scholarly journals INSHORE-NEARSHORE MORPHODYNAMICS - A PREDICTIVE MODEL

1980 ◽  
Vol 1 (17) ◽  
pp. 59 ◽  
Author(s):  
John Chappell
Keyword(s):  
Wave Train ◽  
Two Dimensional ◽  
Radiation Stress ◽  
Wave Refraction ◽  
Gradient Effect ◽  
Sediment Drift ◽  
Sea Bed ◽  
Equilibrium Topography ◽  
Standard Wave ◽  
Input Wave

The two-dimensional topography, developed on a sandy sea bed between surf base and the breaker zone, is computed using (i) sediment gain or loss per unit bed area = zero, (ii) simple models of sediment drift in terms of, firstly, simplified saltation under Stokesian waves, and secondly, frictional wave work on the sea bed, (iii) the drift tendency in direction of wave propogation being offset of the local sea bed gradient. An input contour line at surf base is assumed, across which the input wave train is propogated. Using standard wave refraction combined with (i) to (iii), above, an equilibrium topography is generated by iteration. Inshore of the breaker line, longshore currents generated by radiation stress are combined with the gradient effect to balance sediment drift, producing bar - trough topography.

scholarly journals LABORATORY STUDY ON TWO-DIMENSIONAL BEACH TRANSFORMATION DUE TO IRREGULAR WAVES

1986 ◽  
Vol 1 (20) ◽  
pp. 102 ◽  
Author(s):  
Nubuo Mimura ◽  
Yukinori Otsuka ◽  
Akira Watanabe
Keyword(s):  
Wave Train ◽  
Irregular Waves ◽  
Two Dimensional ◽  
Beach Profile ◽  
Irregular Wave ◽  
Sand Ripple ◽  
Ripple Formation ◽  
Sand Movement ◽  
Incident Waves ◽  
Profile Change

In the present study, effects of irregular waves on two-dimensional beach transformation and related phenomena were investigated through a series of laboratory experiments. Attempts were made to determine a representative wave of irregular wave trains which controlled individual phenomenon related to the two-dimensional beach profile change. It was found that the representative wave is different for each phenomenon. For the macroscopic beach profile change, it is the mean wave which represents whole incident waves. On the other hand, some of microscopic phenomena, such as initiation of sand movement and sand ripple formation, are controlled by larger waves in the wave train selectively, of which representative wave is the significant wave.

Tsunami generation

1973 ◽  
Vol 59 (4) ◽  
pp. 817-828 ◽  
Author(s):  
R. D. Braddock ◽  
P. Van Den Driessche ◽  
G. W. Peady
Keyword(s):  
Stationary Phase ◽  
Wave Front ◽  
Integral Transform ◽  
Wave Train ◽  
Asymptotic Approximations ◽  
Two Dimensional ◽  
Tsunami Generation ◽  
One Dimensional ◽  
Series Representations ◽  
Surface Disturbances

The problems of tsunami generation are treated by standard integral-transform and modified stationary-phase methods to yield asymptotic approximations to the surface disturbances. The effects of asymmetry are considered in a one-dimensional ocean. Series representations are used to produce sets of normal-mode oscillations in a two-dimensional ocean, and the magnitudes of the wave front and wave train are discussed in relation to the asymmetry of the generating region.

Weak quadratic interactions of two-dimensional waves

1971 ◽  
Vol 50 (1) ◽  
pp. 107-132 ◽  
Author(s):  
Young Yuel Kim ◽  
Thomas J. Hanratty
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Wave Train ◽  
Water Layer ◽  
Rate Of Change ◽  
Two Dimensional ◽  
Low Frequencies ◽  
Resonant Interactions ◽  
Water Layers ◽  
Phase Angles

This paper reports on weak quadratic interactions which can occur with two-dimensional waves on shallow water layers and in the capillary-gravity range on deep water layers. It supplies experimental support of theoretical predictions for resonant interactions, but, perhaps of more significance, it explores in detail interactions which occur under conditions near resonance.Waves of approximately sinusoidal form are introduced on the surface of water in a long rectangular tank. For deep water a rapid distortion in the sinusoidal wave and sometimes additional crests are observed because of energy exchange among the first, second and third harmonics at frequencies where both surface tension and gravity are important (7·5–13 c/s). An even greater exchange of energy can be observed on shallow water layers at low frequencies. For example, a wave train with seven secondary crests can be observed when the wave maker is operated at 3·04 c/s in a water layer of 0·65 cm.Measured amplitudes and phase angles of the Fourier components of the wave train are described by a system of equations using only quadratic interactions among participating harmonics. The exchange of energy among Fourier components under certain conditions is explained in terms of the rate of change of relative phase angles of the different harmonics.

Cross-Flow Vibrations of a Pipe Close to a Rigid Boundary

1984 ◽  
Vol 106 (4) ◽  
pp. 451-457 ◽  
Author(s):  
V. Jacobsen ◽  
M. B. Bryndum ◽  
R. Nielsen ◽  
S. Fines
Keyword(s):  
Wave Train ◽  
Cross Flow ◽  
Flow Conditions ◽  
Rigid Boundary ◽  
Irregular Wave ◽  
Steady Current ◽  
Sea Bed ◽  
Velocity Flow ◽  
Pipe Segment ◽  
Hydroelastic Vibrations

The paper describes the results of a model test series with the purpose of determining the hydroelastic vibrations of a nearbed pipeline span exposed to flow conditions created by steady current, waves and waves superimposed on steady current. The study has been conducted using a model composed of a spring-mounted rigid pipe segment and a flat plate simulating the sea bed. The hydroelastic cross-flow vibrations of the pipe segment are presented as function of the flow velocity, flow condition (waves and/or steady current) and the relative distance of the pipe to the seabed. A simple approach to analyze the vibrations caused by an irregular wave train is presented.

Long wave propagation and run-up in converging bays

2016 ◽  
Vol 798 ◽  
pp. 457-484 ◽  
Author(s):  
Takenori Shimozono
Keyword(s):  
Cross Sections ◽  
Wave Equations ◽  
Order Effect ◽  
Higher Order ◽  
Two Dimensional ◽  
Wave Refraction ◽  
Flow Acceleration ◽  
Run Up ◽  
A Minor ◽  
Higher Order Corrections

Analytical solutions are derived to describe two-dimensional wave evolution in converging bays. Three bay types of different cross-sections are studied: U-shaped, V-shaped and cusped bays. For these bays, the two-dimensional linear shallow water equations can be reduced to one-dimensional linear dispersive wave equations if the transverse flow acceleration inside them is assumed to be small. The derived solutions are characterized as the leading-order plane-wave solutions with higher-order corrections for two-dimensionality due to wave refraction. Wave amplitude longitudinally increases with different rates for the three bay types, whereas it exhibits weak parabolic variations in the transverse direction. Wave refraction significantly affects relatively short waves, contributing to wave energy transfer to the inner bay in a different manner depending on the bay type. The perturbation analysis of very high-order wave celerity suggests that the solutions are valid only when the ratio of the bay width to the wavelength is smaller than a certain limit that differs with bay type. Beyond the limit, the higher-order effect is no longer a minor correction, implying that wave behaviours become highly two-dimensional and possibly cause total reflection. The higher-order effect on the run-up height at the bay head is found to be small within the applicable range of the solution, and thus, the run-up formula neglecting the transverse flows has a wide validity. We also discuss the limitation of run-up height by wave breaking on the basis of a breaking criterion from previous studies.

scholarly journals Wave Trajectory Study on the Coast of Lhoknga, Aceh Besar, Indonesia: A Numerical Model Approach

2018 ◽  
Vol 20 (1) ◽  
pp. 30 ◽  
Author(s):  
Ichsan Setiawan ◽  
Mohammad Irham
Keyword(s):  
Numerical Model ◽  
Wave Height ◽  
Coastal Waters ◽  
Wave Breaking ◽  
Numerical Study ◽  
High Tide ◽  
Two Dimensional ◽  
Maximum Wave Height ◽  
Wave Refraction ◽  
Model Approach

A numerical model of wave trajectory using shoaling and refraction formula was proposed in the coastal waters of Lhoknga, Aceh Besar, Indonesia. The developed model used a two dimensional (2D) numerical methods for wave trajectory with the input of wave height and period; 0.62 m and 8 second for high tide and 0.47 m and 6 second for low tide. This model was tested on site during low tide and high tide conditions for verification. The purpose of this numerical study is to trace the distribution of wave trajectory because of shoaling, wave breaking, and wave refraction. The model determines the wave height and crest pattern of the ray wave trajectory. The simulation result shows the pattern of the wave propagation at Lhoknga beach moves from the northwest to the east and south of the coast. The model also informs that the maximum wave height during high tide condition is 1.72 m and 1.31 m during low tide condition. The result indicates that the coast of Lhoknga has moderate wave conditions caused by a gentle beach bathymetry slope.

Numerical Simulation of Motions of Two-Dimensional Floating Bodies

1993 ◽  
Vol 37 (04) ◽  
pp. 307-330
Author(s):  
D. Sen
Keyword(s):  
Wave Train ◽  
Boundary Integral ◽  
Nonlinear Phenomena ◽  
Computational Domain ◽  
Two Dimensional ◽  
Floating Bodies ◽  
Basic Algorithm ◽  
Numerical Predictions ◽  
Nonlinear Free Surface ◽  
Surface Constraints

A potential-flow numerical model is described for time-simulation of motions of two-dimensional floating bodies subjected to an oncoming wave train. The model is fully nonlinear in that no assumptions of smallness either in wave steepness or in body motions are made. The basic algorithm is based on a boundary integral formulation and time-stepping of the nonlinear free-surface constraints in an Eulerian frame of reference. Simple techniques are devised to overcome numerical instability problems that are encountered in the proposed method. The simulation time can be extended over several periods of steady-state oscillations depending on the size of the computational domain. Several illustrative results simulating large heave and roll motions as well as drifting of a rectangular body are presented and discussed. The numerical predictions are also evaluated against model tests which include several nonnegligible nonlinear phenomena, and the agreement is encouraging.

Transverse instabilities of deep-water solitary waves

2006 ◽  
Vol 462 (2071) ◽  
pp. 2039-2061 ◽  
Author(s):  
Bernard Deconinck ◽  
Dmitry E Pelinovsky ◽  
John D Carter
Keyword(s):  
Growth Rate ◽  
Deep Water ◽  
Wave Train ◽  
Two Dimensional ◽  
Nls Equation ◽  
One Dimensional ◽  
Hill’S Method ◽  
Real Growth ◽  
Dimensional Soliton ◽  
Complex Growth Rate

The dynamics of a one-dimensional slowly modulated, nearly monochromatic localized wave train in deep water is described by a one-dimensional soliton solution of a two-dimensional nonlinear Schrödinger (NLS) equation. In this paper, the instability of such a wave train with respect to transverse perturbations is examined numerically in the context of the NLS equation, using Hill's method. A variety of instabilities are obtained and discussed. Among these, we show that the solitary wave is susceptible to an oscillatory instability (complex growth rate) due to perturbations with arbitrarily short wavelength. Further, there is a cut-off on the instability with real growth rates. We show analytically that the nature of this cut-off is different from what is claimed in previous works.

scholarly journals TWO-DIMENSIONAL EMPIRICAL EIGENFUNCTION MODEL FOR THE ANALYSIS AND PREDICTION OF BEACH PROFILE CHANGES

1986 ◽  
Vol 1 (20) ◽  
pp. 87 ◽  
Author(s):  
T.W. Hsu ◽  
S.R. Liaw ◽  
S.K. Wang ◽  
S.H. Ou
Keyword(s):  
Breaking Waves ◽  
Relative Importance ◽  
Two Dimensional ◽  
Coastal Structures ◽  
Beach Profile ◽  
Radiation Stress ◽  
Profile Data ◽  
Profile Changes ◽  
D Model ◽  
Profile Change

A two-dimensional empirical eigenfunction model is proposed for the analysis and the prediction of beach profile change due to longshore and cross-shore sediment transports. Beach profile data from Redhill coast, Taiwan, measured every two months at 150 meters interval along the detached breakwaters are analyzed and the relative importance from two directions is investigated. Furthermore, by employing the method of Markov process and linear regression, a prediction model is formulated which takes into account the effect of breaking waves, bottom sediment and radiation stress of waves. This 2-D model is shown to be effective in the analysis and the prediction of beach changes near the coastal structures.

Swimming of a waving plate

1961 ◽  
Vol 10 (3) ◽  
pp. 321-344 ◽  
Author(s):  
T. Yao-Tsu Wu
Keyword(s):  
General Theory ◽  
Phase Velocity ◽  
Wave Train ◽  
Leading Edge ◽  
Basic Mechanism ◽  
Simplified Model ◽  
Two Dimensional ◽  
Propulsive Efficiency ◽  
Fish Propulsion ◽  
Solid Plate

The purpose of this paper is to study the basic principle of fish propulsion. As a simplified model, the two-dimensional potential flow over a waving plate of finite chord is treated. The solid plate, assumed to be flexible and thin, is capable of performing the motion which consists of a progressing wave of given wavelength and phase velocity along the chord, the envelope of the wave train being an arbitrary function of the distance from the leading edge. The problem is solved by applying the general theory for oscillating deformable airfoils. The thrust, power required, and the energy imparted to the wake are calculated, and the propulsive efficiency is also evaluated. As a numerical example, the waving motion with linearly varying amplitude is carried out in detail. Finally, the basic mechanism of swimming is elucidated by applying the principle of action and reaction.

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