Laboratory Experiment and Three-Dimensional Large Eddy Simulation of Wave Overtopping on Gentle Slope Seawalls

Okayasu, Akio; Suzuki, Takayuki; Matsubayashi, Yuriko

doi:10.1142/s0578563405001215

Cited by 11 publications

(4 citation statements)

References 16 publications

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“…where  is the kinematic viscosity coefficient,   is the kinematic eddy viscosity of SGS, ∆ is the filter length scale, and   is the deformation tensor at the grid size. As for the   value, Schumann (1987) proposed a value ranging from 0.07 to 0.21, but 0.1 was used in this study because it was applied in a similar study (Christensen and Deigaard, 2001;Okayasu et al, 2005). (1) From the hydraulic model experiment, the reflection coefficient, transmission coefficient, and energy dissipation coefficient according to the cross-section changes in vegetation were calculated.…”

Section: Results Of the Numerical Model Experimentsmentioning

confidence: 99%

Analysis of Hydraulic Characteristics According to the Cross-Section Changes in Submerged Rigid Vegetation

Lee¹,

Jeong²,

Kim³

et al. 2022

J. Ocean Eng. Technol.

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<i>Recently, not only Korea but also the world has been suffering from problems related to coastal erosion. The hard defense method has been primarily used as a countermeasure against erosion. However, this method is expensive and has environmental implications. Hence, interest in other alternative methods, such as the eco-friendly vegetation method, is increasing. In this study, we aim to analyze the hydraulic characteristic of submerged rigid vegetation according to the cross-sectional change through a hydraulic experiment and numerical simulation. From the hydraulic experiment, the reflection coefficient, transmission coefficient, and energy dissipation coefficient were analyzed according to the density, width, and multi-row arrangement of the vegetation zone. From numerical simulations, the flow field, vorticity distribution, turbulence distribution, and wave distribution around the vegetation zone were analyzed according to the crest depth, width, density, and multi-row arrangement distance of the vegetation zone. The hydraulic experiment results suggest that the transmission coefficient decreased as the density and width of the vegetation zone increased, and the multi-row arrangement condition did not affect the hydraulic characteristics significantly. Moreover, the numerical simulations showed that as the crest depth decreased, the width and density of vegetation increased along with vorticity and turbulence intensity, resulting in increased wave height attenuation performance. Additionally, there was no significant difference in vorticity, turbulence intensity, and wave height attenuation performance based on the multi-row arrangement distance. Overall, in the case of submerged rigid vegetation, the wave energy attenuation performance increased as the density and width of the vegetation zone increased and crest depth decreased. However, the multi-row arrangement condition did not affect the wave energy attenuation performance significantly.</i>

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Section: Results Of the Numerical Model Experimentsmentioning

confidence: 99%

Analysis of Hydraulic Characteristics According to the Cross-Section Changes in Submerged Rigid Vegetation

Lee¹,

Jeong²,

Kim³

et al. 2022

J. Ocean Eng. Technol.

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“…A three-dimensional (3D) LES model was proposed by Li et al [170] to study overtopping of sloped and vertical structures and produced promising results when ran on high resolution grids; however, grid dependency was observed. Similarly, Okayasu et al [139] extended a 3D LES model to investigate wave overtopping on gentle slopes and stepped sea walls, and results suggested a sensitivity to water depth at the structure toe. Lagrangian methods for solving the Navier-Stokes have gained some attention within the scientific community and are attractive because the method is meshless and requires no special surface tracking [157].…”

Section: Navier-stokes Equationsmentioning

confidence: 98%

“…Numerical models represent the current state-of-the-art for simulating overtopping flows and theoretically, if the physics are well represented, could predict overtopping in an infinite number of dune, dike or wall configurations. However, field scale implementations have been challenged by computational effort, grid sensitivities, and boundary condition effects which have restricted most applications to numerical wave flumes (e.g., [136]) or analytical solutions and laboratory validation data (e.g., [121,[137][138][139]).…”

Section: Wave Overtoppingmentioning

confidence: 99%

Coastal Flood Modeling Challenges in Defended Urban Backshores

et al. 2018

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Coastal flooding is a significant and increasing hazard. There are multiple drivers including rising coastal water levels, more intense hydrologic inputs, shoaling groundwater and urbanization. Accurate coastal flood event prediction poses numerous challenges: representing boundary conditions, depicting terrain and hydraulic infrastructure, integrating spatially and temporally variable overtopping flows, routing overland flows and incorporating hydrologic signals. Tremendous advances in geospatial data quality, numerical modeling and overtopping estimation have significantly improved flood prediction; however, risk assessments do not typically consider the co-occurrence of multiple flooding pathways. Compound flooding refers to the combined effects of marine and hydrologic processes. Alternatively, multiple flooding source–receptor pathways (e.g., groundwater–surface water, overtopping–overflow, surface–sewer flow) may simultaneously amplify coastal hazard and vulnerability. Currently, there is no integrated framework considering compound and multi-pathway flooding processes in a unified approach. State-of-the-art urban coastal flood modeling methods and research directions critical to developing an integrated framework for explicitly resolving multiple flooding pathways are presented.

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“…To conduct a calculation in a scale of the actual surf zone, LES, which describes the motion of vortices smaller than the grid size by Sub-Grid-Scale (SGS) turbulence model is one of candidates ( e.g. , Christensen and Deigaard, 2001; 27 ) Okayasu et al , 2005 28 ) ).…”

Section: Calculation Of Sediment Transport With Numerical Wave Flumementioning

confidence: 99%

Computational wave dynamics for innovative design of coastal structures

Gotoh

Okayasu

2017

Proceedings of the Japan Academy. Ser. B: Physical and Biologic

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For innovative designs of coastal structures, Numerical Wave Flumes (NWFs), which are solvers of Navier-Stokes equation for free-surface flows, are key tools. In this article, various methods and techniques for NWFs are overviewed. In the former half, key techniques of NWFs, namely the interface capturing (MAC, VOF, C-CUP) and significance of NWFs in comparison with the conventional wave models are described. In the latter part of this article, recent improvements of the particle method are shown as one of cores of NWFs. Methods for attenuating unphysical pressure fluctuation and improving accuracy, such as CMPS method for momentum conservation, Higher-order Source of Poisson Pressure Equation (PPE), Higher-order Laplacian, Error-Compensating Source in PPE, and Gradient Correction for ensuring Taylor-series consistency, are reviewed briefly. Finally, the latest new frontier of the accurate particle method, including Dynamic Stabilization for providing minimum-required artificial repulsive force to improve stability of computation, and Space Potential Particle for describing the exact free-surface boundary condition, is described.

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Laboratory Experiment and Three-Dimensional Large Eddy Simulation of Wave Overtopping on Gentle Slope Seawalls

Cited by 11 publications

References 16 publications

Analysis of Hydraulic Characteristics According to the Cross-Section Changes in Submerged Rigid Vegetation

Analysis of Hydraulic Characteristics According to the Cross-Section Changes in Submerged Rigid Vegetation

Coastal Flood Modeling Challenges in Defended Urban Backshores

Computational wave dynamics for innovative design of coastal structures

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