Surface-wave propagation over sinusoidally varying topography

1984 ◽  
Vol 144 ◽  
pp. 419-443 ◽  
Author(s):  
A. G. Davies ◽  
A. D. Heathershaw
Keyword(s):  
Reflection Coefficient ◽  
Surface Waves ◽  
Wave Field ◽  
Incident Wave ◽  
Wave Energy ◽  
Bottom Topography ◽  
Finite Depth ◽  
Linear Perturbation ◽  
Linear Perturbation Theory ◽  
Incident Wave Energy

Surface waves travelling in water of finite depth may be scattered by a region of undulating bottom topography. The present study is concerned with the idealized two-dimensional situation in which long-crested surface waves are incident upon a patch of long-crested regular bottom ripples. The principal question examined concerns the amount of incident wave energy that is reflected by the ripple patch. Linear perturbation theory is used to show that the reflection coefficient is both oscillatory in the quotient of the length of the patch and the surface wavelength, and also strongly dependent upon the quotient of the surface and bed wavelengths. In particular, there is a Bragg resonance between the surface waves and the ripples, which is associated with the reflection of incident wave energy. A secondary question concerns the nature of the wave field in the immediate vicinity of the ripple patch. In resonant cases, it is shown how the partially standing wave on the upwave side of the ripple patch gives way, in an almost linear manner over the patch itself, to a progressive transmitted wave on the downwave side. The theoretical predictions are compared with an extensive set of laboratory observations made in a wave tank. Comparisons relating both to the reflection coefficient, and also to the wave field over the ripple patch, are shown to give consistently good agreement. Finally, the implications of the results for sediment transport on an erodible bed are examined.

scholarly journals WAVE REFLECTION GENERATED BY CAISSONS WITH INTERNAL RUBBLE MOUND OF VARIABLE SLOPE

2012 ◽  
Vol 1 (33) ◽  
pp. 51 ◽  
Author(s):  
Carla Faraci ◽  
Biagio Cammaroto ◽  
Luca Cavallaro ◽  
Enrico Foti
Keyword(s):  
Optimal Design ◽  
Reflection Coefficient ◽  
Analytical Model ◽  
Incident Wave ◽  
Wave Energy ◽  
Wave Reflection ◽  
Energy Reduction ◽  
Experimental Campaign ◽  
Rubble Mound ◽  
Incident Wave Energy

The paper reports on an experimental campaign focused on the performances of prefabricated caissons with internal rubble mound (combined caissons) in terms of incident wave energy reduction. The frontal opening and the chamber width of the caisson were changed in order to find the optimal design dimensions allowing the reflection coefficient to be reduced as much as possible. As expected, the best performances of the combined caisson occur when the rubble mound slope is gentler. The experimental results were also compared with an analytical model available in literature; such a comparison showed that the combined caisson exhibits a smaller reflection than predicted as far as wave periods higher than 8-9 s at a prototype scale are concerned.

Evaluation of Incident Wave Energy in Flume Tests

1987 ◽  
Author(s):  
Eliezer Kit ◽  
Oded Gottlieb ◽  
Dov S. Rosen
Keyword(s):  
Incident Wave ◽  
Wave Energy ◽  
Flume Tests ◽  
Incident Wave Energy

scholarly journals A Novel Method for Estimating Wave Energy Converter Performance in Variable Bathymetry Regions and Applications

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2092 ◽  
Author(s):  
Kostas Belibassakis ◽  
Markos Bonovas ◽  
Eugen Rusu
Keyword(s):  
Wave Field ◽  
Wave Energy ◽  
Water Waves ◽  
Bottom Topography ◽  
Wave Energy Converter ◽  
Diffraction Radiation ◽  
Floating Bodies ◽  
Energy Converter ◽  
Coupled Mode ◽  
Energy Absorbers

A numerical model is presented for the estimation of Wave Energy Converter (WEC) performance in variable bathymetry regions, taking into account the interaction of the floating units with the bottom topography. The proposed method is based on a coupled-mode model for the propagation of the water waves over the general bottom topography, in combination with a Boundary Element Method for the treatment of the diffraction/radiation problems and the evaluation of the flow details on the local scale of the energy absorbers. An important feature of the present method is that it is free of mild bottom slope assumptions and restrictions and it is able to resolve the 3D wave field all over the water column, in variable bathymetry regions including the interactions of floating bodies of general shape. Numerical results are presented concerning the wave field and the power output of a single device in inhomogeneous environment, focusing on the effect of the shape of the floater. Extensions of the method to treat the WEC arrays in variable bathymetry regions are also presented and discussed.

scholarly journals FIELD EXPERIMENT ON BEACH GRAVEL TRANSPORT

1978 ◽  
Vol 1 (16) ◽  
pp. 101 ◽  
Author(s):  
Masataro Hattori ◽  
Takasuke Suzuki
Keyword(s):  
Field Experiment ◽  
Incident Wave ◽  
Wave Energy ◽  
Transport Processes ◽  
Central Japan ◽  
Selective Transport ◽  
Longshore Transport ◽  
Wave Energy Flux ◽  
The Mean ◽  
Incident Wave Energy

To examine the longshore transport processes of beach gravels under wave action, a field experiment was performed by tracing the dacite blocks injected on Fuji Coast, Shizuoka Prefecture, Central Japan. The mean dislocating velocity of the tracer was 2 to 3 m/day under normal sea conditions, while under storm conditions it reached about 400 m/day. This -velocity was fairly proportional to the longshore component of incident wave energy flux. The longshore variations of the size and shape of beach gravels were mainly resulted from the progressive attrition and impact breakage of beach gravels rather than from the selective transport.

Do longshore bars shelter the shore?

2000 ◽  
Vol 404 ◽  
pp. 251-268 ◽  
Author(s):  
JIE YU ◽  
CHIANG C. MEI
Keyword(s):  
Spatial Distribution ◽  
Incident Wave ◽  
Wave Energy ◽  
Phase Relation ◽  
Bragg Reflection ◽  
Qualitative Change ◽  
Numerical Calculations ◽  
Reflected Waves ◽  
Incident Waves ◽  
Incident Wave Energy

In most past theories on Bragg reflection of waves by a finite patch of rigid bars, only outgoing waves are allowed on the transmission side, simulating the effect of an idealized shoreline where all the incident wave energy is consumed by breaking. In these theories the amplitudes of both the incident and reflected waves are found to decrease monotonically over the bar patch in the shoreward direction. This result has motivated the idea of artificially constructing bars to protect a beach from incident waves. However, some numerical calculations have suggested that this tendency does not always hold when there is some reflection from the shore. We show here that with finite reflection by the shoreline the spatial distribution of wave energy over the patch can indeed be reversed, indicating that the mechanism can increase the hazards to the beach. The phase relation between the bars and the shoreline reflection is found to be the key to this qualitative change of wave response.

scholarly journals PROBLEMS OF SEDIMENTS TRANSPORT MODELING IN THE COASTAL AREA

2021 ◽  
Vol 49 (1) ◽  
pp. 93-141
Author(s):  
R. D. Kosyan ◽  
B. V. Divinsky
Keyword(s):  
Sediment Transport ◽  
Surface Waves ◽  
Wave Field ◽  
Frequency Distribution ◽  
Coastal Zone ◽  
Bottom Sediments ◽  
Wave Energy ◽  
Laboratory Experiments ◽  
Wind Waves ◽  
Wave Spectrum

Due to the development of measuring instruments, a more detailed analysis of the wave field and the field of suspended sediments spatio-temporal characteristics has become possible. Through the efforts of Russian specialists over the past decades: A unique database of observations of the sediment movement in storm situations in different physical and geographical areas of the coastal zone of the Black, Baltic, North, Mediterranean, South China Seas has been collected, supplemented by extensive data of laboratory experiments in the best laboratory in Europe (Hannover, Germany). New experimental material has been obtained to determine the physical features of sediment transport by wave flow. The main mechanisms controlling the amplitude and phase relationships of the concentration fluctuations and discharge of suspended sediment on time scales less than the period of the peak of the wind wave spectrum are considered. The presence of low-frequency fluctuations in sediment concentration with a period of the order of several periods of wind waves and an amplitude several times higher than the average value of concentration is noted. The previously unexplored problem of the wave energy frequency distribution in the spectrum of surface waves influence on the sediment transport has been analyzed. Differences in the response of the washed-out bottom to an external disturbance, represented by irregular surface waves with constant integral characteristics (significant wave height and period of the spectrum peak) and variable wave energy frequency distribution, were revealed. The influence of swell waves on the redistribution of bottom sediments in the sea coastal zone was investigated. It is shown that dividing the wave field into separate components allows a more correct description of the spatiotemporal structure of surface waves, as well as a significant refinement of the bottom sediment transport schemes in the coastal zone. Using the example of the Anapa bay bar, it is shown that situations are possible in which the alongshore flow of bottom sediments is almost completely determined by swell waves. The results of field and laboratory experiments make it possible to determine the directions for further research on the creation of physically based models of sediment transport by waves and wave currents.

scholarly journals RESEARCHES ON SEA-WALLS

1970 ◽  
Vol 1 (12) ◽  
pp. 88
Author(s):  
S. Nagal
Keyword(s):  
Incident Wave ◽  
Wave Energy ◽  
Precast Concrete ◽  
Recent Decade ◽  
Point Of View ◽  
Industrial Firms ◽  
Wave Overtopping ◽  
Port Facilities ◽  
Sea Wall ◽  
Incident Wave Energy

In the recent decade, very wide areas of sea where the depths of water are from several meters to ten meters or more during storms have been reclaimed for industrial firms and port facilities in many places in Japan As the incident wave energy in such cases is very large at the sea-walls, the protection of the reclaimed lands from wave overtopping by the conventional sea-walls of vertical type or composite-slope«and-berai type is generally impossible from an economical point of view In Japan a special type of sea-wall, which is of such a type that a rubble-mound covered with specially shaped precast concrete armor blocks is built in front of the sea-wall to absorb most of the incident wave energy, has been constructed to protect the reclaimed lands from wave overtopping Most of the seawalls have been proved satisfactory after passing of typhoons over or near the sea-walls The design of the sea-walls is presented here in by showing the comparisons between the experiments and prototypes during typhoons.

Model Experiment on an OWC-Type Wave-Energy Converter With Hydraulic Power Take-Off

2002 ◽  
Author(s):  
Torkel Bjarte-Larsson ◽  
Per Magne Lillebekken ◽  
Jo̸rgen Hals ◽  
Johannes Falnes
Keyword(s):  
Incident Wave ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Laboratory Model ◽  
Energy Converter ◽  
Hydraulic Power ◽  
Optimum Load ◽  
Wave Channel ◽  
Period 2 ◽  
Incident Wave Energy

A wave-energy converter of the OWC type is described, in which the absorbed wave energy is converted to useful energy by means of a hydraulic power take-off. Means are provided to enable the float to be latched for phase control. The float is connected to a piston pump, which pumps water from the level of the water in the wave channel to a higher level, which is adjustable. By means of measurements from three wave gauges (two on the upstream side and one on the downstream side) the incident wave energy and the absorbed wave energy are derived. For a down-scaled laboratory model, resonance is obtained with an incident sinusoidal wave of period 1 s. With optimum load, the converted useful hydraulic energy is a fraction of 0.2 of the incident wave energy. The absorbed wave energy is then 0.6 units of the incident wave energy. With wave period 2 s and optimum load, these energy fractions are 0.03 and 0.13, which are increased to 0.05 and 0.21, respectively, when latching control is applied.

Regularly-spaced grooves on shore platforms in north Northumberland, UK

2020 ◽  
Vol 63 (2) ◽  
pp. 124-134
Author(s):  
Alison M. Tymon ◽  
Barry G. Tymon
Keyword(s):  
Incident Wave ◽  
Wave Energy ◽  
Surf Zone ◽  
High Water ◽  
Edge Waves ◽  
Shore Platform ◽  
Bedding Planes ◽  
High Water Mark ◽  
Incident Wave Energy ◽  
Shore Platforms

Unusual regularly-spaced grooves are found between low water mark (LWM) and high water mark (HWM) on several shore platforms in north Northumberland. References in the literature are sparse, so data were collected to establish the nature of the grooves and to elucidate the processes that might have formed them. Groove formation is confined to strata with widely spaced bedding planes on shore platforms dipping at no more than 5° towards the sea. The grooves are symmetrical, bifurcation is common and grooves on sandstones are deeper and more sinuous than those on limestones. Grooves at mid-tide levels are wider than grooves near LWM and HWM and the trend of the grooves is not related to joint trends. The process that has formed the characteristically smooth surfaces of the grooves is considered to be abrasion by sand and pebbles carried by waves in the surf zone of the shore platform. The width of the grooves is remarkably regular, and it is suggested that this may be due to the effects of the increase in incident wave energy given by edge waves.

scholarly journals EVALUATION OF INCIDENT WAVE ENERGY IN FLUME TEST

1986 ◽  
Vol 1 (20) ◽  
pp. 93
Author(s):  
Eliezer Kit ◽  
Oded Gottlieb ◽  
Dov S. Rosen
Keyword(s):  
Least Squares ◽  
Incident Wave ◽  
Wave Energy ◽  
Least Squares Method ◽  
Stationary Wave ◽  
Residual Energy ◽  
Irregular Waves ◽  
Wave Spectra ◽  
Reflected Wave ◽  
Incident Wave Energy

A two dimensional model study, carried out for a structure in a flume using irregular waves, presents the problem of determining the relationship between the total incident wave energy attacking the structure and its response to that attack (displacements, forces, etc.) in various sea states, The total incident wave energy can be evaluated indirectly only, because the wave energy measured in the flume contains an extent of residual wave energy in addition to that generated by the wave machine. This residual energy consists of the re-reflected wave energy from the paddle of the wave machine, assuming the existence of quasi-stationary wave conditions in the flume. A method originally presented by Gravesen et al. (1974), was applied in this study to evaluate the total incident wave energy. In view of the results obtained by this method, a physically more sound refinement is proposed for the evaluation of the total incident wave energy (and characteristic wave height). Results of model tests were analyzed by the CAMERI refinement and compared with the Gravesen method and with a cross-spectral least squares method, separating incident and reflected wave spectra from wave spectra measured in the flume, Good agreement was found between the results obtained employing the CAMERI refinement and the cross-spectral least squares method, Advantages and drawbacks of these methods are indicated,

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