Diego Vicinanza

Wave loadings acting on Overtopping Breakwater for Energy Conversion

ABSTRACT Vicinanza, D., Nørgaard, J.H., Contestabile, P. and Andersen, T.L., 2013. Wave loadings acting on Overtopping BReakwater for Energy Conversion. Any kind of Wave Energy Converter (WEC) requires information on reliability of technology and on time required for the return of the investment (reasonable payback). The structural response is one of the most important parameters to take in to account for a consistent assessment on innovative devices. This paper presents results on wave loading acting on an hybrid WEC named Overtopping BReakwater for Energy Conversion (OBREC). The new design is based on the concept of an integration between a traditional rubble mound breakwater and a front reservoir designed to store the wave overtopping from the incoming wave to produce electricity. 2D hydraulic model tests were carried out at the Department of Civil Engineering, Aalborg University (Denmark). The analyses of hydraulic model tests have identified the main shapes assumed by wave surfaces at the breakwater and respective spatial and temporal pressure distributions. Load measurements were compared with the most used prediction method for traditional breakwaters, available in the Coastal Engineering Manual (U.S. Army Corps of Engineers, 2002). These results suggest to use the experimental data as design loadings since the design criteria for the innovative OBREC are under development.

Large-scale experiments on the behaviour of low crested and submerged breakwaters in presence of broken waves

Functional design of low crested breakwaters requires an accurate prediction of wave transmission and set up in the protected areas. Nevertheless, commonly used formulae do not appear to be reliable enough, especially for structures located in shallow waters. The paper describes results from large-scale model tests conducted on rubble mound breakwaters exposed to breaking waves. Tests were carried out at the “Grosser WellenKanal” of Hannover, Germany. The model dimension, near to prototype, allowed minimizing scale effects connected to wave breaking. Existing formulas on wave transmission have been verified and influence of crest width and breaker index have been highlighted. Moreover the wave set-up behind the structure has been analysed showing the importance of momentum release of breaking waves for submerged breakwaters and of the mass balance for low crested ones. 8.

Potential wave energy production by different wave energy converters around Sicily

The performance of several Wave Energy Converter devices is evaluated at three sites located on the west side of Sicily. To select the most energetic site, the average potential wave energy along the coasts of Sicily is evaluated by adopting a third-generation spectral wave propagation model using as boundary conditions the European Centre for Medium-Range Weather Forecasts operational archive wave and wind data. The most energetic sites are on the western side of Sicily. In the three hotspots identified, the mean energy flux is within the range of 5.33–7.52 kW/m. The analysis shows that all considered devices have a low capacity factor in their original configurations (2.19%–5.12%). The main causes of the poor results in terms of energy production are related to the fact that such devices are optimized for high-energy waves. A resizing of the devices on the basis of the local wave climate showed that a capacity factor that exceeds 30% could be obtained.

Marine Renewable Energies: Perspectives and Implications for Marine Ecosystems

Countries with coastlines may have valuable renewable energy resources in the form of tides, currents, waves, and offshore wind. The potential to gather energy from the sea has recently gained interest in several nations [1–3], so Marine Renewable Energy Installations (hereinafter MREIs) will likely become very diffuse in the near future and determine a further transformation of our coastal seas.

Large-scale morphodynamic experiments on a beach drainage system

This research describes a unique set of experiments undertaken at the Large Wave Channel (Hannover) aimed to study the morphodynamic behaviour of a beach face containing a buried drainage system. The advantage of using a large wave flume is that scale effects that affected previous laboratory experiments are minimized. This compares the response of the undrained beach under controlled wave forcing with the response of the drained one with the same wave action. Low, medium and high levels of wave energy were used for the experiments, with significant wave heights of 0.39–0.83 m and wave steepnesses between 0.004 and 0.013. Any positive effect of the drains on the beach face was confined by the position of the cone of depression in the aquifer surface. The best performance of the system was observed with two drains operating at the same time under low to moderate wave energy.

Full-scale experiments on a beach drainage system: hydrodynamic effects inside beach

An extensive full-scale laboratory investigation on a two-dimensional physical model of a beach drainage system (BDS) was performed at “Grosser Wellen-Kanal” of Hannover, Germany. This research deals with the hydrodynamic aspects of a beach equipped with a BDS, while the morphodynamic aspects of the study are discussed in a companion paper. Knowledge of both the hydrodynamic and the morphodynamic behaviours of a drained beach allows the definition of the main design criteria. The adopted BDS was constituted by four corrugated pipes. Several drain configurations in static and dynamic conditions were considered, paying attention to water table oscillations, drains and groundwater regime and drainage discharge induced by the system start-up. The main results indicate a rise in the unsaturated beach and the presence of a hydraulic disconnection in the groundwater–drain system. The analyses yield useful hydrodynamic information influencing the general system efficiency.

Performance of a Beach Dewatering System—Chiaiolella Beach, Procida Island, Italy

Abstract Chiaiolella Beach is a 1.5-km-long pocket beach located on Procida Island (Italy). The beach is formed by medium sand generated by erosion of vulcanoclastic rocks that form cliffs around the island and at the backshore of the study site. A beach dewatering system was installed in April 2002 to provide a wider beach for users and to prevent cliff undercutting during storms. It has not been operative since December 2004, as local authorities decided to undertake cliff stabilization measures. Surveys carried out immediately before (October 2001) and 1 year after installation (October 2002) showed negligible volumetric change on the drained beach in Ciraccio (−0.52 m3/m), the NNE sector of Chiaiolella Beach, whereas on the undrained control section there was an accumulation of 1.41 m3/m. Since no long-term monitoring of beach profiles was available at the site previous to installation, to obtain an indication of the nearshore hydrodynamics and morphodynamics in absence of the drain, historical shoreline from high-resolution georeferenced aerial photography and numerical model were used. Overall, no evident positive effects of the dewatering system were confirmed, at least for mild wave energy levels. For higher wave energies, e.g., during a storm that occurred in December 2002, part of the beach (SSW sector, Ciracciello) had consistent volume losses and the dewatering system was not able to compensate them, as at some stage it was even damaged. This study points out the inadequacy of the dewatering system as coastal protection under high wave conditions.

Beach sediment mixing under drained and undrained conditions

ABSTRACT Ciavola, P., Contestabile, P., Aristodemo, F., and Vicinanza, D., 2013. Beach sediment mixing under drained and undrained conditions. The paper describes a set of experiments undertaken at the Grosser Wellen Kanal (GWK) in Hannover on sediment mixing on a beachface exposed to the action of a buried drainage system. Experiments were performed using a set of drains (up to three working simultaneously), located at variable distance from the shoreline. Wave energy during the tests ranged from medium (0.59 m < Hs < 0.61 m) to high (0.76 m < Hs < 0.83 m). Beach profiles were measured at the end of each test. Further validation came from measurements using a grid of rods that were monitored at the same time as the beach profiles were surveyed. While some beach stabilization was observed for low energy conditions, for medium and high energy conditions the benefit of having the drains operative was not so clear. The comparison between beach profiler and rods showed good agreement regarding relative vertical accretion and erosion events. In any case, it was evident that the sedimentary effect on the beachface was confined to a narrow area above the drains. The drained area showed slightly lower values of sediment mixing under drained conditions, but evidently this factor was not important enough to trigger a widespread beach stabilization. Values of sediment mixing averaged across the whole beachface ranged between 2–4 % and 4–6 % of the breaking wave height respectively for high and medium energy wave conditions. Grain size, beach slope and drain configurations used here are fully comparable to field installations present in the literature.

Spatial Distribution of Wave Pressures on Seawave Slot-Cone Generator

acceptance number 166 SPATIAL DISTRIBUTION OF WAVE PRESSURES ON SEAWAVE SLOT- CONE GENERATOR 1 Author: Vicinanza, Diego 2 Author: Margheritini, Lucia 3 Author: Frigaard, Peter Breakwaters Coastal structures Dynamic response Inlets Long waves Overtopping Wave generation

Swash zone response under various wave regimes

The modelling of swash zone (SZ) sediment transport and the resulting morphodynamics have been areas of active research over the last decade. However, many details are still to be understood, whose knowledge will be greatly advanced by the collection of high-quality data under the controlled large-scale laboratory conditions. The research describes tests carried out in the large wave flume of the Maritime Engineering Laboratory at Catalonia University of Technology, to investigate the SZ under the storm conditions. Its main aim was to compare beach-profile responses for monochromatic waves, monochromatic waves plus free long waves, bi-chromatic waves and random waves. Both erosive and accretive conditions were considered. Results discussed here were derived from the analysis of only a part of the whole data set.