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  Subjects -> ENGINEERING (Total: 2279 journals)
    - CHEMICAL ENGINEERING (191 journals)
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    - ENGINEERING (1203 journals)
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ENGINEERING (1203 journals)                  1 2 3 4 5 6 7 | Last

Showing 1 - 200 of 1205 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 7)
3D Research     Hybrid Journal   (Followers: 19)
AAPG Bulletin     Full-text available via subscription   (Followers: 5)
AASRI Procedia     Open Access   (Followers: 15)
Abstract and Applied Analysis     Open Access   (Followers: 3)
Aceh International Journal of Science and Technology     Open Access   (Followers: 2)
ACS Nano     Full-text available via subscription   (Followers: 222)
Acta Geotechnica     Hybrid Journal   (Followers: 7)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 2)
Acta Scientiarum. Technology     Open Access   (Followers: 3)
Acta Universitatis Cibiniensis. Technical Series     Open Access  
Active and Passive Electronic Components     Open Access   (Followers: 7)
Adaptive Behavior     Hybrid Journal   (Followers: 11)
Adıyaman Üniversitesi Mühendislik Bilimleri Dergisi     Open Access  
Adsorption     Hybrid Journal   (Followers: 4)
Advanced Engineering Forum     Full-text available via subscription   (Followers: 6)
Advanced Science     Open Access   (Followers: 4)
Advanced Science Focus     Free   (Followers: 3)
Advanced Science Letters     Full-text available via subscription   (Followers: 5)
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Advances in Engineering Software     Hybrid Journal   (Followers: 25)
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Advances in Physics Theories and Applications     Open Access   (Followers: 12)
Advances in Polymer Science     Hybrid Journal   (Followers: 40)
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Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Aerobiologia     Hybrid Journal   (Followers: 1)
African Journal of Science, Technology, Innovation and Development     Hybrid Journal   (Followers: 4)
AIChE Journal     Hybrid Journal   (Followers: 29)
Ain Shams Engineering Journal     Open Access   (Followers: 5)
Akademik Platform Mühendislik ve Fen Bilimleri Dergisi     Open Access  
Alexandria Engineering Journal     Open Access   (Followers: 1)
AMB Express     Open Access   (Followers: 1)
American Journal of Applied Sciences     Open Access   (Followers: 28)
American Journal of Engineering and Applied Sciences     Open Access   (Followers: 11)
American Journal of Engineering Education     Open Access   (Followers: 9)
American Journal of Environmental Engineering     Open Access   (Followers: 16)
American Journal of Industrial and Business Management     Open Access   (Followers: 23)
Analele Universitatii Ovidius Constanta - Seria Chimie     Open Access  
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of Regional Science     Hybrid Journal   (Followers: 7)
Annals of Science     Hybrid Journal   (Followers: 7)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applicable Analysis: An International Journal     Hybrid Journal   (Followers: 1)
Applied Catalysis A: General     Hybrid Journal   (Followers: 6)
Applied Catalysis B: Environmental     Hybrid Journal   (Followers: 9)
Applied Clay Science     Hybrid Journal   (Followers: 4)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 12)
Applied Magnetic Resonance     Hybrid Journal   (Followers: 3)
Applied Nanoscience     Open Access   (Followers: 7)
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Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Physics Research     Open Access   (Followers: 3)
Applied Sciences     Open Access   (Followers: 2)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 4)
Arabian Journal for Science and Engineering     Hybrid Journal   (Followers: 5)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 4)
Archives of Foundry Engineering     Open Access  
Archives of Thermodynamics     Open Access   (Followers: 7)
Arid Zone Journal of Engineering, Technology and Environment     Open Access  
Arkiv för Matematik     Hybrid Journal   (Followers: 1)
ASEE Prism     Full-text available via subscription   (Followers: 3)
Asian Engineering Review     Open Access  
Asian Journal of Applied Science and Engineering     Open Access   (Followers: 1)
Asian Journal of Applied Sciences     Open Access   (Followers: 2)
Asian Journal of Biotechnology     Open Access   (Followers: 8)
Asian Journal of Control     Hybrid Journal  
Asian Journal of Current Engineering & Maths     Open Access  
Asian Journal of Technology Innovation     Hybrid Journal   (Followers: 8)
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
ATZagenda     Hybrid Journal  
ATZextra worldwide     Hybrid Journal  
Australasian Physical & Engineering Sciences in Medicine     Hybrid Journal   (Followers: 1)
Australian Journal of Multi-Disciplinary Engineering     Full-text available via subscription   (Followers: 2)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 8)
Avances en Ciencias e Ingeniería     Open Access  
Balkan Region Conference on Engineering and Business Education     Open Access   (Followers: 1)
Bangladesh Journal of Scientific and Industrial Research     Open Access  
Basin Research     Hybrid Journal   (Followers: 3)
Batteries     Open Access   (Followers: 4)
Bautechnik     Hybrid Journal   (Followers: 1)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 23)
Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 3)
BER : Manufacturing Survey : Full Survey     Full-text available via subscription   (Followers: 2)
BER : Motor Trade Survey     Full-text available via subscription   (Followers: 1)
BER : Retail Sector Survey     Full-text available via subscription   (Followers: 2)
BER : Retail Survey : Full Survey     Full-text available via subscription   (Followers: 2)
BER : Survey of Business Conditions in Manufacturing : An Executive Summary     Full-text available via subscription   (Followers: 3)
BER : Survey of Business Conditions in Retail : An Executive Summary     Full-text available via subscription   (Followers: 3)
Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
Biofuels Engineering     Open Access  
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 9)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 17)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 32)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 5)
Biomedical Microdevices     Hybrid Journal   (Followers: 8)
Biomedical Science and Engineering     Open Access   (Followers: 3)
Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 4)
BioNanoMaterials     Hybrid Journal   (Followers: 2)
Biotechnology Progress     Hybrid Journal   (Followers: 39)
Boletin Cientifico Tecnico INIMET     Open Access  
Botswana Journal of Technology     Full-text available via subscription  
Boundary Value Problems     Open Access   (Followers: 1)
Brazilian Journal of Science and Technology     Open Access   (Followers: 2)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
Bulletin of Canadian Petroleum Geology     Full-text available via subscription   (Followers: 14)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 3)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Hybrid Journal   (Followers: 14)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 41)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 7)
Case Studies in Thermal Engineering     Open Access   (Followers: 3)
Catalysis Communications     Hybrid Journal   (Followers: 6)
Catalysis Letters     Hybrid Journal   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysis Today     Hybrid Journal   (Followers: 5)
CEAS Space Journal     Hybrid Journal  
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 3)
Central European Journal of Engineering     Hybrid Journal   (Followers: 1)
CFD Letters     Open Access   (Followers: 6)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 2)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Engineering     Open Access   (Followers: 2)
Chinese Science Bulletin     Open Access   (Followers: 1)
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access   (Followers: 1)
Ciencias Holguin     Open Access   (Followers: 1)
CienciaUAT     Open Access  
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 11)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 14)
City, Culture and Society     Hybrid Journal   (Followers: 21)
Clay Minerals     Full-text available via subscription   (Followers: 9)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Coal Science and Technology     Full-text available via subscription   (Followers: 3)
Coastal Engineering     Hybrid Journal   (Followers: 11)
Coastal Engineering Journal     Hybrid Journal   (Followers: 4)
Coatings     Open Access   (Followers: 3)
Cogent Engineering     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Color Research & Application     Hybrid Journal   (Followers: 1)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 13)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 13)
Communications Engineer     Hybrid Journal   (Followers: 1)
Communications in Numerical Methods in Engineering     Hybrid Journal   (Followers: 2)
Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 25)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Composite Structures     Hybrid Journal   (Followers: 256)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 181)
Composites Part B : Engineering     Hybrid Journal   (Followers: 227)
Composites Science and Technology     Hybrid Journal   (Followers: 169)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
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Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
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Computers & Geosciences     Hybrid Journal   (Followers: 28)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 5)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 4)
Computers and Geotechnics     Hybrid Journal   (Followers: 10)
Computing and Visualization in Science     Hybrid Journal   (Followers: 5)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 29)
Conciencia Tecnologica     Open Access  
Concurrent Engineering     Hybrid Journal   (Followers: 3)
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 6)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 8)
Control Engineering Practice     Hybrid Journal   (Followers: 41)
Control Theory and Informatics     Open Access   (Followers: 7)
Corrosion Science     Hybrid Journal   (Followers: 25)
CT&F Ciencia, Tecnologia y Futuro     Open Access  

        1 2 3 4 5 6 7 | Last

Journal Cover Coastal Engineering
  [SJR: 1.999]   [H-I: 74]   [11 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0378-3839
   Published by Elsevier Homepage  [3034 journals]
  • Towards simulating floating offshore oscillating water column converters
           with Smoothed Particle Hydrodynamics
    • Abstract: Publication date: August 2017
      Source:Coastal Engineering, Volume 126
      Author(s): A.J.C. Crespo, C. Altomare, J.M. Domínguez, J. González-Cao, M. Gómez-Gesteira
      The mesh-free code DualSPHysics is applied to simulate the interaction between sea waves and an Oscillating Water Column device (OWC). In this work, capabilities and limitations of DualSPHysics are shown in simulating OWCs. On the one hand, the new capabilities of DualSPHysics are shown by simulating the effect of mooring systems on a floating offshore OWC. On the other hand, simulations only consider a single-phase (water) so that the full OWC behaviour is partially reproduced, i.e. air pressure fluctuations are not modelled. The model was first validated with one laboratory test that consists of a fixed OWC with an open chamber. Next, water surface oscillations inside the chamber of a real OWC (located in Mutriku, Spain) have been predicted using the prevalent wave conditions observed in the area. Finally, the capabilities of DualSPHysics were demonstrated by simulating an offshore OWC moored to the seabed.

      PubDate: 2017-06-11T12:02:46Z
       
  • Video-derived near bed and sheet flow sediment particle velocities in
           dam-break-driven swash
    • Abstract: Publication date: August 2017
      Source:Coastal Engineering, Volume 126
      Author(s): Jack A. Puleo, Douglas Krafft, José Carlos Pintado-Patiño, Brittany Bruder
      This short communication considers a video-based approach to quantify near bed and sheet flow swash zone sediment particle velocities over a mobile bed in a laboratory setting and relate the profile shape to sheet thickness and a velocity that can be measured outside the sheet layer (by for instance a current meter) Near bed high speed imagery was recorded during a dam-break driven swash event in a flume with optically clear walls. Repeated swash events for two different median sediment sizes were tested. Optical Current Meter (OCM) analysis was applied to bed parallel image time stacks extracted at elevations from below the at rest bed to within the lower water column. OCM results were compared to in situ velocity measurements, where possible, obtained with an acoustic Doppler profiling velocimeter (ADPV). OCM results compared well with ADPV measurements for moderate suspended sediment concentrations (based on visual observation; sediment concentrations were not measured). Too high of a sediment concentration over saturated the image and did not provide distinct sediment particle trajectories in a consistent direction for OCM analysis. This saturation occurred during uprush for both sediment sizes. Too little of a sediment concentration provided an inadequate number of sediment particle trajectories to track, such as during flow reversal for the coarser sediment. For coarser sediment, backwash velocities were well resolved in OCM analysis with velocities comparing well (correlation coefficient > 0.8) to ADPV estimates. The dimensionless backwash sheet flow sediment particle velocity profile (normalized by the velocity at the top of the sheet) scaled with the dimensionless elevation (normalized by the sheet layer thickness) to the 0.62 power with 95% confidence intervals for the exponent ranging from 0.47 to 0.76.

      PubDate: 2017-06-11T12:02:46Z
       
  • An overlapping domain decomposition based near-far field coupling method
           for wave structure interaction simulations
    • Abstract: Publication date: August 2017
      Source:Coastal Engineering, Volume 126
      Author(s): Xin Lu, Dominic Denver John Chandar, Yu Chen, Jing Lou
      This paper presents a newly developed Overlapping Domain Decomposition (ODD) method, which forms the basis of a near-far field coupling solver for a wide range of wave-structure interaction problems. In this method, the computational domain is decomposed into near and far fields which are then modeled separately by solving the viscous Navier-Stokes equations (NSE) and the Potential Laplacian equation (PLE) respectively. A Finite volume method (FVM) is adopted to discretize both the NS and PL equations. The free surface problem is solved in both domains but using totally different strategies. In the potential domain, a moving mesh free surface tracking method is adopted where arbitrary polyhedral mesh adapts to the time-varying shape of the interface using vertex-based automatic mesh motion solver. Meanwhile, at the free surface, the boundary conditions are formulated using an ordinary differential equation (ODE) derived from the Bernoulli's equation. In the viscous domain, however, the volume of fluid (VOF) method is used to predict the location of free surface. The novelty of the reported method lies in two-folds. First, the introduction of the so called overlapped buffer zone eliminates the need of performing time costing iterative schemes in the non-overlapping domain decomposition methods to ensure the matching of free surface elevation at the domain boundaries. The concept of a buffer zone is borrowed from the relaxation zone technique which is commonly used near the inlet to ensure a stable wave generation or near the outlet to absorb the reflected waves in numerical wave simulations. Second, an in-house developed OVERSET method is adopted for the viscous domain solver to handle large object displacement in the case of an extreme event. The proposed method has been implemented in the OpenFOAM platform (foam-extend-3.1). To validate the method, the propagation of a solitary wave is first simulated and the resulting wave parameters are compared with the corresponding analytical, as well as pure VOF solution. Meanwhile, a comparison of the CPU time between the single domain approach and the current method has been provided. Next, the measured wave impact loading for a single body which is partially submerged will be used to further test the method. Last but not least, the method is applied to simulate the spilling wave breaking near the beach. Various numerical examples presented in the paper demonstrate the accuracy and efficiency of the proposed method. Towards the end, computation of a sinking semi-submersible platform will be presented to demonstrate further the capability of the method.

      PubDate: 2017-06-11T12:02:46Z
       
  • Simulation of wave overtopping using an improved SPH method
    • Abstract: Publication date: August 2017
      Source:Coastal Engineering, Volume 126
      Author(s): H. Akbari
      An improved Smoothed Particle Hydrodynamics (SPH) method is used to study wave overtopping for different coastal structures. Simulated wave overtopping is too sensitive to the particle movements near the free surface boundary; however, the calculated flow acceleration by means of common SPH methods is not free of errors at this boundary due to the truncation of kernel function and contribution of fewer particles in solving the governing equations. In this paper, this problem is solved by modifying the viscosity of surface particles based on the concept of surface viscosity originally introduced by Xu (2010). By means of the introduced modification, unrealistic particle fluctuation at free surface boundary can be decreased significantly while keeping the model accuracy. This improvement can be used for both Incompressible and Weakly Compressible SPH methods and its implementation is easy and computationally efficient too. Different cases including dam break, solitary wave breaking and wave overtopping at vertical and sloping seawalls are simulated with the modified model and the new model is validated via comparing the results with several experimental and numerical data. Based on this study, free surface boundary can be simulated more accurately by means of the introduced modification and as a result, the predicted values particularly the calculated wave-overtopping rate become more reliable.

      PubDate: 2017-06-11T12:02:46Z
       
  • Experimental study of the hydraulic efficiency of a novel perforated-wall
           caisson concept, the LOWREB
    • Abstract: Publication date: August 2017
      Source:Coastal Engineering, Volume 126
      Author(s): Crina-Stefania Ciocan, Francisco Taveira-Pinto, Luciana das Neves, Paulo Rosa-Santos
      A novel perforated-wall caisson concept, the so-called LOW REflection Breakwater (LOWREB), based on a three-chamber perforated-wall and inner weirs, is under development in the University of Porto – Faculty of Engineering, Portugal. Physical model tests, carried out in the wave basin of the Hydraulics Laboratory of the Hydraulics, Water Resources and Environment Division, Civil Engineering Department, have been used to study the hydraulic processes related to wave reflection. The physical model was built to a Froude scale of 1:50. Test conditions covered two water levels and irregular waves at three significant wave heights (3.0, 4.0 and 5.0 m) and three peak wave periods (10, 14 and 18s). Three models of varying porosity, and vertical slots' arrangements were tested under the same hydrodynamic conditions to study how these affect the LOWREB performance, namely how these affect the wave reflection from the structure, as compared to a plain caisson tested under the same conditions. The experimental study demonstrates that the LOWREB caisson is a valid concept for marine structures, namely harbour breakwaters, because of its wave energy dissipation capacity, for which the inner weirs were found to play a major role. Results indicate that the hydraulic efficiency of the LOWREB caisson increases with wave height for the lower water level, and decreases with it for the highest. Greater efficiency with respect to wave reflection was accomplished with the highest water level.

      PubDate: 2017-06-11T12:02:46Z
       
  • Regional frequency analysis of extreme waves in a coastal area
    • Abstract: Publication date: August 2017
      Source:Coastal Engineering, Volume 126
      Author(s): C. Lucas, G. Muraleedharan, C. Guedes Soares
      This study analysed the wave data from several locations in a coastal region to identify the areas with comparable wave height statistics and to estimate regional extreme significant wave heights of designated return periods. The regional frequency analysis algorithm executed in this work utilised the significant wave height data from 35 sites (35°–45°N, -6.5°–-11.0°W) in a coastal grid (0.25° × 0.25°) off Portugal in the North Atlantic Ocean, extracted from 44 years HIPOCAS hindcast wave database. Regional frequency analysis algorithms based on L-moments identified the discordant sites (discordant site statistics are substantially diffused from the group of sites statistics), assisted in the formation of homogeneous regions by cluster analyses (data vectors include site characteristics and site statistics) and consequently selected appropriate regional frequency distributions by Z goodness-of-fit test statistic at 90% level of significance to estimate regional extreme significant wave height quantiles of designated return periods. The regional frequency analysis algorithm recognised in certain cases, neighbouring sites as members of diverse regions, revealing that geographical proximity of sites are not ascertaining factors to form homogeneous regions. At-site analyses along with regional frequency analysis enabled to apprehend the precision of the regional extreme quantile as genuine feature of its at-site extreme quantiles.

      PubDate: 2017-06-11T12:02:46Z
       
  • Nearshore placement of a sand dredged mound
    • Abstract: Publication date: August 2017
      Source:Coastal Engineering, Volume 126
      Author(s): Ernest R. Smith, Felice D'Alessandro, Giuseppe R. Tomasicchio, Joseph Z. Gailani
      As a part of the Dredging Operations and Environmental Research (DOER) Program, movable-bed physical model experiments were performed at the U.S. Army Engineer Research and Development Centre's (ERDC), Large-scale Sediment Transport Facility (LSTF) to investigate the fate and evaluate the benefits of nearshore-placed dredged material. The resulting bathymetry was measured with detailed surveys, the migration of the mound was quantified and comprehensive observations of hydrodynamics were obtained. The potential suitability of dredged material placement in the nearshore/surf zone was demonstrated after 10 h of oblique wave attacks. It has been shown that, as the mound was located at the edge of the surf zone, very likely wave breaking induced horizontal circulation may be dominant. A downdrift accretion of the submerged beach was observed, which is due to the transport of part of the sediment suspended by breakers at the mound and captured by the longshore currents. The experiments provided useful validation data for numerical morphological models.

      PubDate: 2017-06-06T11:59:12Z
       
  • Evaluation of XBeach performance for the erosion of a laboratory sand dune
    • Abstract: Publication date: July 2017
      Source:Coastal Engineering, Volume 125
      Author(s): Neville Anne Berard, Ryan Patrick Mulligan, Ana Maria Ferreira da Silva, Mohammad Dibajnia
      A new set of laboratory data is used to investigate the bathymetry change of a steep sand dune exposed to waves and high water levels, and subsequently compared to the results of numerical simulations using XBeach. Bichromatic wave boundary conditions are used to simulate a combined short-wave and long-wave field for two water level elevations corresponding to collision with the dune face, and overwashing of the dune crest. In the collision regime case, episodic slumping due to the undercutting of the dune results in sudden erosional events followed by long periods of wave-driven reshaping at the dune toe. In the overwash regime case, morphological changes are faster and sediment transport rates are higher. The XBeach model was used to simulate wave-driven erosion of the dune at the two water levels observed in the laboratory. The model was not able to precisely recreate the cross-shore spatial variability of significant wave height observed in the experiments, however near-bed wave-orbital and mean current velocities were in good agreement with observations. Following rapid initial adjustment, the model results were in agreement with measured dune morphology at successive times. XBeach was sensitive to several parameters that control the rate of erosion including the critical avalanching slope under water, the threshold water depth and the sediment transport formulation, and performed well after careful selection of the best combination of these parameters. Overall, the model predictions were in better agreement with laboratory observations for dune erosion in the overwash regime case than the collision regime case.

      PubDate: 2017-05-01T06:37:37Z
       
  • Application of a buoyancy-modified k-ω SST turbulence model to simulate
           
    • Abstract: Publication date: July 2017
      Source:Coastal Engineering, Volume 125
      Author(s): Brecht Devolder, Pieter Rauwoens, Peter Troch
      The objective of the present work is to investigate wave run-up around a monopile subjected to regular waves inside a numerical wave flume using the Computational Fluid Dynamics (CFD) toolbox OpenFOAM®. Reynolds-Averaged Navier-Stokes (RANS) turbulence modelling is performed by applying the k-ω SST model. Boundary conditions for wave generation and absorption are adopted from the IHFOAM toolbox. Simulations of propagating water waves show sometimes excessive wave damping (i.e. a significant decrease in wave height over the length of the numerical wave flume) based on RANS turbulence modelling. This anomaly is prevented by implementing a buoyancy term in the turbulent kinetic energy equation. The additional term suppresses the turbulence level at the interface between water and air. The proposed buoyancy-modified k-ω SST turbulence model results in an overall stable wave propagation model without significant wave damping over the length of the flume. Firstly, the necessity of a buoyancy-modified k-ω SST turbulence model is demonstrated for the case of propagating water waves in an empty wave flume. Secondly, numerical results of wave run-up around a monopile under regular waves using the buoyancy-modified k-ω SST turbulence model are validated by using experimental data measured in a wave flume by De Vos et al. (2007). Furthermore, time-dependent high spatial resolutions of the numerically obtained wave run-up around the monopile are presented. These results are in line with the experimental data and available analytical formulations.

      PubDate: 2017-05-01T06:37:37Z
       
  • Ripple and sandbar dynamics under mid-reflecting conditions with a porous
           vertical breakwater
    • Abstract: Publication date: July 2017
      Source:Coastal Engineering, Volume 125
      Author(s): M. Cobos, L. Chiapponi, S. Longo, A. Baquerizo, M.A. Losada
      This research is an experimental study of ripple and sandbar dynamics under regular and random waves in partially reflective conditions. As part of this study, a series of small-scale flume experiments were performed that reproduced the growth and migration of the bedforms, starting from a flat bed or rippled bed, with sediment transport in the bedload regime. The results showed that the evolution and dynamics of sandbar geometry were slower processes than the evolution of ripples. Moreover, they were governed by the wave field, reflective conditions, and sediment characteristics. Sandbar generation was controlled by the intensity of reflection, whereas the location of the crests (or deposition and erosion areas) was constrained by the phase shift of the reflected waves. Significant differences were also found between sandbars under regular and random waves. Sandbars under regular waves showed flat or practically flat troughs. In contrast, sandbars under random waves were almost uniformly covered by ripples. The experimental results showed that the concurrence of ripples and sandbars under partially reflected waves has a spatially modulating effect on ripple characteristics (i.e. growth, shape and migration celerity), which could not be consistently interpreted by using the classical formulas valid for ripples under progressive waves and/or without large-scale bedforms. This variability was more pronounced for regular waves than for random wave trains. Larger ripples develop in the nodes of the free surface envelope (more or less corresponding to the sandbars crests), whereas smaller ripples occurred in the antinodes (or sandbars troughs). The statistics of ripples geometry and celerity were computed with a sample stratification, based on their position in reference to the sandbars. In addition, they were compared in two energetically equivalent tests with regular and random waves, respectively. Although ripples under random waves had a larger wavelength and height than ripples under regular waves, the celerity of migration was comparable. Our results showed that the sandbars modified the equilibrium geometry of ripples. Furthermore, because of roughness, streaming was induced by the highest and longest ripples in the sandbar crests. The spatial modulation of the ripple celerity was found to be related to the local Lagrangian mass transport velocity, which was produced by the quasi-standing wave inside the bottom boundary layer at the grain-diameter scale.

      PubDate: 2017-05-01T06:37:37Z
       
  • Numerical investigation of transient harbor oscillations induced by
           N-waves
    • Abstract: Publication date: Available online 25 April 2017
      Source:Coastal Engineering
      Author(s): Junliang Gao, Chunyan Ji, Oleg Gaidai, Yingyi Liu, Xiaojian Ma
      Tsunamis are traveling waves characterized by large amplitudes and long wavelengths close to the coastline. Often, the first couple of leading waves are either leading-elevation N-waves (LEN waves) or leading-depression N-waves (LDN waves). These waves are usually devastating, causing serious damage to coastal infrastructures or even human casualties. Among various natural disasters related to tsunamis, harbor oscillations are one of the most frequent disasters around the world, which can cause excessive movements of moored ships and rupture mooring lines inside the harbor. In this article, transient harbor oscillations induced by various incident N-waves are first investigated. The transient oscillations are simulated by a fully nonlinear Boussinesq model, FUNWAVE-TVD. The incident N-waves include the TS-type and MS-type isosceles LEN and LDN waves. The TS- and MS-type N-waves correspond to the waveform expressions proposed by Tadepalli and Synolakis [1] and Madsen and Schäffer [2], respectively. This paper focuses on the effects of the incident wave amplitude and its type on the relative wave energy distribution inside the harbor. The maximum runup and rundown of various incident waves are also discussed. For comparison, the transient oscillations excited by solitary waves are also considered. The harbor used in this paper is assumed to be long and narrow and has constant depth; the free surface movement inside the harbor is essentially one-dimensional. This study reveals that, for the given harbor, for the range of the incident wave amplitude and the incident wave types studied in this paper, the larger tsunamis lead to a more uniform relative wave energy distribution inside the harbor. The relative wave energy distributions induced by the LDN waves are always more uniform than those induced by the LEN waves, while the relative wave energy distributions induced by the solitary waves are more concentrated than those induced by the various N-waves. When the incident wave amplitude is relatively large, the maximum runups of the LDN waves are considerably larger than those of the solitary waves, while those of the LEN waves are much less than those of the solitary waves.

      PubDate: 2017-05-01T06:37:37Z
       
  • Evaluation of surface wind fields for prediction of directional ocean wave
           spectra during Hurricane Sandy
    • Abstract: Publication date: July 2017
      Source:Coastal Engineering, Volume 125
      Author(s): Vanessa C.C. Bennett, Ryan P. Mulligan
      Hurricane Sandy was the largest storm on historical record in the Atlantic Ocean basin with extensive coastal damage caused by large waves and high storm surge. In this study, three different spatially-varying surface wind and atmospheric pressure fields that are used for forecasting or hindcasting hurricane waves on the continental shelf are investigated. These wind fields include two 2D parametric wind models (Holland model, H80; Generalized Asymmetric Holland Model, GAHM), and a 3D atmospheric model with data assimilation (WeatherFlow Regional Atmospheric Modelling System, WRAMS). These wind fields are used to drive wave hindcasts using coupled Delft3D-SWAN hydrodynamic and ocean wave models on a regional grid, and the bulk wave statistics and the directional wave spectra are compared to observations at offshore wave buoys to investigate the impact of differences between the complex wind fields on predictions of the sea surface evolution. The spatial and temporal distribution of bulk wave parameters are different for each wind field. The WRAMS wind field produces wave model predictions in the best agreement with significant wave height observations, followed by the GAHM and H80 wind fields, with mean correlation coefficients of 0.91, 0.82 and 0.75, respectively averaged over 9 sites. The directional wave spectra for Hurricane Sandy was bi-modal predominantly in the two left quadrants of the hurricane, in agreement with buoy observations. The results indicate that a regional atmospheric wind model that has the best description of the wind field is the most appropriate forcing for hindcasting hurricane waves when detailed observations are available. However a parametric vortex model that incorporates wind at multiple isotachs results in very good agreement with wave observations when used in the wave model, and is a useful too for forecasting hurricane sea surface conditions. The results of this study are relevant for other tropical cyclones that undergo extratropical transition or are influenced by other atmospheric disturbances at mid-latitudes, resulting in storms with large spatial size and high asymmetry.

      PubDate: 2017-04-24T06:14:36Z
       
  • On the transfer of momentum from a granular landslide to a water wave
    • Abstract: Publication date: July 2017
      Source:Coastal Engineering, Volume 125
      Author(s): Ryan P. Mulligan, W. Andy Take
      The momentum flux from a landslide at impact in a water body is the driving force behind the generation of landslide tsunamis. Analysis of this problem is presented and used to derive idealized theoretical relationships for the maximum wave amplitude in the near-field zone. This is accomplished for momentum transfer using both hydrostatic and hydrodynamic assumptions. For rapidly evolving near-field waves with a supercritical densimetric Froude number, the maximum wave amplitude is also constrained according to the fluid continuity equation. Simplification of the hydrostatic momentum equation is also presented by considering fluid acceleration, resulting in an expression that is independent of length and time scales during wave generation. The results of the novel momentum-based equations are in agreement with laboratory data collected using high-speed digital cameras for granular landslides and previously published experimental data used to develop a semi-empirical equation. Furthermore, the results provide new insight on the range of applicability of theoretical and semi-empirical equations for predicting the maximum near-field wave amplitude of landslide-generated tsunamis.

      PubDate: 2017-04-24T06:14:36Z
       
  • Flow separation effects on shoreline sediment transport
    • Abstract: Publication date: July 2017
      Source:Coastal Engineering, Volume 125
      Author(s): Julia Hopkins, Steve Elgar, Britt Raubenheimer
      Field-tested numerical model simulations are used to estimate the effects of an inlet, ebb shoal, wave height, wave direction, and shoreline geometry on the variability of bathymetric change on a curved coast with a migrating inlet and strong nearshore currents. The model uses bathymetry measured along the southern shoreline of Martha's Vineyard, MA, and was validated with waves and currents observed from the shoreline to ~10-m water depth. Between 2007 and 2014, the inlet was open and the shoreline along the southeast corner of the island eroded ~200m and became sharper. Between 2014 and 2015, the corner accreted and became smoother as the inlet closed. Numerical simulations indicate that variability of sediment transport near the corner shoreline depends more strongly on its radius of curvature (a proxy for the separation of tidal flows from the coast) than on the presence of the inlet, the ebb shoal, or wave height and direction. As the radius of curvature decreases (as the corner sharpens), tidal asymmetry of nearshore currents is enhanced, leading to more sediment transport near the shoreline over several tidal cycles. The results suggest that feedbacks between shoreline geometry and inner-shelf flows can be important to coastal erosion and accretion in the vicinity of an inlet.

      PubDate: 2017-04-24T06:14:36Z
       
  • Calibrating and assessing uncertainty in coastal numerical models
    • Abstract: Publication date: July 2017
      Source:Coastal Engineering, Volume 125
      Author(s): Joshua A. Simmons, Mitchell D. Harley, Lucy A. Marshall, Ian L. Turner, Kristen D. Splinter, Ronald J. Cox
      Advanced numerical models used to predict coastal change at a variety of time and spatial scales often contain many free parameters that require calibration to the available field data. At present, little guidance (beyond the adoption of the default values provided) is available in the field of coastal engineering to inform the selection of best-fit parameter values. Common calibration techniques can often lack a rigorous quantification of model sensitivity to parameters and parameter-induced model uncertainty. Here we employ the Generalised Likelihood Uncertainty Estimation (GLUE) method to address these issues. The GLUE method uses Monte Carlo sampling to assess the skill of many different combinations of model parameters when compared to observational data. As a rigorous modelling framework, the GLUE method provides a series of standard tools that assist the modeller to analyse model sensitivity, undertake parameter optimisation and quantify parameter-induced uncertainty. In addition, new tools are presented here to identify where unique calibrated parameter sets are required for different observational data (e.g., should the calibrated parameter set differ between alongshore locations at a site) and investigate the convergence of GLUE estimated optimum parameter values over increasing numbers of Monte Carlo samples. As the methodology and philosophy of GLUE is well established in other fields, this paper presents a practical case study to explore the strengths and weaknesses of the method when applied to a relatively complex coastal numerical model (XBeach). The results obtained are compared to a previously reported and more ‘standard’ model calibration undertaken within the context of a coastal storm early warning system. While the GLUE method requires orders of magnitude more computational power, it is shown that its use in place of the more common one-at-a-time ‘trial-and-error’ approach to model calibration, provides: a significant improvement in predictive skill; a more rigorous evaluation of the model sensitivity to parameters; the ability to identify distinct differences in the XBeach model performance dependent on dune impact processes; and additional analysis including the quantification of parameter-induced uncertainty.

      PubDate: 2017-04-24T06:14:36Z
       
  • Applying a Bayesian network based on Gaussian copulas to model the
           hydraulic boundary conditions for hurricane flood risk analysis in a
           coastal watershed
    • Abstract: Publication date: July 2017
      Source:Coastal Engineering, Volume 125
      Author(s): A. Sebastian, E.J.C. Dupuits, O. Morales-Nápoles
      In recent years significant emphasis has been placed on quantifying coastal flood hazards in the U.S. using high resolution 2-D hydrodynamic and nearshore wave models. However, these studies are computationally expensive and often neglect to consider the flooding that arises from the combined hazards of precipitation and storm surge in coastal watersheds. This paper describes a method to stochastically simulate a large number of combinations of peak storm surge and cumulative precipitation to determine the hydraulic boundary conditions for a low-lying coastal watershed draining into a semi-enclosed tidal bay. The method is computationally efficient and takes into consideration five tropical cyclone characteristics at landfall: windspeed, angle of approach, landfall location, radius of maximum winds, and forward speed. A precipitation gage network and tidal gage data were used, along with observations from over 300 tropical cyclones in the Gulf of Mexico. A Non-parametric Bayesian Network was built to generate 100,000 synthetic storm events and used as input to an empirical wind set-up model to simulate storm surge within a tidal bay and at the downstream boundary of the watershed. Based on the results, probable combinations of cumulative precipitation and peak storm surge for the watershed during hurricane conditions are determined. These boundary conditions can be easily incorporated into a coastal riverine model to determine flood risk in the watershed.

      PubDate: 2017-04-24T06:14:36Z
       
  • Suspended sediment transport around a large-scale laboratory breaker bar
    • Abstract: Publication date: July 2017
      Source:Coastal Engineering, Volume 125
      Author(s): J. van der Zanden, D.A. van der A, D. Hurther, I. Cáceres, T. O’Donoghue, J.S. Ribberink
      This paper presents novel insights into suspended sediment concentrations and fluxes under a large-scale laboratory plunging wave. Measurements of sediment concentrations and velocities were taken at 12 locations around an evolving breaker bar, covering the complete breaking region from shoaling to inner surf zone, with particular high resolution near the bed using an Acoustic Concentration and Velocity Profiler. Wave breaking evidently affects sediment pick-up rates, which increase by an order of magnitude from shoaling to breaking zone. Time-averaged reference concentrations correlate poorly with periodic and time-averaged near-bed velocities, but correlate significantly with near-bed time-averaged turbulent kinetic energy. The net depth-integrated suspended transport is offshore-directed and primarily attributed to current-related fluxes (undertow) at outer-flow elevations (i.e. above the wave bottom boundary layer). The wave-related suspended transport is onshore-directed and is generally confined to the wave bottom boundary layer. Cross-shore gradients of sediment fluxes are quantified to explain spatial patterns of sediment pick-up and deposition and of cross-shore sediment advection. Suspended particles travel back and forth between the breaking and shoaling zones following the orbital motion, leading to local intra-wave concentration changes. At locations between the breaker bar crest and bar trough, intra-wave concentration changes are due to a combination of horizontal advection and of vertical exchange with the bedload layer: sediment is entrained in the bar trough during the wave trough phase, almost instantly advected offshore, and deposited near the bar crest during the wave crest phase. Finally, these results are used to suggest improvements for suspended sediment transport models.

      PubDate: 2017-04-24T06:14:36Z
       
  • Design requirement for mixed sand and gravel beach defences under
           scenarios of sea level rise
    • Abstract: Publication date: June 2017
      Source:Coastal Engineering, Volume 124
      Author(s): Uwe Dornbusch
      Along many coastlines of the world, beaches provide the primary defence against flooding or erosion with their fate under rising sea levels still only poorly researched. This is particularly the case for the coastline of Southeast England, where ~190km of shingle barriers protect low-lying hinterland or a coastal plain that is at or barely above the present reach of waves. During the Holocene transgression, these beaches moved into their present position through longshore extension and cross-shore roll back. This process stopped more than a century ago with port developments affecting longshore transport and the construction of groynes to hold the beach in place. This was followed by beach recharge and recycling towards the end of the 20th century to build up and maintain beaches as coastal defences in their mid 19th century position. This paper explores the design requirements for these beaches under future sea level rise scenarios of 1 to 5m using recently developed tools. It shows that the presently still semi-natural beaches have to increase in size with crest height elevations having to rise by at least up to 1.26 times the rate of sea level rise and that due to higher longshore wave power, especially during storm conditions in the future, higher and stronger groynes are needed to hold these larger beaches in place. Future design requirements for beaches are sensitive to foreshore levels and orientation of the beach to the dominant waves with those presently characterised by shallow foreshores and oblique wave approach requiring the biggest adjustments. Required size increases will be difficult to implement due to the built-up nature of the hinterland. The engineering alternative would be to replace beaches with hard structures, a process that has already started where maintaining a beach is no longer economically viable or the residual risk associated with overwashing and an eventual tidal breach has become unacceptable.

      PubDate: 2017-04-17T11:38:28Z
       
  • GOW2: A global wave hindcast for coastal applications
    • Abstract: Publication date: June 2017
      Source:Coastal Engineering, Volume 124
      Author(s): Jorge Perez, Melisa Menendez, Inigo J. Losada
      Global wave hindcasts provide wave climate information for long time periods which helps to improve our understanding of climate variability, long term trends and extremes. This information is extremely useful for coastal studies and can be used both directly or as boundary conditions for regional and local downscalings. This work presents the GOW2 database, a long-term wave hindcast covering the world coastline with improved resolution in coastal areas and along ocean islands. For developing the GOW2 hindcast, WAVEWATCH III wave model is used in a multigrid two-way nesting configuration from 1979 onwards. The multigrid includes a global grid of half degree spatial resolution, specific grids configured for the Arctic and the Antarctic polar areas, and a grid of higher resolution (about 25km) for all the coastal locations at a depth shallower than 200m. Available outputs include hourly sea state parameters (e.g. significant wave height, peak period, mean wave direction) and series of 3-h spectra at more than 40000 locations in coastal areas. Comparisons with instrumental data show a clear improvement with respect to existing global hindcasts, especially in semi-enclosed basins and areas with a complex bathymetry. The effect of tropical cyclones is also well-captured thanks to the high resolution of the forcings and the wave model setup. The new database shows a high potential for a variety of applications in coastal engineering.

      PubDate: 2017-04-10T11:31:01Z
       
  • Deriving environmental contours from highest density regions
    • Abstract: Publication date: May 2017
      Source:Coastal Engineering, Volume 123
      Author(s): Andreas F. Haselsteiner, Jan-Hendrik Ohlendorf, Werner Wosniok, Klaus-Dieter Thoben
      Environmental contours are an established method in probabilistic engineering design, especially in ocean engineering. The contours help engineers to select the environmental states which are appropriate for structural design calculations. Defining an environmental contour means enclosing a region in the variable space which corresponds to a certain return period. However, there are multiple definitions of environmental contours for a given return period as well as different methods to compute a contour. Here, we analyze the established approaches and present a new concept which we call highest density contour (HDC). We define this environmental contour to enclose the highest density region (HDR) of a given probability density. This region occupies the smallest possible volume in the variable space among all regions with the same included probability, which is advantageous for engineering design. We perform the calculations using a numerical grid to discretize the original variable space into a finite number of grid cells. Each cell's probability is estimated and used for numerical integration. The proposed method can be applied to any number of dimensions, i.e. number of different variables in the joint probability model. To put the highest density contour method in context, we compare it to the established inverse first-order reliability method (IFORM) and show that for common probability distributions the two methods yield similarly shaped contours. In multimodal probability distributions, however, where IFORM leads to contours which are difficult to interpret, the presented method still generates clearly defined contours.

      PubDate: 2017-04-10T11:31:01Z
       
  • Impulse waves in reservoirs generated by landslides into shallow water
    • Abstract: Publication date: May 2017
      Source:Coastal Engineering, Volume 123
      Author(s): Bolin Huang, S.C. Wang, Y.B. Zhao
      Landslides sliding into shallow water often block watercourses, and in addition landslide-induced impulse waves may result in risks to the safety of the reservoir or waterways over a wide area. Such impulse waves differ from those from landslides into deep water which slide underwater completely. This study conducted twenty-five groups of orthogonal experiments of landslide-induced impulse waves in shallow water where the Froude numbers ranged between 0.6 and 2.0. Based on the experimental results, dimensionless functions of the parameters such as amplitude, wavelength and jet-flow height of the initial landslide-induced waves in shallow water were derived. The predictions from these formulae are very close to those obtained from the experiments. Further, a source model of landslide-induced waves in shallow water was built based on formulae derived from the experiments, and wave propagation and run-up were calculated with the Boussinesq-type equations model. The newly built model of landslide-induced waves in shallow water was used to calculate and analyze two representative examples from landslides in the Three Gorges in China, namely the Qianjiangping landslide-induced impulse wave event and the Xintan landslide-induced impulse wave event. Comparison of the calculations with data from multiple sources indicated that our model for landslide-induced waves in shallow water had high accuracy. Our model for landslide-induced waves in shallow water may help in the predictive analysis of impulse waves and mitigation works for this type of event in reservoirs worldwide.

      PubDate: 2017-04-10T11:31:01Z
       
  • Aeolian sediment supply at a mega nourishment
    • Abstract: Publication date: May 2017
      Source:Coastal Engineering, Volume 123
      Author(s): Bas Hoonhout, Sierd de Vries
      Mega nourishments are intended to enhance growth and resilience of coastal dunes on medium to long time scales by stimulation of natural sediment transport processes. The growth and resilience of coastal dunes largely depends on the presence of a continuous supply of aeolian sediment. A recent example of a mega nourishment is the 21Mm3 mega nourishment known as the Sand Motor. The Sand Motor is intended to nourish the entire Holland coast over a period of two decades. Four years of bi-monthly topographic measurements of the Sand Motor domain provide an opportunity to analyze spatiotemporal variations in aeolian sediment supply using an aeolian sediment budget analysis. It appears that more than 58% of all aeolian sediment deposits originate from the low-lying beaches that are regularly reworked by waves. Aeolian sediment supply from higher beaches diminished after half a year after construction of the Sand Motor, likely due to the formation of deflation lag deposits that constitute a beach armor layer. The compartmentalization of the Sand Motor in armored and unarmored surfaces suggests that the construction height is an important design criterion that influences the lifetime and region of influence for any mega nourishment.

      PubDate: 2017-04-03T08:15:27Z
       
  • Prediction formula for the spectral wave period Tm-1,0 on mildly sloping
           shallow foreshores
    • Abstract: Publication date: May 2017
      Source:Coastal Engineering, Volume 123
      Author(s): Bas Hofland, Xuexue Chen, Corrado Altomare, Patrick Oosterlo
      During the last decades, the spectral wave period T m-1,0 has become accepted as a characteristic wave period when describing the hydraulic attack on coastal structures, especially over shallow foreshores. In this study, we derive an empirical prediction formula for T m-1,0 on shallow to extremely shallow foreshores with a mild slope. The formula was determined based on flume tests and numerical calculations, mainly for straight linear foreshore slopes. It is shown that the wave period increases drastically when the water depth decreases; up to eight times the offshore value. The bed slope angle influences the wave period slightly. For short-crested wave fields, the strong increase of T m-1,0 starts closer to shore (at smaller water depths) than for long-crested wave fields.

      PubDate: 2017-04-03T08:15:27Z
       
  • Simulating wave setup and runup during storm conditions on a complex
           barred beach
    • Abstract: Publication date: May 2017
      Source:Coastal Engineering, Volume 123
      Author(s): Alexandre Nicolae Lerma, Rodrigo Pedreros, Arthur Robinet, Nadia Sénéchal
      The purpose of this study is to assess the ability of the SWASH model to reproduce wave setup and runup in highly dissipative stormy conditions. To proceed we use data collected during the ECORS Truc Vert’08 Experiment, especially during the Johanna storm in the winter of 2007-008 (wave setup under H s= 8.2m and T p= 18.3s and runup under 6.4m and peak period up to 16.4s). We test different model settings (1D and 2D mode) and model forcing (spectral and parametric) to reproduce sensor measured wave setup at several locations in the nearshore area and video measured runup on two beach profiles. For the whole tested configurations, the wave setup is reproduced accurately. Results considering all the sensor locations in the near shore area in 1D and 2D are significantly correlated to the observations with respectively ρ ² =0.66 and 0.81; RMSE=0.13m and 0.08m without any significant bias. Observations and simulations of runup are investigated in terms of spectra and statistic component. 1D simulations produces an overall overestimation and no significant improvement is obtained by modifying the breaking parameters. The results for 2D simulations are fairly satisfactory reproducing significant swash height (S), but are significantly improved with spectral forcing than parametric with respectively ρ ² =0.73 and 0.71, RMSE=0.19m and 0.43m. Generally, the model reproduces accurately the infragravity component but tends to overestimate the incident component, leading to an overestimation of the energy density for moderate wave conditions and more accurate results for higher-energy wave conditions. Results in 2D with spectral forcing show a saturation of the infragravity component with a threshold around H s=4 to 5m, which is comparable to the observations collected at Truc Vert Beach. As regards the conventional statistical parameter for runup estimation (R 2%) three methods are applied to derive the 2% exceedence value for runup from observed and simulated shoreline vertical elevation time series. When R 2% is based on the sum of wave setup and half of the significant swash height, results provided by the model are close or even better than estimations provided by empirical formulas from the bibliography. Defining R2% as the exceeded 2% values of the time, derived considering the cumulative distribution function of the entire water-level time series also provide fairly good results. Results using only runup maxima time series are less satisfactory. In the two last cases, R 2% is slightly underestimated for moderate wave conditions (H s<4m; T p ≈ 14s) and overestimated for higher-energy wave conditions. Generally results shows that where extreme wave conditions are concerned, the model setting must be considered carefully because the simplification of 1D (rather than 2D), or the use of parametric wave description (rather than spectral), can be a source of significant inaccuracy or overestimation in simulated run-up values.

      PubDate: 2017-04-03T08:15:27Z
       
  • Periodic water waves through a heterogeneous coastal forest of arbitrary
           shape
    • Abstract: Publication date: April 2017
      Source:Coastal Engineering, Volume 122
      Author(s): Che-Wei Chang, Philip L.-F. Liu, Chiang C. Mei, Maria Maza
      Small-amplitude water waves propagating through a heterogeneous coastal forest of arbitrary shape is studied. Following the theoretical approach introduced by Liu et al. [10], the forest is modeled by an array of rigid and vertical cylinders. Assuming that the wavelength is much larger than the cylinder diameter and the cylinder spacing, a multi-scale perturbation theory of homogenization ([15]) is applied to separate the micro-scale flow problem within a unit cell, containing one or more cylinders, from the macro-scale wave dynamics. The complex coefficients in the derived macro-scale governing equations are computed from the solutions of micro-scale problem, in which the macro-scale pressure gradients are the driven force. The boundary integral equation method is employed to solve the macro-scale wave dynamic problem where the forest has an arbitrary shape and is composed of multiple forest patches. Each forest patch can be divided into subzones according to different forest properties, such as the porosity and cylinder diameter. Each subzone is considered as a homogeneous forest region with a constant bulk eddy viscosity, which is determined by invoking the balance of the time-averaged dissipation rate and the rate of work done by wave forces. A computing program has been developed based on the present approach. The numerical model is checked with existing theoretical works and laboratory experiments. The numerical solutions compare almost perfectly with the semi-analytical solutions for a single circular forest reported in Liu et al. [10]. The numerical model is then applied to cases where the forest region is made of multiple circular patches. Experimental data for these cases ([12,14]) is used to validate the numerical results. The comparison between model predictions and the experimental data is in reasonable agreement. The effectiveness of these two special forest configurations on wave attenuation is also discussed.

      PubDate: 2017-03-27T09:17:59Z
       
  • An experimental method to verify the failure of coastal structures by wave
           induced liquefaction of clayey soils
    • Abstract: Publication date: May 2017
      Source:Coastal Engineering, Volume 123
      Author(s): Valeria Chávez, Edgar Mendoza, Rodolfo Silva, Anahí Silva, Miguel A. Losada
      Although the dynamics involved in the liquefaction process are understood reasonably well, experimental work to reproduce the sinking of structures due to liquefaction, which is representative and repeatable, has so far not been recorded. In this work, three sets of experiments were performed in an attempt to fill the gaps in the knowledge by modelling a small scale reproduction of the failure. Firstly, an analysis of the role of the proportions of the initial fine sediment and water content is presented; secondly, a group of tests involving a vertical breakwater were performed, and thirdly, an experiment was carried out to reproduce the failure of a submerged structure on a clayey bed in the presence of waves. From these experiments, we were able to set thresholds for bed composition, below which soil liquefaction is likely to occur. It was determined that the potential to liquefy increases with the initial water content and that soils of 40% or more clay content may liquefy. This methodology has proven to be repeatable, allowing the reproduction of the sinking of coastal structures due to liquefaction of the underlying soil.

      PubDate: 2017-03-08T02:34:38Z
       
  • Modeling transient long waves propagating through a heterogeneous coastal
           forest of arbitrary shape
    • Abstract: Publication date: April 2017
      Source:Coastal Engineering, Volume 122
      Author(s): Che-Wei Chang, Philip L.-F. Liu, Chiang C. Mei, Maria Maza
      A model is proposed to study transient long waves propagating through coastal vegetation. The coastal forest is modeled by an array of rigid and vertically surface-piercing cylinders. The homogenization method, i.e. multi-scale perturbation theory, is applied to separate two contrasting physical length scales: the scale characterizing transient waves and the scale representing the diameter of and the spacing among cylinders. Fourier transform is employed so that the free surface elevation and velocity field are solved in the frequency domain. For each harmonic, the flow motion within a unit cell, consisting of one or more cylinders, is obtained by solving the micro-scale boundary-value problem, which is driven by the macro-scale (wavelength scale) pressure gradients. The cell-averaged equations governing the macro-scale wave amplitude spectrum are derived with the consideration of the effects of the cell problem solution. Similar to [1], the macro-scale wave amplitude spectrum is solved numerically with the boundary integral equation method, where a vegetated area is composed of multiple patches of arbitrary shape. Each forest patch can be divided into subzones according to different properties, such as planting pattern and vegetation size. Each subzone is considered as a homogeneous forest region with a constant bulk eddy viscosity determined by the empirical formula suggested in [13]. Once the solutions for wave amplitude spectrum are obtained, the free surface elevation can then be computed from the inverse Fourier transform. A computing program is developed based on the present numerical model. To check the present approach, we investigate several different forest configurations. However, we focus on incident waves with a soliton-like shape. We first re-examine the forest belt case. The numerical model is then checked by available theoretical results along with experimental measurements for two special forest configurations. For a single circular forest, the numerical results compare almost perfectly with the analytical solutions. The comparison with experimental data also shows very good agreements. The effects of different wave parameters on damping rate are discussed. The numerical model is further compared with the experiments for a forest region consisting of multiple circular patches. Good agreements are also observed between the simulated free surface elevations and the experimental measurements. The effectiveness of these two forest configurations on wave attenuation is discussed.

      PubDate: 2017-03-02T02:29:32Z
       
  • An event-based approach for extreme joint probabilities of waves and sea
           levels
    • Abstract: Publication date: April 2017
      Source:Coastal Engineering, Volume 122
      Author(s): Franck Mazas, Luc Hamm
      A methodology for determining extreme joint probabilities of two metocean variables, in particular wave height and sea level, is presented in the paper. This methodology focuses in particular on the sampling of the time series, which should be based on the notion of event: either the event generating the variables whose joint probabilities are wanted (such as a storm generating waves and surges) or the event that is a result of the combination of these variables (such as a beach erosion event generated by waves at high sea level). A classification is proposed for multivariate analyses in order to help the choice of the sampling method. The dependence between the variables is analysed using tools such as the chi-plot, of which an enhanced presentation is proposed, then is modelled by extreme-value copulas (Gumbel-Hougaard, Galambos and Hüsler-Reiss) estimated by Canonical Maximum Likelihood or by the upper tail dependence coefficient. Joint return periods are then computed. A comparison is made with a simulation from the JOIN-SEA software on a dataset of wave height and sea levels offshore Brest, France. Then the bivariate methodology is extended to a multivariate framework. The distribution of sea level is determined by an indirect approach (extrapolation of extreme surges then convolution with the astronomical tide) and the dependence is analysed between the wave height and the surge component only. A bidimensional convolution between the joint distribution of wave height and surge and the distribution of the astronomical tide yields the joint distribution of wave height and sea level. The application of this method to the dataset of Brest and its comparison with the bivariate approach are finally discussed.

      PubDate: 2017-02-22T18:43:15Z
       
  • Wave loadings acting on innovative rubble mound breakwater for overtopping
           wave energy conversion
    • Abstract: Publication date: April 2017
      Source:Coastal Engineering, Volume 122
      Author(s): Pasquale Contestabile, Claudio Iuppa, Enrico Di Lauro, Luca Cavallaro, Thomas Lykke Andersen, Diego Vicinanza
      The Overtopping BReakwater for Energy Conversion (OBREC) is an overtopping type wave energy converter, totally embedded into traditional rubble mound breakwaters. The device consists of a reinforced concrete front reservoir designed with the aim of capturing the wave overtopping in order to produce electricity. The energy is extracted through low head turbines, using the difference between the water levels in the reservoir and the sea water level. This paper investigates the nature and magnitude of wave loadings exerting on various parts of the structure. The results improve the overall knowledge on the device behavior, completing the highlights from the complementary test campaign carried out in the same wave flume in 2012 (Vicinanza et al., 2014). The formulas provided have been used to design the first OBREC prototype breakwater in operation since January 2016 at Naples Harbour (Italy).

      PubDate: 2017-02-22T18:43:15Z
       
  • A Boussinesq type extension of the GeoClaw model - a study of wave
           breaking phenomena applying dispersive long wave models
    • Abstract: Publication date: April 2017
      Source:Coastal Engineering, Volume 122
      Author(s): Jihwan Kim, Geir K. Pedersen, Finn Løvholt, Randall J. LeVeque
      The nonlinear shallow water model is widely used in the study of tsunami propagation, but an increasing number of studies are dedicated to the dispersion dynamics of tsunamis. If the wave dispersion becomes important, Boussinesq-type models are often used. In this work, a general purpose Boussinesq solver, BoussClaw, is introduced for modeling non-linear dispersive tsunami propagation, taking into account inundation. The BoussClaw model is an extension of the GeoClaw tsunami model. It employs a hybrid of finite volume and finite difference methods to solve Boussinesq equations from the literature, which are based on the depth-averaged velocity and include enhanced dispersion properties. On the other hand, in the selected formulation only some non-linearity is retained in the dispersion term. In order to validate BoussClaw, numerical results are compared to analytic solutions, solutions obtained by pre-existing models, and laboratory experiments. Even though the equations of BoussClaw are not fully nonlinear they perform far better than standard Boussinesq equations with only linear dispersion terms. Furthermore, the wave steepening and breaking are carefully scrutinized, and we demonstrate that the point of wave breaking may be wrongly identified in many of the commonly used Boussinesq models.

      PubDate: 2017-02-22T18:43:15Z
       
  • Numerical simulation of scour and backfilling processes around a circular
           pile in waves
    • Abstract: Publication date: April 2017
      Source:Coastal Engineering, Volume 122
      Author(s): C. Baykal, B.M. Sumer, D.R. Fuhrman, N.G. Jacobsen, J. Fredsøe
      This study continues the investigation of flow and scour around a vertical pile, reported by Roulund et al. (2005). Flow and scour/backfilling around a vertical pile exposed to waves are investigated by using a three-dimensional numerical model based on incompressible Reynolds averaged Navier–Stokes equations. The model incorporates (1) k-ω turbulence closure, (2) vortex shedding processes, (3) sediment transport (both bed and suspended load), as well as (4) bed morphology. The numerical simulations are carried out for a selected set of test conditions of the laboratory experiments of Sumer et al. (1997, 2013a), and the numerical results are compared with those of the latter experiments. The simulations are carried out for two kinds of beds: rigid bed, and sediment bed. The rigid-bed simulations indicate that the vortex shedding for waves around the pile occurs in a “one-cell” fashion with a uniform shedding frequency over the height of the cylinder, unlike the case for steady current where a two-cell structure prevails. The rigid-bed simulations further show that the horseshoe vortex flow also undergoes substantial changes in waves. The amplification of the bed shear stress around the pile (including the areas under the horseshoe vortex and the lee wake region) is obtained for various values of the Keulegan-Carpenter number, the principal parameter governing the flow around the pile in waves. The present model incorporated with the morphology component is applied to several scenarios of scour and backfilling around a pile exposed to waves. In the backfilling simulations, the initial scour hole is generated either by a steady current or by waves. The present simulations indicate that the scour and backfilling in waves are solely governed by the lee-wake flow, in agreement with observations. The numerical model has proven successful in predicting the backfilling of scour holes exposed to waves. The results of the numerical tests indicate that the equilibrium depth of scour holes is the same for both the scour and the backfilling for a given Keulegan-Carpenter number, in full agreement with observations.

      PubDate: 2017-02-22T18:43:15Z
       
  • Efficient and robust wave overtopping estimation for impermeable coastal
           structures in shallow foreshores using SWASH
    • Abstract: Publication date: April 2017
      Source:Coastal Engineering, Volume 122
      Author(s): Tomohiro Suzuki, Corrado Altomare, William Veale, Toon Verwaest, Koen Trouw, Peter Troch, Marcel Zijlema
      Estimation of wave overtopping over the crest of coastal structures is crucial to design effective and cost efficient countermeasures against storms. Semi-empirical formulas are often used for wave overtopping assessment, but they are not always applicable for complex structures which exist in reality (e.g. a storm wall on a dike in a shallow or very shallow foreshore). Detailed numerical models such as Eulerian and Lagrangian RANS models have potential to simulate overtopping of complex coastal structures with good accuracy. However such models require significant computational resources. The use of such models is often not feasible for the design of coastal structures, which often requires multiple iterations and model runs over a reasonably long period of time (e.g. wave trains with 1000 individual waves). In this paper we investigated the applicability of the simplified depth integrated wave transformation model SWASH for wave overtopping estimation of impermeable coastal structures in shallow foreshores. The validation results demonstrate the capability of SWASH to predict mean wave overtopping discharge with good accuracy compared to results from four different overtopping experimental campaigns (comprising 124 individual cases). The overall performance of SWASH to estimate mean wave overtopping discharge is as accurate as those obtained by semi-empirical equations in literature. However, in order to obtain accurate mean wave overtopping discharge with the SWASH model, the incident wave properties at the toe of the dike need to be accurately reproduced. For cases where this is not possible, a correction method is proposed in this paper. Detailed validation of the instantaneous wave overtopping also shows a good agreement with physical model data. In one example, a single, intensive overtopping event was not well resolved by the SWASH model and the instantaneous wave overtopping was under-predicted. However, this did not contribute significantly to the mean wave overtopping discharge. An additional advantage of the SWASH model is that specific coastal structure geometries can be modelled in SWASH if they are not covered by semi-empirical equations. Even in a case with rapidly varied flow (e.g. vertical wall on a dike) the model shows sufficient robustness. In this paper the details on the SWASH model configuration and post processing methods are outlined to enable the reader to reproduce reliable wave overtopping estimation over impermeable coastal structures in shallow foreshores.

      PubDate: 2017-02-22T18:43:15Z
       
  • Modelling of long waves generated by bottom-tilting wave maker
    • Abstract: Publication date: April 2017
      Source:Coastal Engineering, Volume 122
      Author(s): Heng Lu, Yong Sung Park, Yong-Sik Cho
      In order to generate very long waves in laboratory, a bottom-tilting wave maker is designed and used at the University of Dundee. This new type of wave maker can produce waves longer than solitary waves in terms of the effective wavelength, which provides better long wave model. Nonlinear and dispersive numerical models are built for modelling the wave tank. A shock-capturing finite volume scheme with high-order reconstruction method is used to solve the governing equations. By comparing to the experimental measurements, the numerical models are verified and able to approximate the resulting waves in the wave tank.

      PubDate: 2017-02-15T17:59:22Z
       
  • Comparison of inundation depth and momentum flux based fragilities for
           probabilistic tsunami damage assessment and uncertainty analysis
    • Abstract: Publication date: April 2017
      Source:Coastal Engineering, Volume 122
      Author(s): Hyoungsu Park, Daniel T. Cox, Andre R. Barbosa
      Annual exceedance probabilities of the maximum tsunami inundation depth, h Max , and momentum flux, M Max , conditional on a full-rupture event of the Cascadia Subduction Zone (CSZ) were used to estimate the probability of building damage using a fragility analysis at Seaside, Oregon. Tax lot data, Google Street View, and field reconnaissance surveys were used to classify the buildings in Seaside and to correlate building typologies with existing fragility curves according to the construction material, number of stories, and building seismic design level based on the date of construction. A fragility analysis was used to estimate the damage probability of buildings for 500-, 1000-, and 2500-year exceedance probabilities conditioned on a full-rupture CSZ event. Finally, the sensitivity of building damage was estimated for both the aleatory and epistemic uncertainties involved in the process of damage estimation. Probable damage estimates from the fragility curves based on h Max and on M Max both generally show higher damage probability for structures that are wooden and closer to the shoreline than those that are reinforced concrete (RC) and further landward of the shoreline. However, a relatively high and somewhat unrealistic damage probability was found at the river and creek region from the fragility curve analysis using h Max . Within 500m from the shoreline, wood structure damage shows significant sensitivity to the aleatory uncertainty of the tsunami generation from the CSZ event. On the other hand, RC structure damage showed equal sensitivity to the aleatory uncertainty of the tsunami generation as well as the epistemic uncertainties due to the numerical modeling of the tsunami inundation (friction), the building classification (material and date of construction), and the type of fragility curves (depth or momentum flux type curves). Further from the shoreline, the wood structures showed similar aleatory and epistemic uncertainties, qualitatively similar to the RC structure sensitivity closer to the shoreline.

      PubDate: 2017-02-15T17:59:22Z
       
  • The influence of swash-based reflection on surf zone hydrodynamics: a
           wave-by-wave approach
    • Abstract: Publication date: April 2017
      Source:Coastal Engineering, Volume 122
      Author(s): Kévin Martins, Chris E. Blenkinsopp, Rafael Almar, Jun Zang
      A detailed understanding of the behaviour of waves in the nearshore is essential for coastal engineers as these waves cause beach erosion, coastal flooding and damage to coastal structures. Significantly, the influence of reflected waves is often neglected in surf zone studies, although they are known to influence wave properties and circulation in the nearshore. In this paper, a phase-resolving model is rigorously applied to model conditions from the prototype-scale BARDEXII experiment in order to examine and assess the influence of swash-based reflection on surf zone hydrodynamics at both the individual wave and time-averaged timescales. Surface elevation is separated into incoming and outgoing signals using the Radon Transform and a crest tracking algorithm is used to extract incident and reflected wave properties. It is found that on steep beaches ( tan β > 1 : 9 ) the swash-based reflection - the reflection generated in the swash during the backwash - contributes significantly to the intrawave variability of individual wave properties such as the wave height to water depth ratio γ, through the generation of quasi-nodes/antinodes system. For γ expressed with individual wave heights, variations up to 25% and 40% are obtained for the modelled regular and irregular wave tests, whereas it reaches 15% when it is based on the significant wave height. The outgoing wave field-induced hydrodynamics is also found to affect time-averaged parameters: undertow and horizontal velocity skewness. The undertow is mainly strengthened, particularly in the shoaling region where the outgoing component dominates over the contribution from the incoming wave field. Offshore of the bar, an onshore-directed flow streaming close to the bed is also generated under the outgoing wave field, and is suspected to help in stabilising the bar position. This, along with the influence of the outgoing wave field on the horizontal velocity skewness and the presence of quasi-standing waves, suggests a complex contribution of the hydrodynamics induced by swash-based reflection into sediment transport rates and nearshore bar generation/migration.

      PubDate: 2017-02-15T17:59:22Z
       
  • The current generated by deep water regular waves
    • Abstract: Publication date: March 2017
      Source:Coastal Engineering, Volume 121
      Author(s): A.K. Bratland
      Second-order mean drift of wave particles can in deep water be calculated using potential theory, resulting in the well-known Stokes drift. Potential theory assumes an ideal, incompressible and irrotational flow, which according to Longuet-Higgins [8] is not permanent. In this document it is recommended, for rotational flow, to add a current term to Stokes wave equations. This is based on the argument that a change in wave number is due to the onset of a current.

      PubDate: 2017-01-14T11:55:02Z
       
  • Prediction of non-breaking wave induced scour depth at the trunk section
           of breakwaters using Genetic Programming and Artificial Neural Networks
    • Abstract: Publication date: March 2017
      Source:Coastal Engineering, Volume 121
      Author(s): Ali Pourzangbar, Miguel A. Losada, Aniseh Saber, Lida Rasoul Ahari, Philippe Larroudé, Mostafa Vaezi, Maurizio Brocchini
      Scour may act as a threat to coastal structures stability and reduce their functionality. Thus, protection against scour can guarantee these structures’ intended performance, which can be achieved by the accurate prediction of the maximum scour depth. Since the hydrodynamics of scour is very complex, existing formulas cannot produce good predictions. Therefore, in this paper, Genetic Programming (GP) and Artificial Neural Networks (ANNs) have been used to predict the maximum scour depth at breakwaters due to non-breaking waves ( S max / H n b ). The models have been built using the relative water depth at the toe ( h t o e / L n b ), the Shields parameter ( θ ), the non-breaking wave steepness ( H n b / L n b ), and the reflection coefficient ( C r ), where in the case of irregular waves, H nb =H rms , T nb =T peak and L nb is the wavelength associated with the peak period (L nb =L p ). 95 experimental datasets gathered from published literature on small-scale experiments have been used to develop the GP and ANNs models. The results indicate that the developed models perform significantly better than the empirical formulas derived from the mentioned experiments. The GP model is to be preferred, because it performed marginally better than the ANNs model and also produced an accurate and physically-sound equation for the prediction of the maximum scour depth. Furthermore, the average percentage change (APC) of input parameters in the GP and ANNs models shows that the maximum scour depth dependence on the reflection coefficient is larger than that of other input parameters.

      PubDate: 2017-01-14T11:55:02Z
       
  • Laboratory experiments on beach change due to nearshore mound placement
    • Abstract: Publication date: March 2017
      Source:Coastal Engineering, Volume 121
      Author(s): Ernest R. Smith, Michael C. Mohr, Shanon A. Chader
      Movable-bed large-scale laboratory experiments were conducted to examine the fate and quantify the benefits of nearshore placed dredged material. Two tests were performed on a beach classified as eroding [19] for mounds placed in the active zone described by Hands and Allison [12] at two depths. Mound sand was dyed to provide contrast and to differentiate it from the native sand beach. Beach surveys were performed intermittently during each experiment with a laser scanner. In addition to beach change elevations, the scanner provided RGB color components, which permitted tracking of the mound sand. The experiments showed that the mound sand dispersed rapidly and was transported mainly downdrift. Sand accumulation was observed on the beach onshore and adjacent to the mounds mainly due to wave sheltering of the mounds described as the longshore effect by [28]. There was little contribution to onshore accretion from cross-shore migration of the mounds. Beach response was similar to that of an offshore breakwater in which the mounds provided a wave shadow zone to the leeward beach. The results from the experiment will provide validation data for the numerical morphological model C2SHORE [15].

      PubDate: 2017-01-14T11:55:02Z
       
  • Entrained air in bore-driven swash on an impermeable rough slope
    • Abstract: Publication date: March 2017
      Source:Coastal Engineering, Volume 121
      Author(s): Han-Jing Dai, Gustaaf Adriaan Kikkert, Bo-Tao Chen, Dubravka Pokrajac
      The aim of the present investigation is to clarify the role and evaluate the importance of air entrainment in the swash zone by carrying out a set of detailed laboratory experiments. Experiments involved generating a single, highly repeatable, large-scale, bore-driven swash event on a sand-rough impermeable beach with slope 1:10. Measurements that yield the characteristics of the entrained air, including the void fractions, bubble size and bed-parallel bubble velocity, and the hydrodynamics are obtained at five cross-shore locations in the swash zone using an optical probe and a combined PIV/LIF system. The results show that two distinct bubble clouds enter the swash zone, the first is the result of local entrainment at the wave tip and the second are the remaining bubbles of the air that is entrained at the second plunge point of wave breaking before the wave starts climbing the beach. The void fractions are up to 0.20 and bubble size up to 20mm which are similar to air entrainment after wave breaking in the surf zone and deep water. Local entrainment of air continues in the swash zone, but void fractions decrease rapidly with distance up the slope and no air is present after flow reversal. Energy dissipation in the swash zone attributable to entrained air is at least of order 1% of the total energy dissipation. This is smaller than in the surf zone or deep water because of the smaller volume of entrained air and the greater total energy dissipation in the swash zone.

      PubDate: 2017-01-06T12:50:00Z
       
  • Optimisation of focused wave group runup on a plane beach
    • Abstract: Publication date: March 2017
      Source:Coastal Engineering, Volume 121
      Author(s): C.N. Whittaker, C.J. Fitzgerald, A.C. Raby, P.H. Taylor, J. Orszaghova, A.G.L. Borthwick
      Insight is provided into focused wave group runup on a plane beach by means of laboratory wave flume experiments and numerical simulations. A focused wave group is presented as an alternative to an empirical description of the wave conditions leading to extreme runup. Second-order correction to the laboratory wavemaker generation signal is observed to remove about 60% of the sub-harmonic error wave that would otherwise contaminate coastal response experiments. Laboratory measurements of the wave runup time history are obtained using inclined resistance-type wires and copper strips attached to the beach surface. The numerical wave runup model is based on hybrid Boussinesq-Nonlinear Shallow Water equations, empirical parameters for wave breaking and bed friction, and a wetting and drying algorithm. After calibration against experimental runup data, the numerical model reproduces satisfactorily the propagation, shoaling and runup of focused wave groups over the entire length of the wave flume. Results from a comprehensive parametric study show that both measured and predicted maximum runup elevations exhibit strong dependence on the linear focus amplitude of the wave group (linked to its probability of occurrence), the focus location, and the phase of the wave group at focus. The results also demonstrate that extreme runup events owing to focused wave incidence cannot be characterised using spectral parameters alone. The optimal band of focus locations shifts onshore as linear focus amplitude of the incident wave group increases. Optimisation of phase and focus location leads to a maximum runup elevation at each linear amplitude, and, when generated using second-order corrected paddle signals, the maximum runup appears to approach saturation at very large focused wave amplitudes. This study therefore moves beyond simple wave focusing, and presents a focused wave group as a tool for investigating the relationship between extremes within an incident wave field and extreme wave runup.

      PubDate: 2017-01-06T12:50:00Z
       
  • Measurements of suspended sediment transport and turbulent coherent
           structures induced by breaking waves using two-phase volumetric
           three-component velocimetry
    • Abstract: Publication date: March 2017
      Source:Coastal Engineering, Volume 121
      Author(s): Paul D. LeClaire, Francis C.K. Ting
      Sediment suspension and transport under plunging regular waves was investigated in a laboratory surf zone using the volumetric three-component velocimetry technique. The two-phase flow measurements captured the motions of sediment particles simultaneously with the three-component, three-dimensional velocity fields of turbulent coherent structures (large eddies) induced by plunging breakers. Sediment particles were separated from fluid tracers based on a combination of particle spot size and brightness in the two-phase flow images. The interactions between the large eddies and bottom sediment were investigated in the outer surf zone. The measured data showed that breaker vortices impinging on the bottom was the primary mechanism that lifted sediment particles into suspension. High suspended sediment concentrations were found in the wall-jet region where the impinging flow was deflected outward and upward. Sediment particles were also trapped by counter-rotating vortices behind the down flow. Suspended sediment concentrations were significantly lower in the impingement zone where the fluid velocities were downward, even though the turbulent kinetic energy in the down flow was very high. Suspended sediment concentration was well correlated with vertical velocity and apparent shear stresses in the deflected flow, and with vorticity magnitude in the counter-rotating vortices. A linear relationship was found between net sediment flux and net turbulent kinetic energy flux over one wave cycle. It was found that a strong deflected flow in front of the impingement zone enhanced onshore sediment transport compared to a more symmetrical flow pattern, while counter-rotating vortices kept sediment particles in suspension for transport offshore after flow reversal. Onshore sediment transport was observed in less than 20% of the breaking waves. In most wave cycles, net sediment flux was directed offshore due to advection by predominantly offshore flow velocities.

      PubDate: 2017-01-06T12:50:00Z
       
  • Improving the parameterization of wave nonlinearities – The importance
           of wave steepness, spectral bandwidth and beach slope
    • Abstract: Publication date: March 2017
      Source:Coastal Engineering, Volume 121
      Author(s): M.V.L. Rocha, H. Michallet, P.A. Silva
      Wave-velocity nonlinearities are among the main drivers of sediment transport. For practical engineering purposes, they can be described by simple parameterizations that allow their easier inclusion in nearshore morphodynamic models. Most existing parameterizations propose the estimation of velocity nonlinearities only from local wave parameters (such as the Ursell number). Herein, it is demonstrated that this provides inaccurate estimations of the wave nonlinearities. Furthermore, the effect of offshore wave steepness, offshore spectral bandwidth and beach slope on the velocity nonlinearities is shown to be sufficiently important to merit its inclusion in the existing parameterizations. Ruessink et al. (2012) [28] parameterization is modified in order to include both offshore spectral bandwidth and a new parameter, NP 0, which takes into account the beach slope and the squared offshore wave steepness. The new parameterization results in a reduction of the wave-nonlinearities estimation error of more than 50%, particularly for the maximum values of nonlinearity (near breaking) that contribute the most for sediment transport.

      PubDate: 2017-01-06T12:50:00Z
       
  • RANS-based simulation of wave-induced sheet-flow transport of graded
           sediments
    • Abstract: Publication date: March 2017
      Source:Coastal Engineering, Volume 121
      Author(s): Ugur Caliskan, David R. Fuhrman
      A one-dimensional vertical (1DV) turbulence-closure flow model, coupled with sediment transport capabilities, is extended to incorporate graded sediment mixtures. The hydrodynamic model solves the horizontal component of the incompressible Reynolds-averaged Navier–Stokes (RANS) equations coupled with k–ω turbulence closure. The sediment transport description includes both bed and suspended load descriptions. So-called high-concentration effects (turbulence damping and hindered settling velocities) are likewise included. The sediment transport model treats the bed and suspended load individually for each grain fraction, including effects associated with increased exposure of larger particles within a mixture. The suspended sediment transport model also makes use of modified reference concentration approach, wherein reference concentrations computed individually for each fraction are translated to a common level, conveniently enabling use of a single computational grid for the simulation of suspended sediments. Parametric study shows that these two effects combine to help alleviate an otherwise systematic tendency towards over- (under-) predicted transport rates for fine (coarse) sand fractions. The sediment transport model is validated against sheet-flow experimental oscillatory tunnel measurements beneath velocity-skewed wave signals, and demonstrates similar accuracy (transport rates generally within a factor of two) for both graded and uniform sands. The model is likewise validated against an extensive data set involving sheet-flow transport beneath acceleration-skewed wave signals (limited to uniform sands). It is then utilized to study potential effects of gradation on the net transport beneath such flows. The simulations suggest that gradation effects can both increase, as well as decrease, the total transport rate, depending largely on the behavior of the fine sand fraction. The model is implemented within the Matlab environment, and is freely available upon request to the corresponding author.

      PubDate: 2017-01-06T12:50:00Z
       
 
 
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