scholarly journals TIDAL INLET CURRENT--OCEAN WAVE INTERACTION

1972 ◽  
Vol 1 (13) ◽  
pp. 33 ◽  
Author(s):  
Lyndell Z. Hales ◽  
John B. Herbich
Keyword(s):  
Gravity Waves ◽  
Functional Relationship ◽  
Three Dimensional ◽  
Wave Interaction ◽  
Tidal Inlet ◽  
Surface Gravity Waves ◽  
Wave Characteristics ◽  
Wave Basin ◽  
Ocean Region ◽  
A Current

An experimental study was conducted in a three-dimensional wave basin to investigate the manner in which surface gravity waves propagating toward a tidal inlet are altered. Dimensional analysis of the pertinent variables indicates that a functional relationship exists between as many as five dimensionless terms, and the functional relationship is displayed in graphical non-dimensional form to apply to all scales. Results indicate the ebb current increases the steepness in the ocean region to such an extent that the wave begins to lose energy by the crest spilling down the front of the wave, and the wave characteristics in the inlet proper may never reach the breaking limit unless factors other than a current alone are involved.

scholarly journals Statistical properties of mechanically generated surface gravity waves: a laboratory experiment in a three-dimensional wave basin

2009 ◽  
Vol 627 ◽  
pp. 235-257 ◽  
Author(s):  
M. ONORATO ◽  
L. CAVALERI ◽  
S. FOUQUES ◽  
O. GRAMSTAD ◽  
P. A. E. M. JANSSEN ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Three Dimensional ◽  
Order Theory ◽  
Second Order ◽  
Statistical Properties ◽  
Surface Elevation ◽  
Surface Gravity ◽  
Surface Gravity Waves ◽  
Wave Basin ◽  
Dimensional Wave

A wave basin experiment has been performed in the MARINTEK laboratories, in one of the largest existing three-dimensional wave tanks in the world. The aim of the experiment is to investigate the effects of directional energy distribution on the statistical properties of surface gravity waves. Different degrees of directionality have been considered, starting from long-crested waves up to directional distributions with a spread of ±30° at the spectral peak. Particular attention is given to the tails of the distribution function of the surface elevation, wave heights and wave crests. Comparison with a simplified model based on second-order theory is reported. The results show that for long-crested, steep and narrow-banded waves, the second-order theory underestimates the probability of occurrence of large waves. As directional effects are included, the departure from second-order theory becomes less accentuated and the surface elevation is characterized by weak deviations from Gaussian statistics.

scholarly journals TOMOGRAPHY OF THE SOLAR INTERIOR

2006 ◽  
Vol 21 (22) ◽  
pp. 1701-1715 ◽  
Author(s):  
L. GIZON
Keyword(s):  
Gravity Waves ◽  
Acoustic Waves ◽  
Solar Surface ◽  
Three Dimensional ◽  
Magnetic Activity ◽  
Solar Interior ◽  
Turbulent Convection ◽  
Convective Structures ◽  
Surface Gravity Waves ◽  
Rich Spectrum

Solar oscillations consist of a rich spectrum of internal acoustic waves and surface gravity waves, stochastically excited by turbulent convection. They have been monitored almost continuously over the last ten years with high-precision Doppler images of the solar surface. The purpose of helioseismology is to retrieve information about the structure and the dynamics of the solar interior from the frequencies, phases and amplitudes of solar waves. Methods of analysis are being developed to make three-dimensional images of subsurface motions and temperature inhomogeneities in order to study convective structures and regions of magnetic activity, like sunspots.

scholarly journals Scattering of surface gravity waves by bottom topography with a current

2007 ◽  
Vol 576 ◽  
pp. 235-264 ◽  
Author(s):  
FABRICE ARDHUIN ◽  
RUDY MAGNE
Keyword(s):  
Gravity Waves ◽  
Bottom Topography ◽  
Wave Spectrum ◽  
Action Spectrum ◽  
Wave Action ◽  
Surface Gravity ◽  
Small Scale ◽  
Surface Gravity Waves ◽  
Reflected Wave ◽  
A Current

A theory is presented that describes the scattering of random surface gravity waves by small-amplitude topography, with horizontal scales of the order of the wavelength, in the presence of an irrotational and almost uniform current. A perturbation expansion of the wave action to order η2 yields an evolution equation for the wave action spectrum, where η = max(h)/H is the small-scale bottom amplitude normalized by the mean water depth. Spectral wave evolution is proportional to the bottom elevation variance at the resonant wavenumbers, representing a Bragg scattering approximation. With a current, scattering results from a direct effect of the bottom topography, and an indirect effect of the bottom through the modulations of the surface current and mean surface elevation. For Froude numbers of the order of 0.6 or less, the bottom topography effects dominate. For all Froude numbers, the reflection coefficients for the wave amplitudes that are inferred from the wave action source term are asymptotically identical, as η goes to zero, to previous theoretical results for monochromatic waves propagating in one dimension over sinusoidal bars. In particular, the frequency of the most reflected wave components is shifted by the current, and wave action conservation results in amplified reflected wave energies for following currents. Application of the theory to waves over current-generated sandwaves suggests that forward scattering can be significant, resulting in a broadening of the directional wave spectrum, while back-scattering should be generally weaker.

scholarly journals On the strength of the weakly nonlinear theory for surface gravity waves

2016 ◽  
Vol 810 ◽  
pp. 1-4 ◽  
Author(s):  
Michael Stiassnie
Keyword(s):  
Gravity Waves ◽  
Nonlinear Theory ◽  
Mathematical Formulation ◽  
Wave Theory ◽  
Quantitative Agreement ◽  
Surface Gravity ◽  
Weakly Nonlinear ◽  
Surface Gravity Waves ◽  
Weakly Nonlinear Theory ◽  
Wave Basin

Recently, Bonnefoy et al. (J. Fluid Mech., vol. 805, 2016, R3) studied the resonant interaction of oblique surface gravity waves in a large $50~\text{m}\times 30~\text{m}\times 5~\text{m}$ wave basin. Their experimental results are in excellent quantitative agreement with predictions of the weakly nonlinear wave theory, and provide additional evidence to the strength of this widely used mathematical formulation. In this article, the reader is introduced to the many facets of the weakly nonlinear theory for surface gravity waves, and to its current and possible future applications, deterministic as well as stochastic.

scholarly journals Cloaking of a vertical cylinder in waves using variable bathymetry

2014 ◽  
Vol 750 ◽  
pp. 124-143 ◽  
Author(s):  
R. Porter ◽  
J. N. Newman
Keyword(s):  
Gravity Waves ◽  
Wave Equations ◽  
Three Dimensional ◽  
Vertical Cylinder ◽  
Dimensional Problem ◽  
Practical Application ◽  
Surface Gravity Waves ◽  
Dimensional Boundary ◽  
Drift Force ◽  
Numerical Optimisation

AbstractThe paper describes a process which allows a vertical circular cylinder subject to plane monochromatic surface gravity waves to appear invisible to the far-field observer. This is achieved by surrounding the cylinder with an annular region of variable bathymetry. Two approaches are taken to investigate this effect. First a mild-slope approximation is applied to the governing linearised three-dimensional water wave equations to formulate a depth-averaged two-dimensional wave equation with varying wavenumber over the variable bathmetry. This is then solved by formulating a domain integral equation, solved numerically by discretisation. For a given set of geometrical and wave parameters, the bathymetry is selected by a numerical optimisation process and it is shown that the scattering cross-section is reduced towards zero with increasing refinement of the bathymetry. A fully three-dimensional boundary-element method, based on the WAMIT solver (see www.wamit.com) but adapted here to allow for depressions in the bed, is used to assess the accuracy of the mild-slope results and then further numerically optimise the bathymetry towards a cloaking structure. Numerical results provide strong evidence that perfect cloaking is possible for the fully three-dimensional problem. One practical application of the results is that cloaking implies a reduced mean drift force on the cylinder.

Extreme Waves in Sea States Crossing an Oblique Current

2010 ◽  
Author(s):  
A. Toffoli ◽  
A. V. Babanin ◽  
F. Ardhuin ◽  
M. Benoit ◽  
E. M. Bitner-Gregersen ◽  
...  
Keyword(s):  
Nonlinear Dynamics ◽  
Gravity Waves ◽  
Laboratory Experiments ◽  
Random Wave ◽  
Extreme Waves ◽  
Regular Waves ◽  
Wave Fields ◽  
Surface Gravity Waves ◽  
Directional Wave ◽  
A Current

Laboratory experiments have been carried out in the directional wave tank at Marintek (Norway) to study the nonlinear dynamics of surface gravity waves and the occurrence of extreme events, when the wave field traverses obliquely an ambient current. A condition of partial opposition has been considered. Tests on regular waves have shown that the current can trigger the formation of large amplitude waves. In random wave fields, however, this only results in a weak deviation from the statistical properties observed in absence of a current.

Acoustic radiation by ocean surface waves

2000 ◽  
Vol 415 ◽  
pp. 1-21 ◽  
Author(s):  
STEVE ARENDT ◽  
DAVID C. FRITTS
Keyword(s):  
Surface Waves ◽  
Gravity Waves ◽  
Acoustic Waves ◽  
Acoustic Radiation ◽  
Three Dimensional ◽  
Phase Speed ◽  
Ocean Surface ◽  
Surface Gravity ◽  
Ocean Surface Waves ◽  
Surface Gravity Waves

We calculate the radiation of acoustic waves into the atmosphere by surface gravity waves on the ocean surface. We show that because of the phase speed mismatch between surface gravity waves and acoustic waves, a single surface wave radiates only evanescent acoustic waves. However, owing to nonlinear terms in the acoustic source, pairs of ocean surface waves can radiate propagating acoustic waves if the two surface waves propagate in almost equal and opposite directions. We derive an analytic expression for the acoustic radiation by a pair of ocean surface waves, and then extend the result to the case of an arbitrary spectrum of ocean surface waves. We present some examples for both the two-dimensional and three-dimensional regimes. Of particular note are the findings that the efficiency of acoustic radiation increases at higher wavenumbers, and the fact that the directionality of the acoustic radiation is often independent of the shape of the spectrum.

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