capable of estimating the scour depth downstream of weirs in the river or coastal areas, for which the overtopping conditions are present.
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Hosseinzadeh-Tabrizi, Seyed Alireza, und Mahnaz Ghaeini-Hessaroeyeh. „Application of Bed Load Formulations for Dam Failure and Overtopping“. Civil Engineering Journal 3, Nr. 10 (04.11.2017): 997. http://dx.doi.org/10.28991/cej-030932.
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The Enhanced HLLC scheme as a robust approximate Riemann solver is used for numerical modeling of three different test cases of mobile bed and stepped mobile bed in dam failure and dam overtopping conditions. The current research has been done in the frame of the finite volume method using shallow water equations along with the Exner equation for sediment continuity. The Ribberink, Wong and Parker formulations have been used for the modelling of bed load movement. A convenient approach based on the Boussinesq hypothesis is deployed for considering turbulence effects in the second case. The affections of stepped and slope condition for the flow bed are considered through a corrected version of the HLLC flux components. Finally, the model is applied for modelling overtopping in the third case. The results of the present model are relatively reasonable by comparing with the experimental data.
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Didier, E., D. R. C. B. Neves, R. Martins und M. G. Neves. „MODELLING OF HYDRODYNAMICS AROUND AN IMPERMEABLE BREAKWATER: COMPARISON BETWEEN PHYSICAL AND SPH NUMERICAL MODELING“. Revista de Engenharia Térmica 11, Nr. 1-2 (31.12.2012): 68. http://dx.doi.org/10.5380/reterm.v11i1-2.62003.
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This work presents the new developments and the validation of a Smoothed Particle Hydrodynamics (SPH) numerical model used in the National Laboratory of Civil Engineering (Laboratório Nacional de Engenharia Civil - LNEC) for studies in coastal engineering processes. Although the model requires a high CPU time, it proved to be very promising in the simulation of complex flows, such as the wave-structure interaction and the wave breaking phenomenon. For the SPH model validation, physical modeling tests were performed in one LNEC’s flume to study the interaction between an impermeable structure and an incident regular wave. The comparison between numerical and experimental results, i.e. free surface elevation, overtopping volume and pressure, shows the good accuracy of the SPH model to reproduce the various phenomena involving on the wave propagation and interaction with the structure, namely the wave breaking, the wave overtopping and the pressure field on the structure.
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Tan, Lai Wai, und Vincent H. Chu. „REGULAR PERIODIC WAVE RUNUP AND OVERTOPPING SIMULATIONS BY LAGRANGIAN BLOCKS“. Coastal Engineering Proceedings 1, Nr. 32 (30.01.2011): 46. http://dx.doi.org/10.9753/icce.v32.currents.46.
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Wave runup and overtopping of truncated beaches have been simulated using the method of Lagrangian Block Hydrodynamics (LBH). Instead of interpolation, which causes numerical oscillations, the fluxes through the face of the finite-volume in the LBH method are determined by the advection of the blocks. Negative water depth is not possible and the computation is unconditionally stable as the momentum is updated by the re-construction of the blocks. The accuracy of the method is evaluated using (i) the exact solution of the collapsing bore and (ii) the available laboratory data of the solitary waves as the benchmarks. The numerical simulations carried out for regular periodic waves cover a wide range of wave steepness and beach slopes taking advantage of the inherent shock-capturing and shoreline-tracking capabilities of the LBH method.
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Michailidi, Eleni Maria, und Baldassare Bacchi. „Dealing with uncertainty in the probability of overtopping of a flood mitigation dam“. Hydrology and Earth System Sciences 21, Nr. 5 (12.05.2017): 2497–507. http://dx.doi.org/10.5194/hess-21-2497-2017.
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Abstract. In recent years, copula multivariate functions were used to model, probabilistically, the most important variables of flood events: discharge peak, flood volume and duration. However, in most of the cases, the sampling uncertainty, from which small-sized samples suffer, is neglected. In this paper, considering a real reservoir controlled by a dam as a case study, we apply a structure-based approach to estimate the probability of reaching specific reservoir levels, taking into account the key components of an event (flood peak, volume, hydrograph shape) and of the reservoir (rating curve, volume–water depth relation). Additionally, we improve information about the peaks from historical data and reports through a Bayesian framework, allowing the incorporation of supplementary knowledge from different sources and its associated error. As it is seen here, the extra information can result in a very different inferred parameter set and consequently this is reflected as a strong variability of the reservoir level, associated with a given return period. Most importantly, the sampling uncertainty is accounted for in both cases (single-site and multi-site with historical information scenarios), and Monte Carlo confidence intervals for the maximum water level are calculated. It is shown that water levels of specific return periods in a lot of cases overlap, thus making risk assessment, without providing confidence intervals, deceiving.
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Nicolae Lerma, Alexandre, Thomas Bulteau, Sylvain Elineau, François Paris, Paul Durand, Brice Anselme und Rodrigo Pedreros. „High-resolution marine flood modelling coupling overflow and overtopping processes: framing the hazard based on historical and statistical approaches“. Natural Hazards and Earth System Sciences 18, Nr. 1 (17.01.2018): 207–29. http://dx.doi.org/10.5194/nhess-18-207-2018.
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Abstract. A modelling chain was implemented in order to propose a realistic appraisal of the risk in coastal areas affected by overflowing as well as overtopping processes. Simulations are performed through a nested downscaling strategy from regional to local scale at high spatial resolution with explicit buildings, urban structures such as sea front walls and hydraulic structures liable to affect the propagation of water in urban areas. Validation of the model performance is based on hard and soft available data analysis and conversion of qualitative to quantitative information to reconstruct the area affected by flooding and the succession of events during two recent storms. Two joint probability approaches (joint exceedance contour and environmental contour) are used to define 100-year offshore conditions scenarios and to investigate the flood response to each scenario in terms of (1) maximum spatial extent of flooded areas, (2) volumes of water propagation inland and (3) water level in flooded areas. Scenarios of sea level rise are also considered in order to evaluate the potential hazard evolution. Our simulations show that for a maximising 100-year hazard scenario, for the municipality as a whole, 38 % of the affected zones are prone to overflow flooding and 62 % to flooding by propagation of overtopping water volume along the seafront. Results also reveal that for the two kinds of statistic scenarios a difference of about 5 % in the forcing conditions (water level, wave height and period) can produce significant differences in terms of flooding like +13.5 % of water volumes propagating inland or +11.3 % of affected surfaces. In some areas, flood response appears to be very sensitive to the chosen scenario with differences of 0.3 to 0.5 m in water level. The developed approach enables one to frame the 100-year hazard and to characterize spatially the robustness or the uncertainty over the results. Considering a 100-year scenario with mean sea level rise (0.6 m), hazard characteristics are dramatically changed with an evolution of the overtopping ∕ overflowing process ratio and an increase of a factor 4.84 in volumes of water propagating inland and 3.47 in flooded surfaces.
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Ibrahim, Muhammad S. I., und Tom E. Baldock. „Swash overtopping on plane beaches – Reconciling empirical and theoretical scaling laws using the volume flux“. Coastal Engineering 157 (April 2020): 103668. http://dx.doi.org/10.1016/j.coastaleng.2020.103668.
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Dumberry, Kevin, François Duhaime und Yannic A. Ethier. „Erosion monitoring during core overtopping using a laboratory model with digital image correlation and X-ray microcomputed tomography“. Canadian Geotechnical Journal 55, Nr. 2 (Februar 2018): 234–45. http://dx.doi.org/10.1139/cgj-2016-0684.
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Core overtopping in embankment dams is an important phenomenon that may lead to contact erosion along the core–filter interface. This paper presents new experimental results regarding erosion mechanisms at the core–filter interface during core overtopping. The experimental results were obtained using a reduced-scale model with a variable upstream water level. Digital image correlation (DIC), microcomputed tomography (μCT), and sediment collection at the outlet were used to quantify erosion. Four experimental runs were conducted with a till core and different filters. Only one of the four filters satisfied the filter criteria that were applied. No contact erosion occurred during this test. For filters that did not respect the filter criteria, piping occurred within the core along the downstream slope when the water level reached the top of the core. As a result of the self-healing process within the core material, the erosion rate decayed with time as the hydraulic gradient increased. Results for DIC mainly reflected settlements within the filter due to erosion and a soil arching effect. The magnitude of the displacement vector obtained with DIC is directly proportional to the volume of till eroded. μCT showed that contact erosion occurred continuously.
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Gabl, R., J. Seibl, B. Gems und M. Aufleger. „3-D numerical approach to simulate the overtopping volume caused by an impulse wave comparable to avalanche impact in a reservoir“. Natural Hazards and Earth System Sciences 15, Nr. 12 (09.12.2015): 2617–30. http://dx.doi.org/10.5194/nhess-15-2617-2015.
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Abstract. The impact of an avalanche in a reservoir induces impulse waves, which pose a threat to population and infrastructure. For a good approximation of the generated wave height and length as well as the resulting overtopping volume over structures and dams, formulas, which are based on different simplifying assumptions, can be used. Further project-specific investigations by means of a scale model test or numerical simulations are advisable for complex reservoirs as well as the inclusion of hydraulic structures such as spillways. This paper presents a new approach for a 3-D numerical simulation of the avalanche impact in a reservoir. In this model concept the energy and mass of the avalanche are represented by accelerated water on the actual hill slope. Instead of snow, only water and air are used to simulate the moving avalanche with the software FLOW-3D. A significant advantage of this assumption is the self-adaptation of the model avalanche onto the terrain. In order to reach good comparability of the results with existing research at ETH Zürich, a simplified reservoir geometry is investigated. Thus, a reference case has been analysed including a variation of three geometry parameters (still water depth in the reservoir, freeboard of the dam and reservoir width). There was a good agreement of the overtopping volume at the dam between the presented 3-D numerical approach and the literature equations. Nevertheless, an extended parameter variation as well as a comparison with natural data should be considered as further research topics.
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Stansby, Peter K. „Solitary wave run up and overtopping by a semi-implicit finite-volume shallow-water Boussinesq model“. Journal of Hydraulic Research 41, Nr. 6 (November 2003): 639–47. http://dx.doi.org/10.1080/00221680309506896.
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Cain, Michael D., und James P. Barnett. „An 8-year field comparison of naturally seeded to planted container Pinustaeda, with and without release“. Canadian Journal of Forest Research 26, Nr. 7 (01.07.1996): 1237–47. http://dx.doi.org/10.1139/x26-138.
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A field study compared genetically improved, container loblolly pines (Pinustaeda L.) with naturally seeded loblolly pines through eight growing seasons on a cutover site in southern Arkansas, U.S.A. Measurement pines on 6 of 12 plots were released from woody and herbaceous competition within a 61-cm radius of each tree stem. On natural pine plots, only 1st-year pine seedlings were selected for measurement based on quality standards and their spacing. Woody competition was controlled by hand cutting for 5 consecutive years, and herbaceous competition was controlled with herbicides for 4 consecutive years. Release treatments increased 8-year survival by 50% for natural pines and by 35% for planted pines. Greater gains (343–391%) in individual tree volumes were achieved within regeneration techniques, as a result of release, than were achieved with the two regeneration techniques. In addition, stand volume gains of 647% and 910% were achieved by planted and natural pines, respectively, as a result of release. Eight years after field establishment, stand volume index averaged 46% higher on planted plots than on natural plots. Degree of overtopping was a better predictor of pine performance than live-crown ratio.
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Cavallaro, Luca, Fabio Dentale, Giovanna Donnarumma, Enrico Foti, Rosaria E. Musumeci und Eugenio Pugliese Carratelli. „RUBBLE MOUND BREAKWATER OVERTOPPING: ESTIMATION OF THE RELIABILITY OF A 3D NUMERICAL SIMULATION“. Coastal Engineering Proceedings 1, Nr. 33 (25.10.2012): 8. http://dx.doi.org/10.9753/icce.v33.structures.8.
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Until recently, physical models were the only way to investigate into the details of breakwaters behavior under wave attack. From the numerical point of view, the complexity of the fluid dynamic processes involved has so far hindered the direct application of Navier-Stokes equations within the armour blocks, due to the complex geometry and the presence of strongly non stationary flows, free boundaries and turbulence. In the present work the most recent CFD technology is used to provide a new and more reliable approach to the design analysis of breakwaters, especially in connection with run-up and overtopping. The solid structure is simulated within the numerical domain by overlapping individual virtual elements to form the empty spaces delimited by the blocks. Thus, by defining a fine computational grid, an adequate number of nodes is located within the interstices and a complete solution of the full hydrodynamic equations is carried out. In the work presented here the numerical simulations are carried out by integrating the three-dimensional Reynolds Average Navier-Stokes Equations coupled with the RNG turbulence model and a Volume of Fluid Method used to handle the dynamics of the free surface. The aim of the present work is to investigate the reliability of this approach as a design tool. Two different breakwaters are considered, both located in Southern Sicily: one a typical quarry stone breakwater, another a more complex design incorporating a spill basin and an armoured layer made up by Coreloc® blocks.
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Olson, Matthew G., Robert G. Wagner und John C. Brissette. „Forty years of spruce–fir stand development following herbicide application and precommercial thinning in central Maine, USA“. Canadian Journal of Forest Research 42, Nr. 1 (Januar 2012): 1–11. http://dx.doi.org/10.1139/x11-132.
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We examined the development of a 33-year experiment in spruce–fir stands that received nine herbicide treatments (applied aerially in 1977), with and without precommercial thinning (PCT) (applied in 1986). We tested two commonly held assumptions about the long-term effects of herbicide and PCT in mixedwood stands managed for softwoods: (i) herbicide release produces stands dominated by softwoods and (ii) PCT promotes both softwood dominance and merchantable volume. All herbicides were effective at releasing balsam fir ( Abies balsamea (L.) Mill.) and spruce ( Picea spp.) from overtopping shrubs and hardwoods that had naturally regenerated following clearcut harvesting in 1970. Glyphosate (Roundup), triclopyr amine (Garlon 3A), 2,4,5-T, and a mixture of 2,4,5-T and 2,4-D herbicide treatments were all effective at shifting long-term species composition to softwood dominance after 30 years, irrespective of the rates applied. Herbicide-treated stands that did not receive PCT were overstocked with softwoods for at least 24 years and produced less than half of the merchantable softwood volume by 40 years than herbicide-treated stands that received PCT. Intolerant hardwoods dominated untreated stands for all 33 years of the experiment. When unsprayed plots received PCT, however, they produced stands at 40 years that were compositionally and structurally indistinguishable from those that had received both herbicide and PCT treatments. Results from this experiment clearly demonstrated that early herbicide application, regardless of type and rate of herbicide, created softwood-dominated mixedwood stands over the long term and that PCT more than doubled merchantable softwood volume within 25 years of application.
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Nicholls, Robert J., Lauren Burt, Joel Smethurst und Charlotte Thompson. „IMPLICATIONS OF CONSOLIDATION ON BARRIER BEACH STABILITY“. Coastal Engineering Proceedings, Nr. 36 (30.12.2018): 67. http://dx.doi.org/10.9753/icce.v36.sediment.67.
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Barrier beaches often overlie backbarrier deposits composed of poorly consolidated sediments. Hence, they can consolidate significantly if loaded. A retreating barrier beach provides such a load. In the static situation of beach nourishment, the increased load of the raised beach volume will also cause increased consolidation. These can lower beach elevation promoting wave overtopping, overwashing and retreat. However, there is limited research concerning the role of consolidation on the stability of barrier beaches worldwide. This paper focuses on this issue using Hurst Spit on the UK south coast as a study site where consolidation is a known significant process (Nicholls, 1985; Burt et al., 2018). It is a storm beach composed of shingle (pebble and cobble) sediments and formerly retreated at 2 to 3 m/yr, Since the later 1990s it has been more stabilized by a major nourishment (Bradbury and Kidd, 1998), but continues to retreat slowly (Figure 1). A second nourishment phase is now being actively assessed following major damage in the large storm of 14 February 2014. In this context, the role of consolidation has been analyzed via new data collection, consolidation modelling and morphodynamic modelling. This paper presents these results and their implications.
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Itzkin, Michael, Laura J. Moore, Peter Ruggiero, Sally D. Hacker und Reuben G. Biel. „The relative influence of dune aspect ratio and beach width on dune erosion as a function of storm duration and surge level“. Earth Surface Dynamics 9, Nr. 5 (13.09.2021): 1223–37. http://dx.doi.org/10.5194/esurf-9-1223-2021.
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Abstract. Dune height is an important predictor of impact during a storm event given that taller dunes have a lower likelihood of being overtopped than shorter dunes. However, the temporal dominance of the wave collision regime, wherein volume loss (erosion) from the dune occurs through dune retreat without overtopping, suggests that dune width must also be considered when evaluating the vulnerability of dunes to erosion. We use XBeach, a numerical model that simulates hydrodynamic processes, sediment transport, and morphologic change, to analyze storm-induced dune erosion as a function of dune aspect ratio (i.e., dune height versus dune width) for storms of varying intensity and duration. We find that low aspect ratio (low and wide) dunes lose less volume than high aspect ratio (tall and narrow) dunes during longer and more intense storms when the beach width is controlled for. In managed dune scenarios, where sand fences are used to construct a “fenced” dune seaward of the existing “natural” dune, we find that fenced dunes effectively prevent the natural dune behind them from experiencing any volume loss until the fenced dune is sufficiently eroded, reducing the magnitude of erosion of the natural dune by up to 50 %. We then control for dune morphology to assess volume loss as a function of beach width and confirm that beach width exerts a significant influence on dune erosion; a wide beach offers the greatest protection from erosion in all circumstances while the width of the dune determines how long the dune will last under persistent scarping. These findings suggest that efforts to maintain a wide beach may be effective at protecting coastal communities from dune loss. However, a trade-off may exist in maintaining wide beaches and dunes in that the protection offered in the short-term must be considered in concert with potentially long-term detrimental effects of limiting overwash, a process which is critical to maintaining island elevation as sea level rises.
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Sentani, Ari, Didier Marot und Fateh Bendahmane. „Erodibility of Granular Materials Models“. Journal of Advanced Civil and Environmental Engineering 1, Nr. 2 (31.10.2018): 49. http://dx.doi.org/10.30659/jacee.1.2.49-56.
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Abstract: Two means physical processes are involved in failure of a dams structure: either a mechanical failure by sliding, or a hydraulic failure by erosion. The causes of failures are internal erosion (23 cases between 44), or external erosion (20 cases of overtopping) and 1 case of sliding. In consequence, internal erosion is the most frequent cause for all the water retaining structures. A series of test are needed to develop models that can describe the internal erosion. This research uses two kinds of tests. They are The Consodilated Drained (CD) Triaxial test and The Erodibility test with triaxial erodimetre. These two tests uses mixture between Kaolinite Proclay (25%) and Fontainebleau Sand (75%) with 9% of water content. The result shows that confinement pressure increase, time for obtained maximal deviatoric also increase. When deviatoric stress is increase, percentage of deformation is also increase. And also the volume variation of specimen is decrease in function of deformation. For the second test, the result shows after the loss of fine particles in the soil, the original dilative stress-strain behavior changes to be contractive and the peak stress is decreases. Comparing the results of Chang & Zhang in 2011, the curves rank in a coherent way for the stress-strain curve although it used different speciments.
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Jiang, Changbo, Xiaojian Liu, Yu Yao, Bin Deng und Jie Chen. „Numerical Investigation of Tsunami-Like Solitary Wave Interaction with a Seawall“. Journal of Earthquake and Tsunami 11, Nr. 01 (März 2017): 1740006. http://dx.doi.org/10.1142/s1793431117400061.
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Seawall is a most commonly used structure in coastal areas to protect the landscape and coastal facilities. The studies of interactions between the tsunami-like solitary waves and the seawalls are relatively rare in the literature. In this study, a three-dimensional numerical model based on OpenFOAM® was developed to investigate the tsunami-like solitary waves propagating over a rectangular seawall. The Navier–Stokes equations for two-phase incompressible flow, combining with methods of [Formula: see text] for turbulence closure and Volume of Fluid (VOF) for tracking the free surface, were solved. Laboratory experiments were performed to measure some of the hydrodynamic feature associated with solitary waves. The model was then validated by the laboratory data, and good agreements were found for free surface, velocity and dynamic pressure around the seawall. Finally, a series of numerical experiments were conducted to analyze the evolution of both wave and flow fields, the overtopping discharge as well as wave pressure (force) around the seawall, special attention is given to the effects of seawall crest width. Our findings will help to improve the understanding in the occurrences of tsunami-induced damages in the vicinity of seawall such as wave impact and local scouring.
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Fourie, A. B., G. E. Blight und G. Papageorgiou. „Static liquefaction as a possible explanation for the Merriespruit tailings dam failure“. Canadian Geotechnical Journal 38, Nr. 4 (01.08.2001): 707–19. http://dx.doi.org/10.1139/t00-112.
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In 1994 the Merriespruit gold tailings dam in South Africa failed, resulting in 17 deaths. The post-failure investigation provided no explanation as to why the catastrophic flow failure, which contradicted all previous experiences of failures of gold tailings dams in South Africa, occurred. The documented history of the dam describes insufficient freeboard provision and often poor pool control, which is argued to have resulted in some areas of the dam having high in situ void ratios. Some of the undrained triaxial tests carried out on specimens obtained from zones adjacent to the failure scar exhibited nondilative behaviour. Laboratory triaxial tests that were conducted on reconstituted specimens and are reported in a companion paper defined a series of steady state lines that were dependent on the particle-size distribution of the tailings. Void ratios obtained from undisturbed samples taken during the post-failure investigation are compared with these steady state lines and it is shown that an appreciable percentage of the specimens were likely to have been contractant. The inference drawn is that a large volume of tailings was in a metastable state in situ and overtopping and erosion of the impoundment wall exposed this material, resulting in static liquefaction of the tailings and a consequent flow failure.Key words: static liquefaction, gold tailings, Merriespruit, failure.
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Crochemore, Louise, Maria-Helena Ramos, Florian Pappenberger, Schalk Jan van Andel und Andrew W. Wood. „An Experiment on Risk-Based Decision-Making in Water Management Using Monthly Probabilistic Forecasts“. Bulletin of the American Meteorological Society 97, Nr. 4 (01.04.2016): 541–51. http://dx.doi.org/10.1175/bams-d-14-00270.1.
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Abstract The use of probabilistic forecasts is necessary to take into account uncertainties and allow for optimal risk-based decisions in streamflow forecasting at monthly to seasonal lead times. Such probabilistic forecasts have long been used by practitioners in the operation of water reservoirs, in water allocation and management, and more recently in drought preparedness activities. Various studies assert the potential value of hydrometeorological forecasting efforts, but few investigate how these forecasts are used in the decision-making process. Role-playing games can help scientists, managers, and decision-makers understand the extremely complex process behind risk-based decisions. In this paper, we present an experiment focusing on the use of probabilistic forecasts to make decisions on reservoir outflows. The setup was a risk-based decision-making game, during which participants acted as water managers. Participants determined monthly reservoir releases based on a sequence of probabilistic inflow forecasts, reservoir volume objectives, and release constraints. After each decision, consequences were evaluated based on the actual inflow. The analysis of 162 game sheets collected after eight applications of the game illustrates the importance of leveraging not only the probabilistic information in the forecasts but also predictions for a range of lead times. Winning strategies tended to gradually empty the reservoir in the months before the peak inflow period to accommodate its volume and avoid overtopping. Twenty percent of the participants managed to do so and finished the management period without having exceeded the maximum reservoir capacity or violating downstream release constraints. The role-playing approach successfully created an open atmosphere to discuss the challenges of using probabilistic forecasts in sequential decision-making.
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Dong, Shudi, Soroush Abolfathi, Md Salauddin und Jonathan Pearson. „SPATIAL DISTRIBUTION OF WAVE-BY-WAVE OVERTOPPING AT VERTICAL SEAWALLS“. Coastal Engineering Proceedings, Nr. 36v (28.12.2020): 17. http://dx.doi.org/10.9753/icce.v36v.structures.17.
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Over the years, many physical and numerical modelling research has been carried out to investigate the wave-structure interactions and the resulting mean overtopping characteristics at sea defences. The most reliable empirical predication formulae for prediction of mean overtopping rates have been reported in the overtopping manual, EurOtop (2018). In addition to average overtopping rates, in recent years, the spatial distribution of overtopped water has become an important topic of research to understand the safe zone behind coastal defences. The existing empirical formulae for spatial distribution of overtopping provide conservative predictions, as it has been derived from the mean overtopping volumes. The extreme wave overtopping hazards in generally originate from individual overtopping events rather than the mean overtopping volumes. This study presents comprehensive laboratory investigations on the spatial distribution of wave-by-wave overtopping at vertical seawalls.
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Baker, James B., und Michael G. Shelton. „Rehabilitation of Understocked Loblolly-Shortleaf Pine Stands—IV. Natural and Planted Seedling/Sapling Stands“. Southern Journal of Applied Forestry 22, Nr. 1 (01.02.1998): 53–59. http://dx.doi.org/10.1093/sjaf/22.1.53.
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Abstract A 3- to 6-yr-old naturally regenerated even-aged loblolly pine (Pinus taeda L.) stand and a 5-yr-old loblolly pine plantation on good sites (SILob = 85 to 90 ft at 50 yr) were cut to density levels of 50, 90, 180, 270, and 360 seedlings and/or saplings/ac. Two pine release treatments (none and individual tree release with a herbicide) were applied to the natural stand, but were not imposed in the plantation because site preparation treatments were applied before planting. At 2, 5, and 10 yr after installation, plots were inventoried to determine: (1) the lowest threshold of seedling/sapling density that was feasible to manage, (2) the time required for poorly stocked seedling/sapling stands to reach an acceptable stocking level, and (3) whether release treatments would improve survival and growth of understocked, natural seedling/sapling stands. Results indicated that loblolly pine plantations on good sites having at least 180 trees/ac (30% stocking) reached an acceptable stocking level of 60% by age 10 and produced up to 1,500 ft³/ac (19 cd/ac) of merchantable volume by age 15. By this age, trees in plantations with 270 and 360 trees/ac displayed good form, but at densities of 180, 90, and 50 trees/ac the trees still retained large branches nearly to the ground. Natural stands having at least 180 trees/ac that were released from overtopping by hardwood at age 5 reached 60% stocking by age 15 but produced only 627 ft³/ac (8 cd/ac) of merchantable volume. When pines in the natural stand were not released, only plots with 360 trees/ac reached an acceptable 60% stocking level by age 15 but only produced 539 ft³/ac (7 cd/ac) of merchantable volume. The observed differences in recovery rates in the understocked pine stands principally reflected the levels of competing hardwoods. Results suggest that understocked, natural stands or plantations of pine seedlings/saplings with fewer than 180 trees/ac (less than 30% stocking), at age 5, should probably be liquidated and a new stand established unless the landowner is willing to sacrifice significant reductions in early volume production. South. J. Appl. For. 22(1)53-59.
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Troch, Peter, Charlotte Beels, Julien De Rouck und Griet De Backer. „WAKE EFFECTS BEHIND A FARM OF WAVE ENERGY CONVERTERS FOR IRREGULAR LONG-CRESTED AND SHORT-CRESTED WAVES“. Coastal Engineering Proceedings 1, Nr. 32 (01.02.2011): 53. http://dx.doi.org/10.9753/icce.v32.waves.53.
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The contribution of wave energy to the renewable energy supply is rising. To extract a considerable amount of wave power, Wave Energy Converters (WECs) are arranged in several rows or in a ’farm’. WECs in a farm are interacting (e.g. the presence of other WECs influence the operational behaviour of a single WEC) and the overall power absorption is affected. In this paper wake effects in the lee of a single WEC and multiple WECs of the overtopping type, where the water volume of overtopped waves is first captured in a basin above mean sea level and then drains back to the sea through hydro turbines, are studied using the time-dependent mild-slope equation model MILDwave. The wake behind a single WEC is investigated for long-crested and short-crested incident waves. The wake becomes wider for larger wave peak periods. An increasing directional spreading results in a faster wave regeneration and a shorter wake behind the WEC. The wake in the lee of multiple WECs is calculated for two different farm lay-outs, i.e. an aligned grid and a staggered grid, with varying lateral and longitudinal spacing. The wave power redistribution in and behind each farm lay-out is studied in detail using MILDwave. In general, the staggered grid results in the highest overall wave power absorption.
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Hughes, Steven A., Christopher I. Thornton, Jentsje W. Van der Meer und Bryan N. Scholl. „IMPROVEMENTS IN DESCRIBING WAVE OVERTOPPING PROCESSES“. Coastal Engineering Proceedings 1, Nr. 33 (25.10.2012): 35. http://dx.doi.org/10.9753/icce.v33.waves.35.
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This paper presents a new empirical relation for the shape factor in the Weibull distribution that describes the distribution of overtopping wave volumes. This improvement increases the applicable range of the Weibull distribution from very low average overtopping discharges to large discharges resulting from combined wave overtopping and steady surge overflow at negative freeboards. The effect this improvement has on wave overtopping simulation is also discussed. Measured maximum flow thicknesses, velocities, and discharges from experiments of combined wave and surge overtopping are examined to learn more about the variability of these key parameters as a function of individual overtopping wave volumes. A key finding is that wave volumes containing the 2%-exceedance value of maximum velocity typically have maximum flow thicknesses well below the 2%-exceedance level, and vice-versa. Furthermore, the 2%-exceedance hydrodynamic parameters do not occur in the 2%-exceedance wave volumes. Finally, empirical relationships are developed for several parameters that showed strong trends.