scholarly journals HURRICANE STORM SURGE CONSIDERED AS A RESONANCE PHENOMENON

2011 ◽  
Vol 1 (7) ◽  
pp. 31 ◽  
Author(s):  
G. Abraham
Keyword(s):  
Gravity Waves ◽  
Constant Velocity ◽  
Resonance Phenomenon ◽  
Critical Conditions ◽  
Constant Depth ◽  
Local Disturbance ◽  
Maximum Value ◽  
Model Study ◽  
Wave Heights ◽  
Hurricane Storm Surge

A model study was performed to study the water gravity waves generated by a circular local disturbance of pressure, advancing with constant velocity over the surface of water of constant depth. The results indicate that under critical conditions a resonance type phenomenon occurs for which the associated wave heights have a maximum value. It is shown that the resonant conditions may be an important factor for the generation of the surge due to hurricanes, that approach the coast perpendicularly.

RESONANCE OF NONMODAL PERTURBATIONS IN THE BATCHELOR VORTEX

2010 ◽  
Vol 24 (13) ◽  
pp. 1449-1452
Author(s):  
ZHI-WEI GUO ◽  
DE-JUN SUN
Keyword(s):  
Resonant Mode ◽  
Resonance Phenomenon ◽  
Mode Switch ◽  
Energy Growth ◽  
Optimal Energy ◽  
Maximum Value ◽  
Resonant Character ◽  
Swirl Parameter

The resonance phenomenon for nonmodal perturbation of Batchelor vortex is studied. For azimuthal wavenumber n = - 1, two resonant peaks appear and the left one is always dominant. For n = 1, the resonant character becomes very complicated. There is a resonant mode switch from right peak to left peak as swirl parameter q increases from 2 to infinity. The resonant wavenumber k is the largest when q approaches to infinity for n = - 1 while it is the smallest for n = 1. The maximum value of the optimal energy growth for n = 1 is at q approaches to infinity, whereas it decreases monotonically as q increases for n = - 1. The resonance for n = - 1 is the more important one.

scholarly journals Focusing of long waves with finite crest over constant depth

2013 ◽  
Vol 469 (2153) ◽  
pp. 20130015 ◽  
Author(s):  
Utku Kânoğlu ◽  
Vasily V. Titov ◽  
Baran Aydın ◽  
Christopher Moore ◽  
Themistoklis S. Stefanakis ◽  
...  
Keyword(s):  
Source Region ◽  
Wave Theory ◽  
Long Waves ◽  
Constant Depth ◽  
Large Wave ◽  
Weakly Nonlinear ◽  
Scaling Relationships ◽  
2011 Japan Tsunami ◽  
Wave Heights ◽  
Run Up

Tsunamis are long waves that evolve substantially, through spatial and temporal spreading from their source region. Here, we introduce a new analytical solution to study the propagation of a finite strip source over constant depth using linear shallow-water wave theory. This solution is not only exact, but also general and allows the use of realistic initial waveforms such as N -waves. We show the existence of focusing points for N -wave-type initial displacements, i.e. points where unexpectedly large wave heights may be observed. We explain the effect of focusing from a strip source analytically, and explore it numerically. We observe focusing points using linear non-dispersive and linear dispersive theories, analytically; and nonlinear non-dispersive and weakly nonlinear weakly dispersive theories, numerically. We discuss geophysical implications of our solutions using the 17 July 1998 Papua New Guinea and the 17 July 2006 Java tsunamis as examples. Our results may also help to explain high run-up values observed during the 11 March 2011 Japan tsunami, which are otherwise not consistent with existing scaling relationships. We conclude that N -waves generated by tectonic displacements feature focusing points, which may significantly amplify run-up beyond what is often assumed from widely used scaling relationships.

scholarly journals On the Benjamin–Lighthill conjecture for water waves with vorticity

2017 ◽  
Vol 825 ◽  
pp. 961-1001 ◽  
Author(s):  
V. Kozlov ◽  
N. Kuznetsov ◽  
E. Lokharu
Keyword(s):  
Water Waves ◽  
Finite Depth ◽  
Two Dimensional ◽  
Constant Depth ◽  
Lipschitz Continuous ◽  
Vorticity Distribution ◽  
Inviscid Incompressible Fluid ◽  
Two Dimensional Flow ◽  
Wave Heights ◽  
Gravity Driven

We consider the nonlinear problem of steady gravity-driven waves on the free surface of a two-dimensional flow of an inviscid, incompressible fluid (say, water). The water motion is supposed to be rotational with a Lipschitz continuous vorticity distribution, whereas the flow of finite depth is assumed to be unidirectional. We verify the Benjamin–Lighthill conjecture for flows with values of Bernoulli’s constant close to the critical one. For this purpose it is shown that a set of near-critical waves consists only of Stokes and solitary waves provided their slopes are bounded by a constant. Moreover, the subset of waves with crests located on a fixed vertical is uniquely parametrised by the flow force, which varies between its values for the supercritical and subcritical shear flows of constant depth. There exists another parametrisation for this set; it involves wave heights varying between the constant depth of the subcritical shear flow and the height of a solitary wave.

scholarly journals Finite element simulation of marine generators

2020 ◽  
pp. 92-97
Author(s):  
А.В. Гринек ◽  
А.М. Фищенко ◽  
И.П. Бойчук ◽  
Д.Н. Перелыгин ◽  
Н.В. Савостеенко
Keyword(s):  
Wavelet Transform ◽  
Geometric Model ◽  
Harmonic Component ◽  
Low Frequency ◽  
Linkage Phase ◽  
Maximum Value ◽  
Model Study ◽  
Element Simulation ◽  
Frequency Components ◽  
Transform Coefficients

В статье рассмотрено численное моделирование синхронного генератора. Описана последовательность создания геометрической модели. Представлены результаты численного моделирования статической и динамической задачи. Получены временные осциллограммы потокосцепления, фазных токов и напряжений, сил и моментов. На их основании получены частотные характеристики заданного генератора на холостых режимах. С помощью вейвлет-преобразования проведен анализ переходного процесса. Исследование показало, что существует три частотные области: область нарастания скорости, достижение критической скорости и выход на установившийся режим. Анализ коэффициентов вейвлет-преобразования исследуемого сигнала дал информацию об энергии, содержащейся в соответствующих частотных составляющих ряда. Данная численная модель дает возможность идентифицировать спектры напряжений, токов, сил и моментов, соответствующих механическим и электромагнитным дефектам. Показана возможность диагностирования дефектов генератора, обусловленного эксцентриситетом ротора, с помощью модельного исследования на пусковых режимах. Наличие эксцентриситета ротора приводит к появлению гармонической составляющей в спектре силы большой амплитуды с максимальным значением на низкой частоте. The sequence of creating a geometric model is described. The results of numerical simulation of static and dynamic problems are presented. Time oscillograms of flux linkage, phase currents and voltages, forces and moments were obtained. The analysis of the transient process is carried out using the wavelet transform. The study showed that there are three frequency ranges: the area of increasing speed, reaching critical speed and reaching steady state. Analysis of the wavelet transform coefficients gave information about the energy, which is contained in the corresponding frequency components of the series. This numerical model makes it possible to identify the spectrum of voltages, currents, forces and moments corresponding to mechanical and electromagnetic defects. The possibility of diagnosing the eccentricity of the rotor using a model study in starting modes is shown. Eccentricity leads to the appearance of a harmonic component in the power spectrum with a large amplitude with a maximum value at a low frequency.

scholarly journals THE EFFECT OF ROUGHNESS ON THE MASS-TRANSPORT OF PROGRESSIVE GRAVITY WAVES

1966 ◽  
Vol 1 (10) ◽  
pp. 11 ◽  
Author(s):  
Arthur Brebner ◽  
J.A. Askew ◽  
S.W. Law
Keyword(s):  
Mass Transport ◽  
Gravity Waves ◽  
Orbital Motion ◽  
Wave Length ◽  
Wave Theory ◽  
Finite Amplitude ◽  
Maximum Value ◽  
Transport Velocity ◽  
Mass Transport Velocity ◽  
The Mean

On the basis of non-viscous small amplitude firstorder theory the maximum value of the horizontal orbital motion at the bed in water of constant depth his given by /U/n yy* »* " r •»** */i where k = /L, H is the wave height crest to trough, T is the period, and L the wave length (L = Sry2jr Arf 2*%/L ). On the basis of finite amplitude wave theory where the particle orbits are not closed ana by the insertion of the viscous laminar boundary layer (the conducti6n solution) the mean drift velocity or mass transport velocity on a perfectly smooth bed is given by Longuet- Higgins (1952) as 7, K H* kcr where

scholarly journals Advection and dispersion of bed load tracers

2018 ◽  
Vol 6 (2) ◽  
pp. 389-399 ◽  
Author(s):  
Eric Lajeunesse ◽  
Olivier Devauchelle ◽  
François James
Keyword(s):  
Steady State ◽  
Steady Flow ◽  
Constant Velocity ◽  
Transport Rate ◽  
Bed Load ◽  
Deposition Model ◽  
Advection Diffusion ◽  
Maximum Value ◽  
Load Transport ◽  
Bed Load Transport

Abstract. We use the erosion–deposition model introduced by Charru et al. (2004) to numerically simulate the evolution of a plume of bed load tracers entrained by a steady flow. In this model, the propagation of the plume results from the stochastic exchange of particles between the bed and the bed load layer. We find a transition between two asymptotic regimes. The tracers, initially at rest, are gradually set into motion by the flow. During this entrainment regime, the plume is strongly skewed in the direction of propagation and continuously accelerates while spreading nonlinearly. With time, the skewness of the plume eventually reaches a maximum value before decreasing. This marks the transition to an advection–diffusion regime in which the plume becomes increasingly symmetrical, spreads linearly, and advances at constant velocity. We analytically derive the expressions of the position, the variance, and the skewness of the plume and investigate their asymptotic regimes. Our model assumes steady state. In the field, however, bed load transport is intermittent. We show that the asymptotic regimes become insensitive to this intermittency when expressed in terms of the distance traveled by the plume. If this finding applies to the field, it might provide an estimate for the average bed load transport rate.

Parameterizing gravity waves in the DYNAMICO-Saturn Global Climate Model to understand Saturn's equatorial oscillation

2020 ◽  
Author(s):  
Deborah Bardet ◽  
Aymeric Spiga ◽  
Sandrine Guerlet ◽  
Ehouarn Millour ◽  
François Lott
Keyword(s):  
Gravity Waves ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Life Cycles ◽  
Small Scale ◽  
Mean Flow ◽  
Time Step ◽  
Maximum Value ◽  
The Mean

<p>To address questions about the driving mechanisms of Saturn's equatorial oscillation, our team at the Laboratoire de Météorologie Dynamique built the DYNAMICO-Saturn Global Climate Model to study tropospheric dynamics, tropospheric waves activity (Spiga et al. 2020) and equatorial stratospheric dynamics (Bardet et al. 2020) of Saturn. Previous studies (Guerlet et al. 2014, Spiga et al. 2020, Cabanes et al. 2020) have shown that our model produces consistent thermal structure and seasonal variability compared to Cassini CIRS measurements, mid-latitude eddy-driven tropospheric eastward and westward jets commensurate to those observed and following the zonostrophic regime, and planetary-scale waves such as Rossby-gravity (Yanai), Rossby and Kelvin waves in the tropical channel. Extending the model top toward the upper stratosphere allowed our model to produce an almost semi-annual equatorial oscillation with opposite eastward and westward phases. Associated temperature anomalies have a similar behavior than the Cassini/CIRS observations, but the amplitude of the temperature oscillation is twice smaller than the observed one. The absence of sub-grid-scale waves in the model produces an imbalance in eastward- and westward-wave forcing on the mean flow and could be an explanation to the irregularity in both the oscillating period and the downward rate propagation of the resolved Saturn equatorial oscillation.</p> <p>To explore the impact of those small-scale waves on the spontaneous equatorial oscillation emerging in the DYNAMICO-Saturn GCM (Bardet et al. 2020), we add a sub-grid-scale non-orographic gravity waves drag parameterization in our model.<br />This parameterization is directly adapted from the stochastic terrestrial model of Lott et al. (2012). This formalism represents a broadband gravity wave spectrum, using the superposition of a large statistical set of monochromatic waves. As the time scale of the life cycles of gravity waves is much longer than the time step of our GCM, our parametrization can launch a few waves whose characteristics are randomly chosen at each time step. This stochastic gravity waves drag parameterization is applied in DYNAMICO-Saturn on all points of the horizontal grid.</p> <p>A key parameter used in the non-orographic gravity waves drag parameterization is the maximum value of the Eliassen-Palm flux. The Eliassen Palm flux represents the momentum carried by waves that could be transferred to the mean flow. This value has never been measured in Saturn's atmosphere and it represents an important degree of freedom in the parameterization of gravity waves.</p> <p>We performed several test simulations, lasting two Saturn years whose initial state is derived from Bardet et al (2020), with an horizontal resolution of 1/2° in longitude/latitude and a vertical resolution ranging between 3 bar to 1 μbar. For these test simulations, the maximum value of the Eliassen-Palm fulx is set to 10<sup>-6</sup>, 10<sup>-5</sup>, 10<sup>-4</sup> and 10<sup>-3</sup> kg m<sup>-1</sup> s<sup>-2</sup>. </p> <p>Preliminary results show that the appropriate value of our main parameter is between 10<sup>-5</sup> and 10<sup>-4</sup> kg m<sup>-1</sup> s<sup>-2</sup>. Eliassen-Palm flux value of 10<sup>-3</sup> kg m<sup>-1</sup> s<sup>-2</sup> demonstrates a too large impact: the equatorial oscillation is entirely vanished is this configuration. The simulation using the value of 10<sup>-6</sup> kg m<sup>-1</sup> s<sup>-2</sup> is equivalent to the control simulation without the gravity waves drag parameterization.  </p> <p>The next step is to test other parameters, as phase velocity of the gravity waves, horizontal wavenumber, to understand how gravity waves impact the equatorial oscillation.</p>

scholarly journals Nonlinear dispersion for ocean surface waves

2018 ◽  
Vol 859 ◽  
pp. 49-58 ◽  
Author(s):  
Raphael Stuhlmeier ◽  
Michael Stiassnie
Keyword(s):  
Gravity Waves ◽  
Energy Spectra ◽  
Two Dimensional ◽  
Nonlinear Dispersion ◽  
Constant Depth ◽  
Wave Fields ◽  
Numerical Examples ◽  
Ocean Surface Waves ◽  
Nonlinear Dispersion Relation ◽  
Amplitude Spectra

Two expressions for the nonlinear dispersion relation for gravity waves on water of constant depth are derived, one for wave fields with discrete amplitude spectra, the other for wave fields with continuous wavenumber energy spectra. Numerical examples for wave quartets and for two-dimensional Pierson–Moskowitz spectra are given, and an important possible application is discussed.

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