Publications

This paper presents a study of run-up/overtopping over a smooth impermeable dike with promenade using 2D and 3D mesh-based and mesh-free numerical models and results from 2D physical modelling for strong energetic incident waves. These waves induce plunging wave breaking and a complex water/air mixture turbulent flow before overtopped the dike, a challenging configuration for numerical models. The analysis is structured in two phases: (i) evaluates the results of 2D numerical and physical models for run-up and overtopping; (ii) compares qualitatively the results of 3D numerical models for overtopping over a dike with promenade between groins located in front of a slope beach. The results indicate that the main differences obtained in run-up and overtopping are due to differences in wave generation and active absorption systems used in physical and numerical models and in turbulent models used by the numerical models. These differences lead to changes on incident wave height and on wave breaking and, consequently, on reflection, run-up and overtopping over the structure. For 3D simulation, even if larger discrepancies were found on overtopping along the dike, mean wave overtopping discharge and water flow height at the crest of the groin head show a similar order of magnitude.

Artificial neural networks (ANN) are extremely powerful analytical, parallel processing elements that can successfully approximate any complex non-linear process, and which form a key piece in Artificial Intelligence models. Its field of application, being very wide, is especially suitable for the field of prediction. In this article, its application for the prediction of the overtopping rate is presented, as part of a strategy for the sustainable optimization of coastal or harbor defense structures and their conversion into Waves Energy Converters (WEC). This would allow, among others benefits, reducing their initial high capital expenditure. For the construction of the predictive model, classical multivariate statistical techniques such as Principal Component Analysis (PCA), or unsupervised clustering methods like Self Organized Maps (SOM), are used, demonstrating that this close alliance is always methodologically beneficial. The specific application carried out, based on the data provided by the CLASH and EurOtop 2018 databases, involves the creation of a useful application to predict overtopping rates in both sloping breakwaters and seawalls, with good results both in terms of prediction error, such as correlation of the estimated variable.

O projeto de investigação e desenvolvimento To-SEAlert financiado pela Fundação para a Ciência e a Tecnologia e envolvendo o LNEC, a FCiências.ID, a NOVA.ID.FCT e o ISEL tem como objetivo o desenvolvimento de um sistema de previsão, alerta, planeamento de emergência e gestão de risco de galgamentos e inundações em zonas costeiras e portuárias, com base no sistema HIDRALERTA. Partindo das características da agitação marítima ao largo e utilizando modelos numéricos para a propagação e deformação da agitação marítima, o sistema HIDRALERTA estima os parâmetros relevantes da agitação marítima para a avaliação do galgamento e da inundação bem como o risco associado a esses eventos. As funcionalidades que se pretendem melhorar no âmbito do projeto To-SEAlert dizem respeito às metodologias de previsão do galgamento e da delimitação da zona inundada, bem como no apoio à resposta a situações de emergência envolvendo fenómenos de galgamento. A implementação e a validação do protótipo do To-SEAlert estão a ser efetuadas para a zona costeira da Costa da Caparica e para o porto da Ericeira. Este artigo apresenta o trabalho desenvolvido até à data na construção e desenvolvimento do protótipo do To-SEAlert para o porto da Ericeira.

Under the scope of the HYDRALAB+ transnational access project, the so-called RODBreak experiment was conducted in the multidirectional wave basin at the Marienwerden facilities of the Leibniz University Hannover (LUH). A stretch of a rubble-mound breakwater was built in the wave basin with a very gentle slope. Its armour layer was made of Antifer cubes, at the roundhead and adjoining trunk, and of rock, at the rest of the trunk.A set of tests was carried out to extend the range of wave steepness values analysed in wave run-up, vertopping and armour layer stability studies, focusing on oblique extreme wave conditions, with incident wave angles from 40º to 90º.The present study focuses on the analysis of measured wave run-up values obtained in the tests and on their on their variability as well as the influence of the wave obliquity and directional spreading.

Several authors have proposed guidelines on how to consider the effects of oblique waves on the stability of armour layers of rubble-mound breakwaters. Especially for very oblique waves, for which the increase in stability is the largest, limited data are available. Under the scope of the HYDRALAB+ transnational access project

This paper describes a program under the responsibility of LNEC for the systematic observation and monitoring of maritime works that has successfully been applied to a number of maritime structures on the Portuguese mainland coast. The now-called OSOM+ program comprises the following four main components for each structure: i) periodic visual inspections by an experienced technician; ii) periodic aerial inspections with a UAV/ drone; iii) a ANOSOM-WEB database, to store and/or query obtained information on the observation campaigns, as well as to diagnose present, evolution and risk conditions of the structure; iv) a mobile, portable, application, for realtime input and visualization of the database information. OSOM+ has recently been updated with a number of tools and functionalities that are illustrated in this paper with applications to two real case studies: the Portimão harbor breakwaters and Faro-Olhão inlet entrance breakwaters, both located in the south coast of Portugal.

Wave energy is a renewable source with significant amount in relation to the global demand. A good concept of a device applied to extract this type of energy is the onshore oscillating water column wave energy converter (OWC-WEC). This study shows a numerical analysis of the diameter determination of two types of turbines, Wells and Impulse, installed in an onshore OWC device subjected to a hypothetical sea state. Commercial software FLUENT, which is based on RANS-VoF (Reynolds Averaged Navier-Stokes equations and Volume of Fluid technique), is employed. A methodology that imposes air pressure on the chamber, considering the air compressibility effect, is used. The mathematical domain consists of a 10 m deep flume with a 10 m long and 10 m wide OWC chamber at its end (geometry is similar to that of the Pico

Para caracterizar a agitação marítima no Porto de Leixões após o prolongamento do quebra-mar exterior, sob condições de alterações climáticas foi realizado um extenso grupo de ensaios em modelo físico tridimensional de agitação, num tanque do LNEC, à escala 1:80, representando-se toda a bacia portuária e o prolongamento do quebra-mar exterior do Porto de Leixões. Foram realizados ensaios com diferentes condições de agitação incidente para o rumo W e com dois níveis de maré, que correspondem ao nível médio e a preia-mar com uma sobrelevação representativa dos efeitos das alterações climáticas e da sua influência na agitação marítima. Foi medida a agitação em 30 pontos localizados na entrada do porto e no interior da bacia portuária e analisou-se o abrigo da bacia portuária com a ampliação do quebra-mar norte e as diferenças entre o abrigo para os dois níveis de maré ensaiados.As principais conclusões dos ensaios realizados foram que os maiores valores de alturas de onda ocorreram na zona exterior e de entrada do porto, diminuindo para o seu interior. Ao longo do canal de navegação, as alturas de onda vão diminuindo e no interior do porto obtiveram-se valores da altura de onda pequenos. A subida do nível do mar, para as condições ensaiadas, não afeta significativamente a agitação no interior da bacia portuária. No entanto, no exterior e zona de entrada do porto contribui para alterações da agitação que diferem consoante o período de pico e a altura de onda significativa incidente.

The vegetation capacity to protect the coasts from wave action is becoming more important and attractive due to ongoing sea level rise and increasing storminess. In addition, it is a quite environmentally friendly way. Quantifying the vegetation effect in wave propagation will be relevant for coastal management. A non-hydrostatic wave model based on the nonlinear shallow water equations, SWASH, offers opportunities to quantify the wave dissipation effect in vegetation fields. However, limited applications of SWASH addressing this subject can be found in the literature and therefore it is important to enhance the existing knowledge on the model behaviour. In this research, in order to understand the characteristics of the SWASH model further, the model is applied to reproduce the significant wave height (Hs ) evolution over vegetation fields measured in flume experiments and in field campaign. Overall, SWASH performed very well in reproducing the Hs evolution measured both in the laboratory and in the field. In the case of flume data, the statistical scores MBE, RMSE and MRE, showed that the SWASH performance clearly improved when increasing the number of vertical layers assumed in the simulations. In the case of field data, considering a vegetation factor (Vf ) between 0.1 and 0.5, that represents the overall effect of scarcely known numerical vegetation parameters, led to a fairly good SWASH performance in modelling the Hs evolution over vegetation.

Nowadays, renewable energy is a topic widely discussed in scientific community. Specifically wave energy attracts attention because it has a high energy potential distributed throughout the planet. Oscillating Water Column (OWC) wave energy converter is one of the most studied devices that have promising perspectives to be installed commercially. This study aims investigating the influence of chamber sizes and turbine characteristics dimensions of an OWC device located at the southern Brazilian coast is carried out. Numerical simulations for incident waves with period T = 7 s and 10 s and height H = 1.5 m, by using the FLUENT® model, based on the finite volume method (VFM) are carried out. Efficiencies for different chamber sizes and Wells turbine characteristic relations (kt) in each incident wave are determined. The highest efficiencies were obtained by a chamber with 5 x 5 m and kt = 530 Pa.s/m³ in the case of an incident wave with T = 7s (52%), and 30 x 30 m and kt = 15 Pa.s/m³ at T = 10s (65%).

Port terminals downtimes lead to large economic losses and largely affect the port

This paper describes the physical model, experimental setup and tests performed to study the motions and forces of a ship moored to the pier A at the Leixões oil terminal, following the breakwater

HIDRALERTA is a forecast, early warning and risk assessment system for port and coastal areas that uses measurements and estimates of sea-waves and water levels to evaluate overtopping/flooding events. The calculation of the mean overtopping discharge over a maritime structure is performed through artificial neural network-based tools and/or empirical formulae. The system is developed in open source software, mainly using the Python language. This paper presents the application of HIDRALERTA system to reproduce the hurricane Lorenzo conditions and impacts at Lajes das Flores port on October 2nd 2019, the most affected port in Azores. This hurricane was regarded as the strongest storm to hit Azores in 20 years. The system predicted the expected results for the hurricane wave characteristics, as well as overtopping discharge volumes. Further validation still need to be improved with the collaboration of the local authorities and the use of historical data.

Numerical models are useful tools to predict the effects of storms in coastal areas. The objective of this work was to simulate the effects of storms in São Pedro de Moel beach by using XBeach. The nearshore sea state was obtained by propagating offshore conditions using the SWAN model. The XBeach model was divided into two setups to analyse overtopping events and coastal evolution. Sensibility tests, calibration, and validation, using information from different storms, were performed for the different setups. The results from the overtopping simulation were compared against results from an empirical formula. The comparison showed lower values obtained with the empirical formula. The coastal evolution run point out to the necessity of having better field data before and after storms to improve the model setting and accuracy.

The assessment of damage evolution in scale model tests of rubble-mound breakwaters can be achieved by comparing eroded depths and volumes between consecutive surveys. This paper focuses on damage evolution of a model of a rubble-mound breakwater and on the novelty of the non-intrusive survey methodologies such as laser scanning and Time of Flight (ToF) techniques, based on point clouds, enabling the extraction of profiles and the calculation of eroded depths and eroded volumes. The final objective of this work is to evaluate the applicability of the estimation the number of displaced armour units, using a non-dimensional damage parameter based on the calculated eroded volume.The paper will also describe the experiments conducted under the RODBreak, a project sponsored by the HYDRALAB+ Transnational Access Program, in which a stretch of a rubble-mound breakwater was built at the wave-current basin of the Leibniz University Hannover (LUH) to assess the structure behavior. Four scan surveys were conducted using a Faro Focus 3D laser scan, as well as a ToF sensor. Those surveys were carried out before and after two test series, in order to evaluate the eroded volume and profile evolution.

Neste trabalho é efetuada a validação do protótipo To-SEAlert para o porto da Ericeira. Para a validação dos resultados do modelo SWAN foram utilizados os dados de duas boias situadas ao largo da Nazaré e para a validação das previsões do sistema de cálculo do grau de risco foram simuladas as depressões Elsa e Fabien (ocorridas em dezembro de 2019) e que foram responsáveis por fortes danos na cabeça do molhe do porto da Ericeira. Verificou-se uma boa concordância entre os dados das boias e os resultados do modelo SWAN, tendo no entanto o modelo reproduzido melhor a direção média e a altura significativa do que o período de pico. Relativamente aos valores de galgamento, os resultados obtidos na simulação das depressões Elsa e Fabien estiveram em concordância com os valores referidos na literatura como causadores de danos nas estruturas.

This work aims to determine the exploitable wave energy resource at six potential sites, located in the Azores, Madeira and Sines breakwater city harbours. For that purpose, the thirdgeneration wave model SWAN is used to estimate the sea-wave conditions over the last 40 years. Boundary conditions of the sea states and wind fields are provided by the climate reanalysis datasets (ERA5). Using those results as inputs to the SWAN model, the sea-states were propagated shoreward, in order to estimate and analyse the wave climate conditions in the regions of interest. By combining the average energy flux per unit-length of wave front and the probability of occurrence of each sea state, the average exploitable annual energy per unit length of wave crest can be computed. The variability of this energy flux is described, since it is of fundamental importance for the efficiency of the Wave Energy Converters (WEC).

Former investigations on wave run-up and overtopping of (impermeable and permeable) coastal structures aimed at quantifying the influence of oblique waves on mean overtopping discharge, water layer thickness and velocities by developing empirical formulas of a reduction factor for wave obliquity,

In 2017, the RODBreak experiment was conducted. The experiment aimed at characterizing wave run-up, overtopping and damage in rubble-mound breakwaters. The reason for these experiments was the huge impact that climate can have on maritime structures, particularly in rubble mound breakwaters. In fact, the forecast sea level rise associated with more frequent and severe storms will have consequences either on the increase of wave runup, wave overtopping or on damage on existent structures since they were not design for those extreme values. However, for those climate change scenarios, little is known about the actual failure probability of such structures.Within this framework, a stretch of a rubble-mound breakwater was built in a wave basin. Under extreme wave conditions, with different incident wave angles (from 40° to 90°), a total of 49 tests were performed. Each test had different testing parameters, such as significant wave height (Hs), peak period (Tp) and wave direction. Also, for each test, different types of measurements were considered. Incident sea waves were measured with 3 arrays of 6 acoustic wave probes each as well as with isolated acoustic wave probes and 5 Acoustic Doppler Velocimeters (ADV

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