scholarly journals EFFECTS OF NONUNIFORM WAVE ENERGY IN THE LITTORAL ZONE

1970 ◽  
Vol 1 (12) ◽  
pp. 47
Author(s):  
Victor Goldsmith ◽  
Joseph M. Colonell
Keyword(s):  
Wave Energy ◽  
Beach Erosion ◽  
Cape Cod ◽  
Beach Profile ◽  
Wave Refraction ◽  
Close Relationship ◽  
Erosion And Accretion ◽  
Ebb Tidal Delta ◽  
The Waves ◽  
Nonuniform Wave

Bi-weekly monitoring of four closely-spaced permanent beach profile stations located on the northeast end of Monomoy Island (Cape Cod) has revealed major variations in the amount of erosion and accretion occurring along this portion of the Massachusetts shoreline During the 27-month monitoring period a close relationship was observed between changes in the beach and offshore portions of the profiles Three distinct types of bars were noted (1) Subtidal bars which are parallel to the shoreline and located one to two thousand feet off those portions of the shoreline undergoing relatively small amounts of beach erosion, (2) Subtidal bars which are perpendicular to the shoreline and attached to areas of the shore undergoing large amounts of erosion, and (3) Large intertidal bars which are oriented obliquely to the shoreline and associated with the formation of the ebb-tidal delta and the resulting wave refraction patterns The large variations in erosion and accretion occurring along the beach at any one time are related to the nonumform distribution of energy within the waves arriving at this section of the coastline This nonunifortuity of wave energy is attributed to refraction of the waves around the irregular bathymetry offshore from Monomoy, and it appears to produce shoreline protuberances of sand which are flanked updrift and downdrift by erosional zones.

scholarly journals THE RELATIONSHIP BETWEEN WAVE ACTION AND BEACH PROFILE CHARACTERISTICS

2011 ◽  
Vol 1 (7) ◽  
pp. 14 ◽  
Author(s):  
P.H. Kemp
Keyword(s):  
Rational Design ◽  
Break Point ◽  
Coarse Sand ◽  
Beach Erosion ◽  
Beach Profile ◽  
Model Study ◽  
Materials Used ◽  
Profile Characteristics ◽  
The Relationship ◽  
The Waves

The rational design of coast protection works requires a knowledge of the behaviour of the beach under natural conditions. The understanding of the relationship between the waves acting on the beach and the characteristics of the beach profile produced, is thus a necessary preliminary to the analysis of the causes of beach erosion and the evaluation of the effect of projected remedial measures. The present paper describes the results of a series of preliminary hydraulic model experiments carried out by the author prior to a model study of the behaviour of groynes in stabilising beaches. Most of the beach materials used represented coarse sand or shingle in nature. The results demonstrate the fundamental importance of the "phase difference" in terms of wave period between the break-point and the limit of uprush, in relation to flow conditions, cusp formation, and the change from "step" to "bar" type profiles. Within the limits of the experiments an expression connecting the breaker height, beach profile length, and grain diameter is developed, and its implications examined in relation to beach slope, and to the previous "wave steepness" criterion for the change from step to bar type profiles. Observations are included on the rate of recession of a shoreline due to the onset of more severe wave conditions.

scholarly journals EROSION AND ACCRETION ON CURVED BEACH

2012 ◽  
Vol 1 (33) ◽  
pp. 11 ◽  
Author(s):  
Kideok Do ◽  
Nobuhisa Kobayashi ◽  
Kyung-Duck Suh
Keyword(s):  
Beach Erosion ◽  
Sand Transport ◽  
Beach Profile ◽  
Severe Storms ◽  
Mean Sea Level ◽  
Longshore Sediment Transport ◽  
Multiple Cross ◽  
Median Diameter ◽  
Erosion And Accretion ◽  
The Mean

The performance of a large nourishment project on Bethany Beach, Delaware is evaluated using available beach profile, wave and tide data during September 2007 to September 2010. The volume of the placed sand with the median diameter of 0.31 mm was about 500 m3/m along the curved shoreline of 1.8 km length. The nourished beach was attacked by two severe storms in May 2008 and November 2009. The eroded sand volume above the mean sea level (MSL) was about 70 m3/m for each of the two storms and emergency repairs were necessary. The numerical cross-shore model with multiple cross-shore lines is used to compute the cross-shore and longshore sediment transport. The beach erosion above MSL is shown to be caused by the offshore sand transport and the alongshore gradient of the longshore sand transport rate. The performance of the nourished beach is predicted to be sensitive to the sand diameter in the range of 0.23 to 0.45 mm.

UNDERWATER BARRED BEACH PROFILE TRANSFORMATION UNDER DIFFERENT WAVES CONDITIONS

2017 ◽  
Author(s):  
Olga Kuznetsova ◽  
Olga Kuznetsova ◽  
Yana Saprykina ◽  
Yana Saprykina ◽  
Boris Divinsky ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Coastal Zone ◽  
Wave Height ◽  
Wave Energy ◽  
Wave Period ◽  
Beach Profile ◽  
Infragravity Waves ◽  
Wave Parameters ◽  
Mean Wave Period

Based on numerical modelling evolution of beach under waves with height 1,0-1,5 m and period 7,5 and 10,6 sec as well as spectral wave parameters varying cross-shore analysed. The beach reformation of coastal zone relief is spatially uneven. It is established that upper part of underwater beach profile become terraced and width of the terrace is in direct pro-portion to wave height and period on the seaward boundary but inversely to angle of wave energy spreading. In addition it was ascertain that the greatest transfiguration of profile was accompanied by existence of bound infragravity waves, smaller part of its energy and shorter mean wave period as well as more significant roller energy.

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 An Analysis of Shoreline Changes Using Combined Multitemporal Remote Sensing and Digital Evaluation Model

2020 ◽  
Vol 6 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Dao Dinh Cham ◽  
Nguyen Thai Son ◽  
Nguyen Quang Minh ◽  
Nguyen Tien Thanh ◽  
Tran Tuan Dung
Keyword(s):  
Remote Sensing ◽  
Multiple Scales ◽  
Evaluation Model ◽  
Beach Erosion ◽  
Shoreline Evolution ◽  
The North ◽  
Digital Evaluation ◽  
Significant Difference ◽  
Erosion And Accretion ◽  
Multitemporal Remote Sensing

Cua Dai estuary belonged to Quang Nam province is considered to be one of the localities of Vietnam having a complex erosion and accretion process. In this area, sandbars are recently observed with lots of arguments about the causes and regimes of formation. This could very likely result of not reliable source of information on shoreline evolution and a lack of historical monitoring data. Accurately identification of shoreline positions over a given period of time is a key to quantitatively and accurately assessing the beach erosion and accretion. The study is therefore to propose an innovative method of accurately shoreline positions for an analysis of coastal erosion and accretion in the Cua Dai estuary. The proposed technology of multitemporal remote sensing and digital evaluation model with tidal correction are used to analyse the changes in shoreline and estimate the rate of erosion and accretion. An empirical formula is, especially, exposed to fully interpret the shoreline evolution for multiple scales based on a limitation of satellite images during 1965 to 2018. The results show that there is a significant difference of shoreline shift between corrections and non-corrections of tidal. Erosion process tends to be recorded in the Cua Dai cape located in the Cua Dai ward, especially in the An Luong cape located in the Duy Hai commune with the length of 1050 m. Furthermore, it is observed that there is much stronger erosion in the north side compared with south side of Cua Dai estuary.

‘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 BEACH PROFILES AT TORREY PINES, CALIFORNIA

1976 ◽  
Vol 1 (15) ◽  
pp. 75 ◽  
Author(s):  
David G. Aubrey ◽  
Douglas L. Inman ◽  
Charles E. Nordstrom
Keyword(s):  
Sediment Transport ◽  
Incident Wave ◽  
Wave Energy ◽  
Energy Conditions ◽  
Beach Profile ◽  
High Wave ◽  
Wave Characteristics ◽  
Spectral Estimates ◽  
High Wave Energy ◽  
Incident Waves

Beach profiles have been measured at Torrey Pines Beach, California for four years and correlated with tides and accurate spectral estimates of the incident wave field. Characteristic equilibrium beach profiles persist for time spans of up to at least two weeks in response to periods of uniform incident waves. These changes in the beach profiles are primarily due to on-offshore sediment transport which can be related to variations in wave characteristics and tidal phase. The most rapid readjustment of the beach profile occurs during high wave energy conditions coincident with spring tides. Alternatively, the highest berm building is associated with moderate to low waves that coincide with spring tides.

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.

Research on Jiepai Riverbed Evolution Law and its Evolution Trend Forecast in Middle Yangtze River

2014 ◽  
Vol 926-930 ◽  
pp. 4292-4297
Author(s):  
Cheng Tao Huang
Keyword(s):  
Sediment Transport ◽  
Yangtze River ◽  
Mathematic Model ◽  
Beach Erosion ◽  
Main Stream ◽  
Reservoir Impoundment ◽  
Close Relationship ◽  
Bed Evolution ◽  
The Right ◽  
Evolution Trend

After Three Gorges reservoir impoundment, sediment transport and bed evolution characteristic had changed in the lower Yangtze River. Based on the observational data, sediment transport and bed evolution characteristic of Jiepai reach had been analyzed. The results showed that Jiepai reach evolution had a close relationship with income flow and sediment conditions. In recent years, the income flow and sediment conditions were propitious to the development of left slot of heart beach. It also had accelerated the low beach erosion in transition section and siltation in Xindijia. A 2-D mathematic model and river physical model had been used to forecast the river evolution trend. The results showed that the staggered beach would still not stay steady with the reservoir impoundment. The periodic time of evolution could become longer. Xiru bank beach in right bank of upper Jiepai reach would deposit and move downwards. The main stream discharge would centralize and increase. The left channel of heart reach would be eroded and the right one would dwindle gradually by the squeezing of the heart reach. The right branch channel, as the main navigation channel, would deposit and become shallow. The transition reach would move downwards at outlet of left channel. The riffle would present a staggered shape and left branch channel would dwindle gradually. The waterway transportation condition would get worse.

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