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This paper aims at evaluating the wave overtopping discharge over the pavement of &ldquo, Piazza S. Marco&rdquo, (Venice) in order to select the best option to mitigate the risk of flooding of the Piazza and to protect the monuments and historic buildings, e.g., the &ldquo, Basilica S. Marco&rdquo, In fact, the MO.S.E. (MOdulo Sperimentale Elettromeccanico) system is designed to keep the water level below a certain value, for the safety of the lagoon, but it does not guarantee the defence of the Piazza, where flooding is still possible, being its pavement locally much lower than the maximum expected water level. To completely defend the Piazza, specific additional works are planned to prevent the back-flow through the natural drainage system (now the primary pathway) or by filtration or by overtopping. This paper investigates on the overtopping mechanism, under conditions compatible with a fully operational MO.S.E. system, through 2-D experiments. The pavement of the Piazza is gently sloping towards the masonry quay which, in some parts is formed by 5 descending steps, and in some other parts, is just a vertical wall. Close to the &ldquo, Marciana&rdquo, Library, a critical part is present, with a slightly lower crest freeboard. In total, three cross-sections were examined in the 36 m long wave flume of the Padova University. The test programme includes 10 irregular wave attacks and three different water levels. The test results differ considerably from the results of the available formulas, since the investigated cross-sections by far exceed their range of applicability. The presence of the steps affects only the reflection coefficient rather than the overtopping discharges. In general, if the waves incident to the Piazza are higher than 40 cm, which is a possible scenario, some other adaptation works must be considered, such as the pavement rise, temporary barriers or the reduction of the waves impacting the quay through, for instance, floating breakwaters.

This note presents the Seabreath wave energy converter, basically a multi-chamber floating oscillating water column device, and the lumped model used to size its chambers, the ducts and the turbine. The model is based on extensive testing carried out in the wave flume of the University of Padova using fixed and floating models with a dummy power take off and indirect measurement of the produced power. A map with the available energy in the Mediterranean Sea is also proposed, showing possible ideal application sites. The Seabreath is finally dimensioned for a quarter scale test application in the Adriatic Sea, with a 3 kW turbine, and a capacity factor of 40%.

This paper discusses the key aspects of the recent Coastal Plan of the Veneto Region (IT). Its aim is to propose a single mitigation strategy for coastal erosion that is valid for the whole Veneto Region, and possibly elsewhere, as well as a method to assign a priority level to any action. The suggested mitigation action against erosion depends on urbanization level, beach width, as well as cross-shore and long-shore sediment transport. The criterion used to give a priority level to mitigation actions is based on a vulnerability index that takes into account erosive tendency, existing coastal flooding hazards, coast value, environmental relevance, tourist pressure, urbanization level, the presence of production activities, and cultural heritage. A sample case featuring the littoral of Rosolina is also provided and includes a site description, the sediment budget, critical issues and possible mitigation measures.

The general aim of this paper is to examine the effect of floating breakwater layouts on wave transmission, loads along moorings and connectors, under oblique waves. The specific contribution of this work is to provide novel and accurate experimental results for a configuration that is widely adopted in existing prototypes. Tests were carried out in the wave basin (3.8 m×20.6 m×0.8 m) of the Maritime Laboratory of the University of Padova, Italy. Two layouts, characterised by different degrees of complexity (I- and J-shaped), and three obliquities (0∘,30∘,60∘) were examined. With increased wave obliquity, the floating breakwater becomes more efficient thanks to the decrease of wave transmission and of the forces along moorings and connectors. Under perpendicular waves, with increasing layout complexity, no significant effect on wave transmission is observed, whereas mooring and intermodule connector forces significantly change, particularly in the case of frequent overtopping.

The aim of this paper is to define a simple and useful formula to predict wave transmission for a common type of floating breakwater (FB), supplied with two lateral vertical plates protruding downward, named π-type FB. Eight different models, with mass varying from 16 to 76 kg, anchored with chains, have been tested in the wave flume of the Maritime Laboratory of Padova University, under irregular wave conditions. Water elevation in front and behind the structure has been measured with two arrays of four wave gauges. Our starting point for the prediction of wave transmission was the classical relationship established by Macagno in 1954. His relationship was derived for a box-type fixed breakwater assuming irrotational flow. Consequently, he significantly underestimated transmission for short waves and large drafts. This paper proposes an empirical modification of his relationship to properly fit the experimental results and a standardized plotting system of the transmission coefficient, based on a...

The design of a mooring system of a Wave Energy Converter is a challenging process that points out several unsolved technical problems, mostly related to the highly non-linear hydrodynamic phenomena occurring when high waves (e.g. 8 m high with 200 m wavelength) propagate in relatively shallow waters (e.g. 20 m). The aim of this note is to point out the relevance of the non-linear response of a WEC anchored in relatively shallow waters (shallow in the “non-linear” sense) in terms of loads applied to the mooring lines. Further, the effects of this cyclic load on the anchors is investigated. Note that to some extent it is like checking the importance of geotechnical and coastal engineers in the design process of the WEC structure and its mooring system (typically carried out by naval architects). The whole mooring design process is first outlined and then it is schematically applied to a specific case, namely a promising Italian device named SeaBreath (www.seabreath.it), in view of a possible deployment in the Adriatic Sea. The main concern of mooring designers is related to resonance effects induced by the second order drift. Therefore specific tests have been carried out in the 36 m long x 1.0 m wide x 1.3 m high wave flume of Padova University. Tests focused on the forces on the mooring lines induced by the sum of two regular waves of similar frequency. The mooring design is still far from complete: the physical model proved the relevance of the aforementioned effects but a numerical investigation (not yet performed) is required to draw final conclusions.

This note presents further experimental evidence on the effect of the layout on the mooring forces of floating breakwaters under irregular waves. The latest results, here summarized, have been obtained by means of physical model tests carried out on an L-shaped layout and are compared to data previously published by the authors. The experimental facility is located at the University of Padova, Italy. Results are given in non-dimensional form and concern the transmission phenomenon and the loads on mooring and tie rods interconnecting adjacent modules. It is confirmed that under more complex layouts, the wave transmission increases, due to smaller dissipation, maximum mooring forces decrease and link forces largely increase.

Aim of this contribution is to investigate the relevance of the layout on the performance of floating breakwater schemes under oblique waves. An experimental investigation was carried out in the wave basin of the Maritime Laboratory of Padua University, Italy. The facility dimensions are 3.8m x 20.6m x 0.8m. Several regular and irregular longcrested waves were generated and two different layouts (I- and J-shaped) and three obliquities (0°, 30°, 60°) were tested. With increasing wave obliquity, wave transmission decreases, mooring forces due to snapping decrease and link forces slightly increase. The J-shaped configuration determines basically the same effects with regards to both transmission and loads. The maxima of link forces are not much greater than the average loads and this is relevant for fatigue and reliability considerations.

Aim of this contribution is to examine the load on the mooring and on the tie rods of a set of interconnected floating bodies under extreme waves, with particular attention to the layout obliquity. Tests carried out at the IMAGE department of Padova University are briefly presented. It is doubtful how to scale the laboratory tests in the presence of impulsive loads on semi-taught moorings. In order to find proper scaling laws, a numerical model is presented where the chain and the floating body are studied as a lumped mass system. Results, compared to available laboratory tests are encouraging and it appears that the main processes in presence of impulses are correctly represented by the model. Model calibration will be carried out shortly, on the basis of specific ongoing tests on floating Wave Energy Converters.Copyright © 2009 by ASME

The aim of this work is to assess, by means of available experimental results and numerical simulations, the possible extension of the range of application of the formula proposed by Ruol et al. (J. Wat. Port, Coast. Ocean Eng., 1, 2013), giving wave transmission for chain-moored -type floating breakwaters. The formula is here applied out of the range used for its calibration and even to other types of FBs. The error between predicted and measured values is described and discussed with reference to the main geometrical variables. It appears that the formula performs fairly well for the box-type FB, but not in cases characterized by very different mooring stiffness compared to the one used for calibration. For instance in case of fixed or tethered FBs, the formula significantly overestimates the wave transmission.

Aim of this note is to analyse the possible application of a Wave Energy Converter (WEC) as a combined tool to protect the coast and harvest energy. Physical model tests are used to evaluate wave transmission past a near-shore floating WEC of the wave activated body type, named DEXA. Efficiency and transmission characteristics are approximated to functions of wave height, period and obliquity. Their order of magnitude are 20% and 80%, respectively. It is imagined that an array of DEXA is deployed in front of Marina di Ravenna beach (IT), a highly touristic site of the Adriatic Coast. Based on the CERC formula, long-shore sediment transport is evaluated in presence and in absence of this array of DEXAs. The sediment transport in this site is quite large and frequently changes directions during the year. The larger North directed contribution and the more persistent South directed one are similar in magnitude and almost compensate each other, with the latter only slightly prevailing. It is shown that the DEXA could be designed so that the effect on sediment transport becomes quite significant and the direction of the net transport can be reversed.

This note presents wave flume experiments, carried out at Aalborg University, measuring the horizontal sliding distance of a vertical breakwater in 1:40 scale. Horizontal and uplift wave induced pressures were accurately measured simultaneously with the caisson movements. Caissons of different weight and same geometries are tested under regular and irregular waves. It is found that, under breaking conditions, the expected inaccuracy of the prediction of the force, inherent on the variability of the breaking process, induce unacceptable errors in the prediction of the sliding. This observation endorses other previous experimental results. Conversely, when the actual measured input force is used as input, the analytical Shimosako formula fit quite well the experimental sliding distance.

In view of a potential design of a 2 kW small scale prototype of a wave energy converter named Seabreath, the dimensioning of the power take off, generator and relative electrical equipment is under investigation. This note presents an innovative research focusing on a holistic description of the behaviour of this device. Within a Marinet application (FP7 Research Infrastructure Action) named “Multi-chamber oscillating water column device for harvesting Ocean Renewable Energy” (MORE), electrical experiments have been carried out in the “hardware in the loop” test bench in Tecnalia laboratory, Bilbao, in order to test different control strategies. For these experiments, the Electrical and hydrodynamic response need to be fully coupled. The note describes how the available hydrodynamic model of the Seabreath has been modified to be coupled to the new electric experiments. Since the electrical tests are being used to calibrate an electrical numerical model, the procedure depicts an innovative and complete type of wave-2-wire model of a wave energy converter.