Hydrodynamics and Morphodynamics Performance Assessment of Three Coastal Protection Structures

Coastal areas accommodate a great part of large metropolises as they support a great amount of economic and leisure activities. The attraction of people to coastal zones is contributing to an intense and continuous urbanization of these areas, while the ecosystems are threatened by the increase of natural extreme weather events (e.g., intensity and duration of storms, floods), which interfere with local wave climate and changes in morphological beach characteristics. Protection of coastal zones predisposed to coastline recession, due to the action of high tides, high sediment transport deficit, and high wave energy, may involve various coastal structures to reduce or at least to mitigate coastal erosion problems. Many of the current coastal protections (notably groins, seawalls, and emerged breakwaters) were built with a single purpose, which was to protect at all costs without environmental or economic concerns, especially maintenance costs, or the negative consequences that such structures could cause up to considerable distances along the coast. The current concept of integrated coastal zone management presupposes studies involving other types of concerns and more actors in the decision-making process for the implementation of coastal works. In this context, multifunctional structures emerge and are increasingly frequent, such as the so-called multifunctional artificial reefs (MFARs), with the aim of improving leisure, fishing, diving, and other sporting activities, in addition to coastal protection. MFARs are in fact one of the latest concepts for coastal protection. Behind the search for more efficient and sustainable strategies to deal with coastal retreat, this study focused on a comparison between the performance of two traditional coastal protection solutions (submerged detached breakwater and emerged detached breakwater) and an MFAR on a particular coastal stretch. In order to analyse the hydro- (wave height and wave energy dissipation) and morphodynamics (sediment accumulation and erosion areas, and bed level) of the structures and beach interactions, two numerical models were used: SWAN (Simulation WAves Nearshore) for hydrodynamics and XBeach for hydrodynamics and morphodynamics. In addition, a comparison between SWAN and XBeach hydrodynamic results was also performed. From the simulations conducted by SWAN and XBeach, it can be concluded that amongst all structures, the emerged detached breakwater was the most efficient in reducing significant wave heights at a larger scale due to the fact that it constituted a higher obstacle to the incoming waves, and that, regarding both submerged structures (detached breakwater and the MFAR), the MFAR presented a more substantial shadow zone. Regarding morphodynamics, the obtained results presented favourable tendencies to sediment accretion near the shoreline, as well as at the inward areas for the three structures, especially for the emerged detached breakwater and for the MFAR in both wave directions. However, for the west wave direction, along the shoreline, substantial erosion was observed for both structures with more noticeable values for the emerged detached breakwater. For all the northwest wave direction scenarios, no noticeable erosion areas were visible along the shoreline. Overall, considering the balance of erosion and accretion rates, it can be concluded that for both wave predominance, the submerged detached breakwater and the MFAR presented better solutions regarding morphodynamics. The MFAR storm wave condition performed in XBeach indicated substantial erosion areas located around the structure, which added substantial changes in the bed level.

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Joint Modelling of Wave Energy Flux and Wave Direction

Processes ◽

10.3390/pr9030460 ◽

2021 ◽

Vol 9 (3) ◽

pp. 460

Author(s):

Takvor H. Soukissian ◽

Flora E. Karathanasi

Keyword(s):

Energy Flux ◽

Wave Energy ◽

Goodness Of Fit ◽

North Atlantic Ocean ◽

Wave Climate ◽

Western Mediterranean ◽

Wave Direction ◽

Bivariate Model ◽

The North ◽

Wave Energy Flux

In the context of wave resource assessment, the description of wave climate is usually confined to significant wave height and energy period. However, the accurate joint description of both linear and directional wave energy characteristics is essential for the proper and detailed optimization of wave energy converters. In this work, the joint probabilistic description of wave energy flux and wave direction is performed and evaluated. Parametric univariate models are implemented for the description of wave energy flux and wave direction. For wave energy flux, conventional, and mixture distributions are examined while for wave direction proven and efficient finite mixtures of von Mises distributions are used. The bivariate modelling is based on the implementation of the Johnson–Wehrly model. The examined models are applied on long-term measured wave data at three offshore locations in Greece and hindcast numerical wave model data at three locations in the western Mediterranean, the North Sea, and the North Atlantic Ocean. A global criterion that combines five individual goodness-of-fit criteria into a single expression is used to evaluate the performance of bivariate models. From the optimum bivariate model, the expected wave energy flux as function of wave direction and the distribution of wave energy flux for the mean and most probable wave directions are also obtained.

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Wave Energy Assessments in the Coastal Environment of Portugal Continental

Volume 6: Nick Newman Symposium on Marine Hydrodynamics; Yoshida and Maeda Special Symposium on Ocean Space Utilization; Special Symposium on Offshore Renewable Energy ◽

10.1115/omae2008-57820 ◽

2008 ◽

Cited By ~ 3

Author(s):

Eugen Rusu ◽

C. Guedes Soares

Keyword(s):

Wave Energy ◽

Numerical Models ◽

Specific Area ◽

Wave Climate ◽

Coastal Environment ◽

Wave Power ◽

Relevant Parameter ◽

Density Spectrum ◽

Energy Devices ◽

Power Resources

The potential for wave energy extraction can be obtained from the analysis of the wave climate which can be determined with numerical models. The wave energy devices can be deployed in offshore, nearshore and shoreline. From this reason, it is important to be able to assess properly the spatial distribution of the wave energy in various locations from the offshore to the coastline in a specific area. The methodology proposed here considers a SWAN based wave model system focusing in the Portuguese continental coastal environment from deep water towards the nearshore. An analysis of the average and high energetic conditions was first performed for a ten-year period, between 1994 and 2003, considering the most relevant in situ measurements available in the Portuguese nearshore. In this way both the average and high energetic conditions corresponding to the Portuguese continental costal environment have been properly defined. For the most relevant average wave conditions, SWAN simulations were performed in some medium resolution areas covering the northern and central parts of Portugal continental, which are traditionally considered richer in wave power resources. The present work allows the identification of some locations in the continental coastal environment of Portugal with greater potential from the point of view of wave power resources. An important observation is related to the fact that the wave power depends on the product between the energy density spectrum and the group velocity of waves. This means that, although the significant wave height is a relevant parameter when assessing the wave power in a specific site, a location having in general higher wave heights is not necessarily also the richest in wave power.

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The Importance of Coastal Observations to Activities of the U.S. Army Corps of Engineers

Marine Technology Society Journal ◽

10.4031/mtsj.44.6.11 ◽

2010 ◽

Vol 44 (6) ◽

pp. 42-53

Author(s):

William Birkemeier ◽

Linda Lillycrop ◽

Robert Jensen ◽

Charley Chesnutt

Keyword(s):

Disaster Preparedness ◽

Numerical Models ◽

Wave Climate ◽

Water Levels ◽

Coastal Protection ◽

Army Corps ◽

Army Corps Of Engineers ◽

Corps Of Engineers ◽

Coastal Mapping ◽

The U.S

AbstractThe U.S. Army Corps of Engineers (Corps) is a project-oriented agency with multiple national missions under its Civil Works program including navigation, hydropower, flood risk management, ecosystem restoration, water supply, regulatory authority for wetlands and U.S. waters, recreation, and disaster preparedness and response. The Corps ocean and coastal activities revolve around the design, construction, and maintenance of specific projects such as channel dredging, coastal protection, beach nourishment, and harbor construction, all requiring research, modeling, and observations. Several Corps activities contribute ocean observations to the Integrated Ocean Observing System (IOOS®) and have requirements for existing or planned IOOS observations. Collected observations include long-term coastal wave climate, water levels, and coastal mapping data information. These provide project-specific and regional data that are used to develop and verify numerical models which are extensively used in project design and to evaluate project costs, benefits, and associated risk. An overview of the Corps coastal activities, data collection, and modeling programs is provided along with information regarding how IOOS coastal and ocean data are being used by the Corps.

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Air Turbine and Primary Converter Matching in Spar-Buoy Oscillating Water Column Wave Energy Device

Volume 8: Ocean Renewable Energy ◽

10.1115/omae2013-11213 ◽

2013 ◽

Cited By ~ 3

Author(s):

J. C. C. Henriques ◽

A. F. O. Falcão ◽

R. P. F. Gomes ◽

L. M. C. Gato

Keyword(s):

Water Column ◽

Wave Energy ◽

Rotational Speed ◽

Time Domain Analysis ◽

Wave Climate ◽

Numerical Code ◽

Oscillating Water Column ◽

Wave Direction ◽

Power Performance ◽

Air Turbine

The oscillating water column (OWC) equipped with an air turbine is possibly the most reliable type of wave energy converter. The OWC spar-buoy is a simple concept for a floating OWC. It is an axisymmetric device (and so insensitive to wave direction) consisting basically of a (relatively long) submerged vertical tail tube open at both ends and fixed to a floater that moves essentially in heave. The air flow displaced by the motion of the OWC inner free-surface, relative to the buoy, drives an air turbine. The choice of air turbine type and size, the regulation of the turbine rotational speed and the rated power of the electrical equipment strongly affect the power performance of the device and also the equipment’s capital cost. Here, numerical procedures and results are presented for the power output from turbines of different sizes equipping a given OWC spar-buoy in a given offshore wave climate, the rotational speed being optimized for each of the sea states that, together with their frequency of occurrence, characterize the wave climate. The new biradial self-rectifying air turbine was chosen as appropriate to the relatively large amplitude of the pressure oscillations in the OWC air chamber. Since the turbine is strongly non-linear and a fully-nonlinear model of air compressibility was adopted, a time domain analysis was required. The boundary-element numerical code WAMIT was used to obtain the hydrodynamic coefficients of the buoy and OWC, whereas the non-dimensional performance curves of the turbine were obtained from model testing.

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Preliminary Modeling and Analysis of a Horizontal Pressure Differential Wave Energy Converter

Volume 7: Ocean Space Utilization; Ocean Renewable Energy ◽

10.1115/omae2012-83169 ◽

2012 ◽

Author(s):

J. Cameron McNatt ◽

H. Tuba Özkan-Haller ◽

Michael Morrow ◽

Michael Delos-Reyes

Keyword(s):

Transfer Function ◽

Wave Energy ◽

Wave Spectrum ◽

Wave Climate ◽

Wave Condition ◽

Modeling And Analysis ◽

Wave Energy Converters ◽

Wide Range ◽

Horizontal Pressure ◽

Spatially Varying

Wave energy converters (WECs) have been proposed that take advantage of spatially varying pressure differentials (PDs) in a wave field to drive a fluid flow. In order to accurately assess the pressure forcing on PD devices, physics-based relationships between major device parameters and device performance need to be determined. Herein, a transfer function is developed that relates horizontally oriented PD device configurations and wave conditions to the amount of pressure forcing available to the device. Investigation of the transfer function confirms intuitive expectation, but also yields surprising results. The transfer function can be applied to a wave spectrum to create a pressure resource spectrum. By manipulating the device length and orientation, an optimal configuration can be found that maximizes the total harnessable pressure resource for a given wave condition or a wave climate. Optimal device lengths for directional seas are longer than those for non-directional seas, and a wide range of suboptimal configurations yields a reasonable pressure resource. The pressure resource transfer function is a fundamental tool for understanding how horizontal PD WECs work and designing an optimal device.

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Modeling Sea Ice Effects for Wave Energy Resource Assessments

Energies ◽

10.3390/en14123482 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3482

Author(s):

Ruth Branch ◽

Gabriel García-Medina ◽

Zhaoqing Yang ◽

Taiping Wang ◽

Fadia Ticona Rollano ◽

...

Keyword(s):

Sea Ice ◽

Wave Height ◽

Wave Energy ◽

Numerical Models ◽

Energy Resource ◽

Wave Climate ◽

Wave Power ◽

Wave Energy Converters ◽

Wave Models ◽

Mean Square Errors

Wave-generated power has potential as a valuable coastal resource, but the wave climate needs to be mapped for feasibility before wave energy converters are installed. Numerical models are used for wave resource assessments to quantify the amount of available power and its seasonality. Alaska is the U.S. state with the longest coastline and has extensive wave resources, but it is affected by seasonal sea ice that dampens the wave energy and the full extent of this dampening is unknown. To accurately characterize the wave resource in regions that experience seasonal sea ice, coastal wave models must account for these effects. The aim of this study is to determine how the dampening effects of sea ice change wave energy resource assessments in the nearshore. Here, we show that by combining high-resolution sea ice imagery with a sea ice/wave dampening parameterization in an unstructured grid, the Simulating Waves Nearshore (SWAN) model improves wave height predictions and demonstrates the extent to which wave power decreases when sea ice is present. The sea ice parametrization decreases the bias and root mean square errors of wave height comparisons with two wave buoys and predicts a decrease in the wave power of up to 100 kW/m in areas around Prince William Sound, Alaska. The magnitude of the improvement of the model/buoy comparison depends on the coefficients used to parameterize the wave–ice interaction.

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MORPHOLOGY AND DYNAMICS OF CRESCENTIC BAR SYSTEMS

Coastal Engineering Proceedings ◽

10.9753/icce.v18.59 ◽

1982 ◽

Vol 1 (18) ◽

pp. 59

Author(s):

V. Goldsmith ◽

D. Bowman ◽

K. Kiley ◽

B. Burdick ◽

Y. Mart ◽

...

Keyword(s):

Wave Height ◽

Wave Energy ◽

Field Studies ◽

Wave Climate ◽

Phase Correlation ◽

Mature Stage ◽

Wave Direction ◽

Significant Wave ◽

Wave Measurements ◽

Wave Heights

Aerial photograph and field studies in the southeastern Mediterranean, involving bathymetric mapping, and concurrent and antecedent wave measurements, have been used to delineate the sequential development of crescentic bars and associated dynamics. The bar sequence includes multiple parallel or wavy bars, ridge and runnels, oblique/transverse bars, single crescentic and double crescentic bars, and occurs during a calming down of wave activity from 2.5 to 0.5 m waves. The concomitant wave data, including wave directions, energy spectrum, significant wave height, and length of the calm period, showed strong correlation with the bar stages. An increase in total bar occurrence during summer is related to a major wave energy decrease in the spring, when significant wave heights (H ) < 1 m sharply increase to 70-85% in April-May. Inner single crescentic and initial double-crescentic bars are largely restricted to the calmest wave months of May/April to October/November, which reflects their sensitivity to wave energy. The aseasonal occurrence is best shown by the mature double crescentic type, which apparently is the final stage in the crescentic bar development sequence. Two bar developmental sequences were delineated: one shore-normal and the other initially oblique, but gradually rotating to shore-normal in the mature stage. Out of phase relationships between inner and outer bar systems resulted from the lag in response of the outer bars behind changes in wave direction. Among the inner crescentic bars and shore rhythms, phase-correlation was the rule. Crescentic bars are well developed on this coast because of the dissipative conditions and the distinct wave climate. High waves in the winter remove the existing bars, and extended calms allow the full development of the crescentic bar sequence. Similar bar types occur on different coasts in different sequences and in different proportions of time. Thus, it is suggested that these differences are attributable to global differences in the occurrences of threshold wave height conditions .

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WAVE ENERGY CONVERSION USING A BLOW-JET SYSTEM

Coastal Engineering Proceedings ◽

10.9753/icce.v32.structures.62 ◽

2011 ◽

Vol 1 (32) ◽

pp. 62 ◽

Cited By ~ 1

Author(s):

Edgar Mendoza-Baldwin ◽

Rodolfo Silva-Casarín ◽

Rafael Sánchez-Dirzo ◽

Xavier Chávez-Cárdenas

Keyword(s):

Potential Energy ◽

Transmission Coefficient ◽

Experimental Work ◽

Wave Energy ◽

Wave Climate ◽

Coastal Protection ◽

Wave Energy Conversion ◽

Wave Energy Converters ◽

Geometric Designs ◽

Real Chance

This paper presents the results of exhaustive experimental work focused on evaluating the efficiency of two devices as wave energy converters and as coastal protection alternatives. The first device is a wave amplifier that by means of overtopping stores water in a reservoir where potential energy can be used to produce power. The second device, the Blow-Jet, is a novel proposal that gathers together the operation of a tapchan and a blowhole to generate an intermittent jet that can easily feed a turbine. Results show that for both devices there is a strong dependency on the wave climate but that there is a possibility of optimizing geometric designs. Transmission coefficient values obtained for the Blow-Jet point to a real chance for its use as a multi-purpose coastal structure.

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The Effect of a Wave Energy Farm Protecting an Aquaculture Installation

Energies ◽

10.3390/en11082109 ◽

2018 ◽

Vol 11 (8) ◽

pp. 2109 ◽

Cited By ~ 3

Author(s):

Dina Silva ◽

Eugen Rusu ◽

C. Guedes Soares

Keyword(s):

Wave Energy ◽

Positive Impact ◽

Wave Climate ◽

Coastal Protection ◽

Wave Energy Converters ◽

The North ◽

Wave Conditions ◽

Offshore Aquaculture ◽

Wave Farm ◽

The Impact

This paper assesses the impact of a farm of wave energy converters on a nearby offshore aquaculture installation and on the nearshore dynamics. The coastal area targeted is Aguçadoura, located in the north of Portugal, where the world’s first wave farm operated in 2008. The study is focused mainly on the evaluation of the sheltering effect provided by the wave farm to the aquaculture cages. Furthermore, the possible impact on the coastal wave climate of such an energy park is also evaluated. These objectives are accomplished by performing simulations, corresponding to the wave conditions, which are more often encountered in that coastal environment. The SWAN model (Simulating WAves Nearshore) was adopted for this. Various transmission scenarios are considered to account for the impact of different types of wave converter farms on the downwave conditions. The results show that such a wave energy park might have a clear positive impact on the wave conditions fish farm installed downwave and it might also have a beneficial influence on shoreline dynamics from the perspective of coastal protection.

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Wave-to-Wire Model Development and Validation for Two OWC Type Wave Energy Converters

Energies ◽

10.3390/en12203977 ◽

2019 ◽

Vol 12 (20) ◽

pp. 3977 ◽

Cited By ~ 5

Author(s):

Pierre Benreguig ◽

James Kelly ◽

Vikram Pakrashi ◽

Jimmy Murphy

Keyword(s):

Wave Energy ◽

Numerical Models ◽

Power Conversion ◽

Electrical Power ◽

Model Development ◽

Wave Structure ◽

Experimental Tests ◽

Wave Climate ◽

Type Wave ◽

Conversion Stage

The Tupperwave device is a closed-circuit oscillating water column (OWC) wave energy converter that uses non-return valves and two large fixed-volume accumulator chambers to create a smooth unidirectional air flow, harnessed by a unidirectional turbine. In this paper, the relevance of the Tupperwave concept against the conventional OWC concept, that uses a self-rectifying turbine, is investigated. For this purpose, wave-to-wire numerical models of the Tupperwave device and a corresponding conventional OWC device are developed and validated against experimental tests. Both devices have the same floating spar buoy structure and a similar turbine technology. The models include wave-structure hydrodynamic interaction, air turbines and generators, along with their control laws in order to encompass all power conversion stages from wave to electrical power. Hardware-in-the-loop is used to physically emulate the last power conversion stage from mechanic to electrical power and hence validate the control law and the generator numerical model. The dimensioning methodology for turbines and generators for power optimisation is explained. Eventually, the validated wave-to-wire numerical models of the conventional OWC and the Tupperwave device are used to assess and compare the performances of these two OWC type wave energy device concepts in the same wave climate. The benefits of pneumatic power smoothing by the Tupperwave device are discussed and the required efficiency of the non-return valves is investigated.

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