scholarly journals WAVE ENERGY AND LITTORAL TRANSPORT

1964 ◽  
Vol 1 (9) ◽  
pp. 17
Author(s):  
Jose Castanho
Keyword(s):  
Wave Energy ◽  
Breaking Wave ◽  
Oblique Waves ◽  
Shore Line ◽  
Transmitted Energy ◽  
The Waves ◽  
Component Parallel

As is known the breaking of oblique waves generates currents roughly parallel to the shore line usually designated by long shore currents. The intensity of these currents which are present almost exclusively between the breaking line and the shore depends on the characteristics of the waves (angle of approach, height and period) and on the characteristics of the shore (slope and roughness). A certain amount of energy E is transmitted by the breaking wave along its direction of propagation. As this is a transmitted energy, it is possible to speak about its component parallel to the shoreline which would be indicated by E sen a , being the angle of approach of waves, i.e. the angle that crests make with the shoreline .

scholarly journals RELATIONSHIP BETWEEN ALONGSHORE WAVE ENERGY AND LITTORAL DRIFT IN THE MID-WEST COAST AT TAIWAN

1980 ◽  
Vol 1 (17) ◽  
pp. 75
Author(s):  
Ho-Shong Hou ◽  
Chung-Pan Lee ◽  
Lung-Hui Lin
Keyword(s):  
Wave Energy ◽  
Monsoon Season ◽  
Unit Length ◽  
Geographical Location ◽  
Transport Rate ◽  
High Mountain ◽  
Breaking Wave ◽  
Littoral Drift ◽  
The Relationship ◽  
The Waves

Based on the wave pattern, the geographical location and the disposition of rivers, the littoral drift moves predominantly from NE to SW direction in section II as shown in Fig. 1. Seven rivers of rapid stream bring tremendous amount of sediments from the high mountain to the nearshore of this section in typhoon season (i.e. from June to September). But for the winter monsoon season, i.e. from October to the next April, the waves induced by NE monsoons migrate littoral drift from North toward South. Applying the energy approach for unidirectional steady flow derived by Bagnold(1963), the theoretical relationship between the littoral immersed weight transport rate and the alongshore breaking wave energy is found out. It reveals that the relationship is not strictly linear, i.e. the larger part of the alongshore breaking wave energy is supplied for transporting the sediment as the former increases. But for a coast having a steady oceanographical condition, the relationship could be considered as linear relation since the alongshore breaking wave energy is not varying very much. In this paper, the study of littoral drift vs wave energy at the Taichung Coast from the Ta-Chia River to the Ta-Tu River will be carried out. Using the wave records gained by the ultrasonic wave gauge at 19m depth and the littoral drift quantity obtained from long-term observation, the relationship between alongshore breaking wave energy and littoral immersed weight transport rate is found out. First, the waves which have the same direction are summed up. Then from "THE WAVE CHARACTER COMPUTING PROGRAM", the incident directions of these wave groups at 19m depth are determined. Then the alongshore breaking wave energy per unit time per unit length of beach could be calculated by the same PROGRAM.

scholarly journals A broadbanded pressure differential wave energy converter based on dielectric elastomer generators

2021 ◽  
Author(s):  
Michele Righi ◽  
Giacomo Moretti ◽  
David Forehand ◽  
Lorenzo Agostini ◽  
Rocco Vertechy ◽  
...  
Keyword(s):  
Wave Energy ◽  
Large Deformations ◽  
Dielectric Elastomer ◽  
Wave Energy Converter ◽  
Pressure Differential ◽  
Design Stage ◽  
Small Scale ◽  
Energy Converter ◽  
Wide Range ◽  
The Waves

AbstractDielectric elastomer generators (DEGs) are a promising option for the implementation of affordable and reliable sea wave energy converters (WECs), as they show considerable promise in replacing expensive and inefficient power take-off systems with cheap direct-drive generators. This paper introduces a concept of a pressure differential wave energy converter, equipped with a DEG power take-off operating in direct contact with sea water. The device consists of a closed submerged air chamber, with a fluid-directing duct and a deformable DEG power take-off mounted on its top surface. The DEG is cyclically deformed by wave-induced pressure, thus acting both as the power take-off and as a deformable interface with the waves. This layout allows the partial balancing of the stiffness due to the DEG’s elasticity with the negative hydrostatic stiffness contribution associated with the displacement of the water column on top of the DEG. This feature makes it possible to design devices in which the DEG exhibits large deformations over a wide range of excitation frequencies, potentially achieving large power capture in a wide range of sea states. We propose a modelling approach for the system that relies on potential-flow theory and electroelasticity theory. This model makes it possible to predict the system dynamic response in different operational conditions and it is computationally efficient to perform iterative and repeated simulations, which are required at the design stage of a new WEC. We performed tests on a small-scale prototype in a wave tank with the aim of investigating the fluid–structure interaction between the DEG membrane and the waves in dynamical conditions and validating the numerical model. The experimental results proved that the device exhibits large deformations of the DEG power take-off over a broad range of monochromatic and panchromatic sea states. The proposed model demonstrates good agreement with the experimental data, hence proving its suitability and effectiveness as a design and prediction tool.

scholarly journals Nonlinear wave energy modelling in the surf zone

1996 ◽  
Vol 3 (2) ◽  
pp. 127-134 ◽  
Author(s):  
Th. V. Karambas
Keyword(s):  
Wave Energy ◽  
Surf Zone ◽  
Energy Balance Equation ◽  
Propagation Model ◽  
Breaking Wave ◽  
Dissipation Term ◽  
Energy Modelling ◽  
Turbulence Effects ◽  
Energy And Momentum ◽  
Energy Equations

Abstract. Breaking wave energy in the surf zone is modelled through the incorporation of the time dependent energy balance equation in a non linear dispersive wave propagation model. The energy equations solved simultaneously with the momentum and continuity equation. Turbulence effects and the non uniform horizontal velocity distribution due to breaking is introduced in both the energy and momentum equations. The dissipation term is a function of the velocity defect derived from a turbulent analysis. The resulting system predicts both wave characteristics (surface elevation and velocity) and the energy distribution inside surf zone. The model is validated against experimental data and analytical expressions.

‘Inverse’ Concept: Wave Energy Generation by Motion and Green Water Maximisation

2009 ◽  
Author(s):  
Bas Buchner ◽  
Frederick Jaouen
Keyword(s):  
Renewable Energy ◽  
Energy Conversion ◽  
Frequency Domain ◽  
Water Flow ◽  
Wave Energy ◽  
Volume Of Fluid ◽  
Green Water ◽  
Wave Energy Conversion ◽  
Energy Concept ◽  
The Waves

This paper presents the initial investigations into the ‘Inverse’ concept for wave energy conversion, based on the maximisation of motions and green water. The ‘Inverse’ concept combines aspects of ‘overtopping’, ‘heaving’ and ‘pitching’ wave energy conversion concepts, but also adds specific aspects such as the use of green water. Instead of reducing the motions and green water as is done in normal offshore hydrodynamics, the ‘Inverse’ concepts tries to maximise the motions and green water to generate energy from the waves. Results are presented of frequency domain calculations for the motion (de-) optimisation. Improved Volume Of Fluid (iVOF) simulations are used to simulate the green water flow on the deck. It is concluded that the potential of the ‘Inverse’ concept is clear. As a result of the double connotation of the word ‘green’, this renewable energy concept could also be called the ‘green water’ concept. Further work needs to be carried out on the further optimisation of the concept.

Studies of Extreme Energy Localizations With Smoothed Particle Hydrodynamics

2015 ◽  
Author(s):  
Ayan Moitra ◽  
Christopher Chabalko ◽  
Balakumar Balachandran
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Ocean Waves ◽  
Breaking Wave ◽  
Wave Focusing ◽  
Wave Interference ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Wave Heights ◽  
The Waves ◽  
Wave Phenomena

Smoothed particle hydrodynamics (SPH) is used to simulate hydrodynamic waves and wave phenomena including focusing from wave interference. This Lagrangian based method can be used to naturally simulate hydrodynamic free surfaces, including the free surface of a breaking wave. A virtual wave tank is simulated where wave motions can be excited from either side. Wave focusing is observed at the tank center, where the waves interfere. As a measure of the interference, the wave heights that result from focusing are presented. Certain types of wave focusing are thought to lead to large ocean waves. The efficacy of SPH in modeling wave focusing is critical to further understanding and predicting extreme wave phenomena with SPH.

scholarly journals Investigating the damping rate of phase-mixed Alfvén waves

2019 ◽  
Vol 632 ◽  
pp. A93 ◽  
Author(s):  
A. P. K. Prokopyszyn ◽  
A. W. Hood
Keyword(s):  
Wave Energy ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Coronal Loops ◽  
Phase Mixing ◽  
Heating Mechanism ◽  
At Resonance ◽  
Damping Rate ◽  
Field Lines ◽  
The Waves

Context. This paper investigates the effectiveness of phase mixing as a coronal heating mechanism. A key quantity is the wave damping rate, γ, defined as the ratio of the heating rate to the wave energy. Aims. We investigate whether or not laminar phase-mixed Alfvén waves can have a large enough value of γ to heat the corona. We also investigate the degree to which the γ of standing Alfvén waves which have reached steady-state can be approximated with a relatively simple equation. Further foci of this study are the cause of the reduction of γ in response to leakage of waves out of a loop, the quantity of this reduction, and how increasing the number of excited harmonics affects γ. Methods. We calculated an upper bound for γ and compared this with the γ required to heat the corona. Analytic results were verified numerically. Results. We find that at observed frequencies γ is too small to heat the corona by approximately three orders of magnitude. Therefore, we believe that laminar phase mixing is not a viable stand-alone heating mechanism for coronal loops. To arrive at this conclusion, several assumptions were made. The assumptions are discussed in Sect. 2. A key assumption is that we model the waves as strictly laminar. We show that γ is largest at resonance. Equation (37) provides a good estimate for the damping rate (within approximately 10% accuracy) for resonant field lines. However, away from resonance, the equation provides a poor estimate, predicting γ to be orders of magnitude too large. We find that leakage acts to reduce γ but plays a negligible role if γ is of the order required to heat the corona. If the wave energy follows a power spectrum with slope −5/3 then γ grows logarithmically with the number of excited harmonics. If the number of excited harmonics is increased by much more than 100, then the heating is mainly caused by gradients that are parallel to the field rather than perpendicular to it. Therefore, in this case, the system is not heated mainly by phase mixing.

A New Design of Dual-Channel Wave Energy Power Device

2014 ◽  
Vol 602-605 ◽  
pp. 2878-2880
Author(s):  
Chun Yi Huang
Keyword(s):  
Wave Energy ◽  
Mechanical Energy ◽  
Ocean Wave ◽  
Ocean Energy ◽  
Dual Channel ◽  
Ocean Wave Energy ◽  
Channel Wave ◽  
Working Principle ◽  
Improved Design ◽  
The Waves

Ocean energy is a precious pearl. However, in the exploitation of the sea of people, the available development of ocean wave energy method is too simple and the structure of the device is relatively complex. This paper examines the analysis for the direction of the waves along the coast, and designed a dual-channel ocean wave energy generation device as well as having made a detailed description of its structure and concrete working principle. The ingenious engineering design of the device can continuously generate electricity. As the waves of high and low tides will produce mechanical energy to drive the rotation of the impeller, the improved design in this paper make full use of this principle so that can produce a steady stream of electricity. Due to the inherent advantages of this device, it has great room for improvement and broad application prospects.

Wave-Follower Field Measurements of the Wind-Input Spectral Function. Part III: Parameterization of the Wind-Input Enhancement due to Wave Breaking

2007 ◽  
Vol 37 (11) ◽  
pp. 2764-2775 ◽  
Author(s):  
Alexander V. Babanin ◽  
Michael L. Banner ◽  
Ian R. Young ◽  
Mark A. Donelan
Keyword(s):  
Energy Flux ◽  
Water Waves ◽  
Wave Breaking ◽  
Field Measurements ◽  
Mean Value ◽  
Breaking Wave ◽  
Strong Wind ◽  
Local Wave ◽  
Wind Input ◽  
The Waves

Abstract This is the third in a series of papers describing wave-follower observations of the aerodynamic coupling between wind and waves on a large shallow lake during the Australian Shallow Water Experiment (AUSWEX). It focuses on the long-standing problem of the aerodynamic consequences of wave breaking on the wind–wave coupling. Direct field measurements are reported of the influence of wave breaking on the wave-induced pressure in the airflow over water waves, and hence the energy flux to the waves. The level of forcing, measured by the ratio of wind speed to the speed of the dominant (spectral peak) waves, covered the range of 3–7. The propagation speeds of the dominant waves were limited by the water depth and the waves were correspondingly steep. These measurements allowed an assessment of the magnitude of any breaking-induced enhancement operative for these field conditions and provided a basis for parameterizing the effect. Overall, appreciable levels of wave breaking occurred for the strong wind forcing conditions that prevailed during the observational period. Associated with these breaking wave events, a significant phase shift is observed in the local wave-coherent surface pressure. This produced an enhanced wave-coherent energy flux from the wind to the waves with a mean value of 2 times the corresponding energy flux to the nonbreaking waves. It is proposed that the breaking-induced enhancement of the wind input to the waves can be parameterized by the sum of the nonbreaking input and the contribution due to the breaking probability.

Self-induced waves in a conduit with corrugated walls, I. Experiments with water in an open horizontal channel with vertically corrugated sides

1960 ◽  
Vol 259 (1296) ◽  
pp. 18-27 ◽  
Keyword(s):  
Critical Velocity ◽  
Higher Order ◽  
Horizontal Channel ◽  
Shore Line ◽  
The Waves

The walls of a rectangular horizontal channel, the bottom of which was smooth, were lined with corrugated iron arranged to give a shore line of alternate bays and capes. When water passed through the channel with a well-marked critical velocity, a continuous train of self-induced waves was formed on the surface, and moved steadily upstream into the contraction which led from the supply reservoir. With a narrow stream the waves possessed horizontal transverse crests and troughs, but above a certain width the waves were antisymmetrical. With different combinations of channels and corrugations, the mechanism was examined by which energy was taken from the stream to maintain the waves. Linings of rectangular capes and bays produced higher-order waves, and the effect was largely independent of the number of bays.

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