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.

This paper presents a comparison of two URANS models based on the VoF approach, FLUENT (Fluent, 2006) and IH2VOF (Lara et al., 2011), to perform a detaiied analysis of the hydrodynamic phenomena outside and inside an open Oscillating Water Coiumn (OWC) device. This analysis is important to determine the ability of each solver in accurate modelling the complex non-linear phenomena which occur in the wave-fluid-structure interaction, in order to use it in the deveiopment of an innovative integrated tool at prototype scale. Numerical results of free surface elevation, oscillating free surface inside the water chamber, amplification factor and phase lag are analysed and compared with experimental data for several incident wave conditions. For an OWC with a fuliy open chamber, good agreement was achieved between experimental data and numerical results obtained with two modeis with different numerical methodologies.

In order to account for scour problems, protection systems are usually employed around the foundations, i.e. Arklow Bank OWF and Scroby Sands OWF (Whitehouse et al., 2011). Their design is main-ly of semi empiric nature (De Vos et al., 2011) and probabilistic approaches haven

An analytical model is applied to a schematic case of an oscillating water column (OWC), without head loss, to obtain a first estimation of the chamber hydraulic efficiency. The IH2VOF numerical model of wave-structure interations is applied to perform an investigation, useful to complement and verify the analytical approach and analyses the flow characteristics on the OWC, including nonlinear effects. The numerical model was validated against physical model tests on a schematic OWC stucture at the National Laboratory of Civil Engineering, presenting god agreement.A significant difference of amplification factor parameter was observed between lhe analytical results and numerical results and experimental data, which may be attributed to the absence of head loss in the analytical model.

Nesta comunicação, descrevem-se os ensaios em modelo físico realizados com o objetivo de caracterizar o campo de ondas em torno de um navio livre, quando sujeito a condições de agitação incidente regular e irregular. Estes dados são especialmente importantes para a validação de modelos numéricos de caracterização da resposta de navios à ação da agitação incidente. Assim, para cada condição de agitação incidente, efetuaram-se medições da elevação da superfície livre e das componentes da velocidade em diversos pontos em redor do navio. Apresentam-se as seguintes análises dos dados experimentais: análise temporal e espetral (espetro de energia e wavelets) dos valores de elevação da superfície livre e análise temporal da velocidade das partículas, a meio da coluna de água. A análise temporal e espetral de cada série de medições obtida permite a caracterização da agitação nos pontos em redor do navio, em termos de alturas, períodos e velocidade. Avalia-se também a influência do navio nas características da agitação.

This paper aims at presenting two diíferent methodologies to evaluale wave overtopping consequences: the Analytic Hierarchy Process (AHP) and the Analytic Network Process (ANP). The AHP is based on lhe comparison of successive and paired information that was selecled and quantified having in mind its hierarchic prioritization by taking into account lhe estimated relevance of each considered criterion or indicator. The ANP provides a general framework lo deal with decisions without making assumplions about the independence of higher level elements from lower level eiements and about the independence of the elements within a levei. In fact, the ANP uses a network without the need lo specify leveis as in a hierarchy structure iike lhe AHP. Influence is a central concept in the ANP. Applicalion of the AHP and the ANP melhodologies to lhe case study of Praia da Vitória harbour (Azores, Porlugal) is presenied. With the AHP, a consequences level map is obtained.

Wave run-up parameters are key factors in studying coastal flooding. An experiment was performed at LNEC to study wave run-up and overtopping on a breakwater.This work investigates the possibility of measuring wave run-up by using a video-monitoring technique.Water level oscillations were identified on the breakwater slope over time. Wave run-up was marked on each timestack image produced for each test.Run-up events were identified and related to the surf similarity parameter. Properties of wave run-up derived from video imagery were analysed and compared to data from a wave gauge placed over the breakwater cross-section. Results confirmed that the video imagery technique is an alternative technique for measuring run-up in physical model experiments.

Neste artigo apresenta-se uma metodologia que visa minimizar os erros associados à medição por ADV (Acoustic Doppler Velocimetry). Estes erros podem ter duas causas: insuficiência de partículas em suspensão na coluna de água; e desalinhamento dos eixos do ADV com os eixos coordenados do problema. Seguindo esta metodologia, aplica-se primeiramente um filtro digital para eliminar as frequências elevadas fisicamente irrealistas e, em seguida, aplica-se uma transformação de coordenadas para alinhar as componentes de velocidade medidas com o sistema de coordenadas do problema, sendo possível identificar o desalinhamento do ADV face a esse sistema de coordenadas.Apresenta-se a aplicação desta metodologia na propagação de ondas regulares num canal.

Para a praia da Galé, Algarve, foram efetuados um conjunto de ensaios em modelo físico (canal de ondas) com o principal objetivo de analisar a hidrodinâmica da propagação de ondas sobre um fundo rochoso, para várias condições de agitação regular e irregular incidente. Efetuaram-se medições da elevação da superfície livre com sondas resistivas ao longo do canal e das componentes da velocidade com ADV, a meio da coluna de água em várias secções ao longo do canal. A evolução dos resultados ao longo do canal permite um melhor conhecimento do processo de propagação e contribui com dados para a validação de modelos numéricos.

Ships berthed inside sheltered basins can experience excessive movements due to waves. The paper presents an integrated numerical tool that interconnects several numerical models to reproduce the most relevant physical phenomena associated to wave action on a moored ship, the resulting ship movements and the forces on mooring lines and fenders. A new methodology was developed to determine the hydrodynamic forces on the ship.A non-linear phase resolving Boussinesq model is used to propagate waves from outside the harbour to wherever desired location inside the harbour. A modified version of a 3D panel method model computes the hydrodynamic coefficients of the ship, whereas the Haskind relations determine the wave forces on the ship. The time series of the moored ship motions and forces on moorings are obtained with another numerical model. This new methodology is used to replicate the scale model tests of a moored tanker inside Leixões Harbour.

Neste artigo, apresenta-se uma descrição do papel da modelação física no apoio aos estudos de Engenharia Costeira e Portuária, ilustrando-se as suas potencialidades com exemplos de casos de estudo.Referem-se os contributos inovadores em conceitos, equipamentos, técnicas e procedimentos experimentais que têm sido desenvolvidos nos recentes anos. Assim, apresentam-se metodologias a explorar no futuro, tais como procedimentos destinados a facilitar, agilizar e automatizar as análises de estabilidade e galgamentos de quebra-mares, assim como dos danos no manto protetor, provocados pela agitação marítima nele incidente, e o acesso remoto a ensaios experimentais, e à informação associada à realização destes, a clientes/investigadores interessados.Por fim, são apontados cenários de desenvolvimento para a modelação física de modo a lidar com as consequências das alterações climáticas, e que incorporem: a) sequências de eventos de temporal, incluindo efeitos cumulativos, b) a subida do nível médio do mar; c) técnicas de medição não intrusivas que permitam obter a análise de fenómenos complexos, com características de grande variabilidade temporal e espacial, sem interferir nos mesmos ou no próprio sistema modelado.

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A

N/A