scholarly journals INDIVIDUAL WAVE EFFECTS ON COASTAL STRUCTURE DAMAGE DURING WINDSTORMS

2018 ◽  
pp. 14
Author(s):  
Gregory Westcott ◽  
Annette R. Grilli ◽  
Stephan Grilli ◽  
James T. Kirby ◽  
Fengyan Shi
Keyword(s):  
Structural Damage ◽  
Wave Interaction ◽  
Wave Theory ◽  
Conservation Equation ◽  
Wave Crest ◽  
Linear Wave ◽  
Structure Damage ◽  
Interaction Terms ◽  
Structural Loading ◽  
Set Up

In hazard assessment studies that evaluate the damage caused to coastal structures by windstorm-generated surge and waves, the standard approach has been to estimate structural loading by applying phase-averaged wave propagation models (e.g., SWAN, STWAVE) and storm surge models (e.g., ADCIRC), coupled or not with each other. Bare-earth “Digital Elevation Models” (DEMs) have typically been used as a basis for model grid development, with sometimes empirical adjustments being made to beach profiles or dune crest levels to account for storm-induced erosion. In recent work, the latter approach has been improved by including real time morphodynamic changes in simulations, using models such as XBeach (e.g., Schambach 2017; Schambach et al., 2017), which are still based on the wave action conservation equation, including semi-empirical parameterizations of wave breaking and many formulations based on linear wave theory (e.g., phase/group velocity, radiation stresses,…), as well as low-order wave-wave interaction terms. Finally, structural damage has typically been estimated based on empirical damage curves, developed based on field surveys, that use flow depth and controlling wave crest height as inputs (e.g., Grilli et al., 2017). Neglected in this modeling approach, however, are dynamic set-up and runup effects, as well as strongly nonlinear wave interactions that occur near and in the surf and swash zones.

scholarly journals BORE PROPAGATION SPEED AT THE TERMINATION OF WAVE BREAKING

2011 ◽  
Vol 1 (32) ◽  
pp. 7 ◽  
Author(s):  
Takashi Okamoto ◽  
Conceição Juana Fortes ◽  
David R. Basco
Keyword(s):  
Wave Breaking ◽  
Propagation Speed ◽  
Wave Theory ◽  
Theoretical Models ◽  
Breaking Wave ◽  
Linear Wave ◽  
Mass Transportation ◽  
Higher Harmonics ◽  
Wave Celerity ◽  
Set Up

Wave breaking is the most important event in nearshore hydrodynamics because of the energy exertion and mass transportation during the event drive all the nearshore phenomena, such as wave set-up/down, long shore current, and nearshore circulation. Wave celerity is a key parameter in wave breaking especially for the mass transportation, the energy dissipation during the wave breaking event, and the wave breaking index calculation, for example. There are many models to calculate the wave celerity during the breaking event (bore propagation speed) and it is well known that the bore propagation speed is faster than that is given by linear wave theory. But Okamoto et al. (2008) found the bore propagation speed at the termination location of wave breaking becomes much slower than the theoretical estimation when the termination of wave breaking occurs on inversely sloped bottom. In this paper, the bore propagation speed at the termination location of wave breaking is examined with the experimental data collected in a wave tank with simplified bar-trough beach settings. Comparisons with theoretical models are presented. Fourier analysis is performed to investigate the evolution of higher harmonics and synthesized time series, which is a simple summation of linear wave components, is constructed by using the obtained information to calculate the wave celerity during and after the wave breaking. Calculation result reveals that as the breaking wave approaches to the termination, the bore propagation speed decreases towards the value which can be explained by the existence of slowly and independently propagating higher harmonics.

Crest-Height Distribution in Nonlinear Random Wave

2009 ◽  
Author(s):  
Cuilin Li ◽  
Dingyong Yu ◽  
Yangyang Gao ◽  
Junxian Yang
Keyword(s):  
Nonlinear Wave ◽  
Wave Theory ◽  
Distribution Functions ◽  
Theoretical Distribution ◽  
Distribution Model ◽  
Stokes Wave ◽  
Wave Crest ◽  
Linear Wave ◽  
Height Distribution ◽  
Crest Height

Many empirical and theoretical distribution functions for wave crest heights have been proposed, but there is a lack of agreement. With the development of ocean exploitation, waves crest heights represent a key point in the design of coastal structures, both fixed and floating, for shoreline protection and flood prevention. Waves crest height is the dominant parameter in assessing the likelihood of wave-in-deck impact and its resulting severe damage. Unlike wave heights, wave crests generally appear to be affected by nonlinearities; therefore, linear wave theory could not be satisfied to practical application. It is great significant to estimate a new nonlinear wave crest height distribution model correctly. This paper derives an approximation distribution formula based on Stokes wave theory. The resulting theoretical forms for nonlinear wave crest are compared with observed data and discussed in detail. The results are shown to be in good agreement. Furthermore, the results indicate that the new theoretical distribution has more accurate than other methods presented in this paper (e.g. Rayleigh distribution and Weibull distribution) and appears to have a greater range of applicability.

scholarly journals Characteristics of Positive Surges in a Rectangular Channel

Water ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1473 ◽  
Author(s):  
Feidong Zheng ◽  
Yun Li ◽  
Guoxiang Xuan ◽  
Zhonghua Li ◽  
Long Zhu
Keyword(s):  
Rectangular Channel ◽  
Experimental Studies ◽  
Wave Theory ◽  
Progressive Increase ◽  
Wave Crest ◽  
Linear Wave ◽  
Sudden Increase ◽  
Initial Profile ◽  
Increasing Trend ◽  
Flow Motion

A positive surge is an unsteady open channel flow motion characterized by an increase of flow depth. In previous experimental studies, a positive surge was typically induced by either a sudden increase of discharge in a channel or by the rapid closure of a downstream sluice gate, thus leading to a steep initial profile. However, in many instances, the evolution of a positive surge is of a progressive manner (e.g., in the downstream navigation canal during the emptying operation of lock chambers). In the present work, the inception and development of a positive surge induced by a progressive increase of discharge was investigated in a rectangular channel with a smooth bed. Both undular and breaking surges were studied. The results demonstrate that the maximum wave height at the first wave crest of an undular surge is in very close agreement with the McCowan theory. Additionally, the wave amplitude essentially shows a linearly increasing trend with an increasing surge Froude number up to Fr0 = 1.26 to 1.28, whereas it tends to suggest a power law reduction for larger surge Froude numbers. Moreover, the dispersion of undular surges is consistent with the linear wave theory only for surge Froude numbers close to unity. Overall, the present study demonstrates the unique features of positive surges induced by a progressive increase of discharge.

Scattering of Waves by Two-Dimensional Circular Obstacles in Finite Water Depths

1979 ◽  
Vol 23 (01) ◽  
pp. 32-42 ◽  
Author(s):  
Robert A. Naftzger ◽  
Subrata K. Chakrabarti
Keyword(s):  
Wave Interaction ◽  
Wave Theory ◽  
Finite Depth ◽  
Wave Forces ◽  
Linear Wave ◽  
Two Dimensional ◽  
Linear Wave Theory ◽  
Dimensional Object ◽  
Limiting Case ◽  
Water Depths

The wave forces on a fixed two-dimensional object submerged in water of finite depth are obtained under the assumptions of linear wave theory. The far-field characteristics of the wave interaction with the object are also examined. The boundary-value problem for the wave potential is formulated in terms of Green's theorem, and the resulting integral equation is solved numerically. Results for a submerged and half-submerged circular cylinder and a bottom-seated half cylinder are presented. In the limiting case of infinite depth the numerical results compare quite well with known solutions.

Investigation of Shallow Water Kinematics and Local Loading Effects on Reliability of Minimum Structures

2001 ◽  
Vol 124 (1) ◽  
pp. 41-47
Author(s):  
Suhartodjo Tuty ◽  
Mark J. Cassidy ◽  
Beverley F. Ronalds
Keyword(s):  
Shallow Water ◽  
Stream Function ◽  
Function Theory ◽  
Strong Relationship ◽  
Wave Theory ◽  
Wave Crest ◽  
Linear Wave ◽  
North West ◽  
Wave Kinematics ◽  
The North

In shallow water, and specifically for minimum structures, the critical wave height exponent α has been shown to vary significantly with structural configuration. Because of the strong relationship to the wave kinematics, α is also sensitive to the wave theory chosen. The North West Shelf offshore Australia has numerous minimum structures located in relatively shallow water, which requires non-linear wave theory. In the near-breaking condition, estimation of the wave crest kinematics is difficult, with Stream Function theory being the most widely used. However, various other wave theories and nonlinear numerical techniques have been developed to predict wave kinematics for shallow water conditions. The following wave theories are compared: regular Stream Function theory, Cnoidal wave theory, Stokes’ theory, NewWave theory, and a second-order correction to NewWave theory. Kinematics, loads and α results are presented for a cylinder in three different water depths.

scholarly journals Three Dimensional Radiated Water Wave with a Submerged Cylinder in Presence of Circular Plate

2019 ◽  
Vol 9 (1) ◽  
pp. 6665-6670
Keyword(s):  
Separation Of Variables ◽  
Surface Condition ◽  
Three Dimensional ◽  
Wave Interaction ◽  
Wave Theory ◽  
Linear Wave ◽  
Energy Device ◽  
Linear Wave Theory ◽  
Bernoulli’S Equation ◽  
Submerged Cylinder

This work deals with the problem of radiated by wave interaction with a couple of submerged cylinders in water which can be considered as a wave energy device and the problem arising from the rotational motion of submerged upper cylinder which one contains in the device. In this work, we approach theoretically to solve the problem based on the method of separation of variables and we derive the radiated velocity potentials numerically based on linear wave theory and eigenfunctions are introduced for each region by using free surface condition. Then we calculate the hydrodynamic coefficients due to rotational of the upper cylinder by using Bernoulli’s equation of pressure by neglecting the atmospheric pressure and unknown constants are calculate by using matched conditions between the regions Finally, we present all numerical results graphically for different radii of the cylinders

Wave interactions in magnetohydrodynamics, and cosmic-ray-modified shocks

1999 ◽  
Vol 61 (2) ◽  
pp. 295-346 ◽  
Author(s):  
G. M. WEBB ◽  
A. ZAKHARIAN ◽  
M. BRIO ◽  
G. P. ZANK
Keyword(s):  
Cosmic Rays ◽  
Evolution Equations ◽  
Wave Interaction ◽  
Cosmic Ray ◽  
Alfvén Waves ◽  
Linear Wave ◽  
Wave Mixing ◽  
Background Flow ◽  
Wave Interactions ◽  
Interaction Terms

Multiple-scales perturbation methods are used to study wave interactions in magnetohydrodynamics (MHD), in one Cartesian space dimension, with application to cosmic-ray-modified shocks. In particular, the problem of the propagation and interaction of short wavelength MHD waves, in a large-scale background flow, modified by cosmic rays is studied. The wave interaction equations consist of seven coupled evolution equations for the backward and forward Alfvén waves, the backward and forward fast and slow magnetoacoustic waves and the entropy wave. In the linear wave regime, the waves are coupled by wave mixing due to gradients in the background flow, cosmic-ray squeezing instability effects, and damping due to the diffusing cosmic rays. In the most general case, the evolution equations also contain nonlinear wave interaction terms due to Burgers self wave steepening for the magnetoacoustic modes, resonant three wave interactions, and mean wave field interaction terms. The form of the wave interaction equations in the ideal MHD case is also discussed. Numerical simulations of the fully nonlinear cosmic ray MHD model equations are compared with spectral code solutions of the linear wave interaction equations for the case of perpendicular, cosmic-ray-modified shocks. The solutions are used to illustrate how the different wave modes can be generated by wave mixing, and the modification of the cosmic ray squeezing instability due to wave interactions. It is shown that the Alfvén waves are coupled to the magnetoacoustic and entropy waves due to linear wave mixing, only in background flows with non-zero field aligned electric current and/or vorticity (i.e. if B·∇×B≠0 and/or B·∇×u≠0, where B and u are the magnetic field induction and fluid velocity respectively).

Study on a Numerical Model of “Rainfall-Runoff” Process Combined with Snowmelt

2012 ◽  
Vol 518-523 ◽  
pp. 4273-4277
Author(s):  
Huang Jinbai ◽  
Wang Bin ◽  
Hinokidani Osamu ◽  
Kajikawa Yuki
Keyword(s):  
Numerical Method ◽  
Wave Theory ◽  
Large Error ◽  
Calculation Model ◽  
Surface Flow ◽  
Snow Melt ◽  
Rainfall Runoff ◽  
Surface Water Resources ◽  
Permissible Range ◽  
Set Up

In order to achieve the accurate calculation of “rainfall-runoff” process combined with snowmelt and to provide a useful numerical method for estimating surface water resources in a basin, a runoff numerical calculation model of “rainfall-runoff” process combined with snowmelt was developed for a distributive hydrological model. Numerical method on “Rainfall-runoff” process was set up by applying kinematic wave theory, and calculations on snowmelt were made using energy budget method. Validity of the model was verified through numerical simulation of the observed surface flow. Results of the error analysis indicated that a large error existed between the numerical results and the observed ones without considering snowmelt whereas the error was at the permissible range of criterion (< 3 %) by considering snowmelt. The results showed that the snowmelt calculation should be considered at snow melt area when performing the runoff calculation.

A Second Order Lagrangian Model for Irregular Ocean Waves

2005 ◽  
Vol 128 (3) ◽  
pp. 177-183 ◽  
Author(s):  
Sébastien Fouques ◽  
Harald E. Krogstad ◽  
Dag Myrhaug
Keyword(s):  
Specular Reflection ◽  
Fluid Velocity ◽  
Equations Of Motion ◽  
Wave Theory ◽  
Ocean Waves ◽  
Second Order ◽  
Lagrangian Model ◽  
Lagrangian Description ◽  
Linear Wave ◽  
Irregular Solution

Synthetic aperture radar (SAR) imaging of ocean waves involves both the geometry and the kinematics of the sea surface. However, the traditional linear wave theory fails to describe steep waves, which are likely to bring about specular reflection of the radar beam, and it may overestimate the surface fluid velocity that causes the so-called velocity bunching effect. Recently, the interest for a Lagrangian description of ocean gravity waves has increased. Such an approach considers the motion of individual labeled fluid particles and the free surface elevation is derived from the surface particles positions. The first order regular solution to the Lagrangian equations of motion for an inviscid and incompressible fluid is the so-called Gerstner wave. It shows realistic features such as sharper crests and broader troughs as the wave steepness increases. This paper proposes a second order irregular solution to these equations. The general features of the first and second order waves are described, and some statistical properties of various surface parameters such as the orbital velocity, slope, and mean curvature are studied.

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