scholarly journals USE OP CRENULATE SHAPED BAYS TO STABILIZE COASTS

1972 ◽  
Vol 1 (13) ◽  
pp. 70 ◽  
Author(s):  
Richard Silvester ◽  
Siew-Koon Ho
Keyword(s):  
Wave Energy ◽  
Logarithmic Spiral ◽  
Stages Of Development ◽  
Littoral Drift ◽  
Approach Angle ◽  
Specific Relationship ◽  
The Waves ◽  
Resultant Wave

Crenulate shaped bays are the rule rather than the exception on coastal margins of oceans, inland seas or lakes where sedimentary beaches exist between headlands. They have a particular orientation to the swell or resultant wave energy vector, such that the straight tangent section is downcoast and the curved portion upcoast. The latter is a logarithmic spiral at all stages of development of the bay. When fully stable, that is no littoral drift taking place, the constant of the log-spiral equation has a specific relationship to the approach angle of the waves to the headland alignment. In this condition it is shown that diffraction and refraction are involved when waves sculpture the curved beach in the lee of the upcoast headland. A further ratio to identify stable bays appears to be the ratio of indentation length to clearance between headlands. The application of crenulate shaped bays to stabilization of a reclaimed shoreline suffering strong littoral drift on Singapore Island is described.

scholarly journals BEACH DEVELOPMENT BETWEEN HEADLAND BREAKWATERS IN A LOW WAVE ENERGY ENVIRONMENT, PASIR RIS, SINGAPORE

1986 ◽  
Vol 1 (20) ◽  
pp. 76
Author(s):  
S.Y. Chew ◽  
S.K. Ho ◽  
P.P. Wong ◽  
Y.Y. Leong
Keyword(s):  
Wave Energy ◽  
Logarithmic Spiral ◽  
Wave Action ◽  
Sediment Supply ◽  
Entire Length ◽  
Littoral Drift ◽  
Wave Approach ◽  
Model Study ◽  
Energy Environment ◽  
Permanent Shape

One of the function of the offshore breakwater is to protect the coast from wave action. By dissipating the wave energy along its entire length, the breakwater causes sediments in its lee to deposit and a shore salient is formed. If the offshore breakwater are placed in a series along a coast with a gentle offshore slope and a substantial littoral drift tombolo will form behind the breakwaters between which bays will be sculptured by waves to form stable shapes (1). These attached breakwater would thus form a series of artificial headlands. In nature, beaches between headlands are influenced by the position of the headlands. Where the headlands are closely spaced and a limited sediment supply exists, small pockets beaches are formed. Where the headlands are far apart and an adequate sediment supply exists, long and wide beaches are formed. Generally, between these two extremes most beaches between natural headlands take a shape that is related to the predominant wave approach; on the downcoast sector is a long and straight beach, while on the upcoast end is curbed beach. Silvester (2) in his model study established a relationship between the logarithmic spiral constant ( °^ ) and the angle of predominant wave approach ( & ). A quasi-permanent shape was reached when waves broke simultaneously around the model bay. As it is difficult to measure the curve sector in nature, Silvester and Ho (3) suggested the use of an indentation ratio to relate the bay's shape to wave approach.

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.

‘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.

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.

scholarly journals Numerical Study on the Optimization of Hydrodynamic Performance of Oscillating Buoy Wave Energy Converter

2021 ◽  
Vol 28 (1) ◽  
pp. 48-58
Author(s):  
Wenbin Lai ◽  
Yonghe Xie ◽  
Detang Li
Keyword(s):  
Wave Energy ◽  
Numerical Study ◽  
Energy Conversion Efficiency ◽  
Absorption Efficiency ◽  
Wave Energy Converter ◽  
Hydrodynamic Performance ◽  
Energy Converter ◽  
Physical Experiments ◽  
Working Principle ◽  
The Waves

Abstract The oscillating buoy wave energy converter (OBWEC) captures wave energy through the undulating movement of the buoy in the waves. In the process of capturing wave energy, the hydrodynamic performance of the buoy plays an important role. This paper designed the “Haida No. 1” OBWEC, in which the buoy adopts a form of swinging motion. In order to further improve the hydrodynamic performance of the buoy, a 2D numerical wave tank (NWT) model is established using ADINA software based on the working principle of the device. According to the motion equation of the buoy in the waves, the influence of the buoy shape, arm length, tilt angle, buoy draft, buoy width, wave height and Power Take-off (PTO) damping on the hydrodynamic performance of the buoy is studied. Finally, a series of physical experiments are performed on the device in a laboratory pool. The experimental results verify the consistency of the numerical results. The research results indicate that the energy conversion efficiency of the device can be improved by optimizing the hydrodynamic performance of the buoy. However, the absorption efficiency of a single buoy for wave energy is limited, so it is very difficult to achieve full absorption of wave energy.

scholarly journals KNSwing—On the Mooring Loads of a Ship-Like Wave Energy Converter

2019 ◽  
Vol 7 (2) ◽  
pp. 29
Author(s):  
Kim Nielsen ◽  
Jonas Thomsen
Keyword(s):  
Numerical Model ◽  
Wave Energy ◽  
Numerical Models ◽  
Breaking Waves ◽  
Wave Energy Converter ◽  
Experimental Results ◽  
Irregular Waves ◽  
Mooring System ◽  
Energy Converter ◽  
The Waves

The critical function of keeping a floating Wave Energy Converter in position is done by a mooring system. Several WECs have been lost due to failed moorings, indicating that extreme loads, reliability and durability are very important aspects. An understanding of the interaction between the WEC’s motion in large waves and the maximum mooring loads can be gained by investigating the system at model scale supported by numerical models. This paper describes the testing of a novel attenuator WEC design called KNSwing. It is shaped like a ship facing the waves with its bow, which results in low mooring loads and small motions in most wave conditions when the structure is longer than the waves. The concept is tested using an experimental model at scale 1:80 in regular and irregular waves, moored using rubber bands to simulate synthetic moorings. The experimental results are compared to numerical simulations done using the OrcaFlex software. The experimental results show that the WEC and the mooring system survives well, even under extreme and breaking waves. The numerical model coefficient concerning the nonlinear drag term for the surge motion is validated using decay tests. The numerical results compare well to the experiments and, thereby, the numerical model can be further used to optimize the mooring system.

Numerical Modeling and Evaluation of Wave Energy Converters

2009 ◽  
Author(s):  
Heather Peng ◽  
Wei Qiu ◽  
Don Spencer
Keyword(s):  
Numerical Modeling ◽  
Frequency Domain ◽  
Wave Energy ◽  
Energy Production ◽  
Wave Power ◽  
Power Absorption ◽  
Wave Energy Converters ◽  
Numerical Studies ◽  
The Waves ◽  
Energy Converters

Wave energy converters use the motion of floating or submerged bodies to extract energy from the waves. Power absorption can be simulated using a simple linear damper with a resistance to motion which is proportional to velocity. Because of the interaction between energy production and motion, there will be an optimum rate of energy production for each wave frequency. Too much damping or too little damping can cause little energy produced. The wave absorption range also depends on the tuned frequency. In this paper, the maximum rates of energy absorption for submerged and floating wave energy converters are evaluated by employing the panel-free method for the motions of the converters in the frequency domain. A general expression for the wave power absorption is described. Numerical studies show that the optimal energy efficiencies of wave energy converters can be well predicted by employing the panel-free method for motion computations.

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