Publications

Knowledge of forces due to the action of waves on submarine outfalls composed by a pipe and stabilizing concrete weights, considering the wave propagation direction to the outfalls, is essential to their design. 3D numerical models based on RANS-VoF (Reynolds-Average-Navier-Stokes Volume-of-Fluid) are able to estimate forces on the pipe and weights. The present study aims to simulate a submarine outfall with stabilizing concrete weights at 1:15 scale which was previously tested in the 3D Shallow Water Basin at the Danish Hydraulics Institute (DHI) to analyse the influence of the direction of the incident wave and the distance from the pipe to the bottom on the outfall forces. In this study, numerical results are compared with experimental ones for waves with four different amplitudes and with wave incidence perpendicular to the outfall. The use of k-

The aim of this paper is the experimental characterization of the capture width ratio (CWR) and response amplitude operator (RAO) of a 1:10 physical model of an oscillating wave surge converter (OWSC), under unidirectional regular and irregular waves. The effects of hydraulic power take-off (PTO) system are explicitly taken in consideration. A mathematical model is proposed to describe the PTO damping as a function of the angular velocity of the flap. The harmonic decomposition of free-surface elevation, angular velocity of the flap and pressure in the PTO system demonstrates that these signals are dominated by their linear component. However, the signals also present some important higher-order frequency components. To predict the CWR of the OWSC under irregular waves the nonlinear output frequency response functions are considered as the extension of the RAO to the nonlinear case. It is shown and discussed that the PTO system, wave frequency and height have a significant influence on the CWR and RAO. The RAO curve for irregular waves does not exhibit a well-defined peak, showing a limited variation in a broadband. A weak correlation between CWR and RAO was found, i.e., the maximum CWR does not occur for the maximum value of RAO.

Fluid-dynamic interference among cylindrical structures in arrays, frequently used in engineering, is of fundamental and practical interests since it may considerably change fluid-structure interactions and produce large fluctuating forces on structures that cause vibrations, lock-in and important motions. This paper aims to study the mutual interference between two circular cylinders in tandem arrangement, which is considered the simplest configuration of one array cylinders, elastically mounted in transversal direction and subject to a bi-dimensional uniform laminar flow at low Reynolds numbers. Both cylinders have the same diameter D and the center-to-center spacing is equal to L = 5.25D which corresponds to co-shedding regime. The academic numerical model Ifeinco, which is based on the finite element method and uses a partitioned scheme that considers two-way interaction of fluid flow and structure, has been employed to the analysis. Combinations of upstream and downstream stationary and elastically mounted cylinders are investigated for Reynolds number range from 90 to 140. Differences of flow behaviors drag and lift forces and resonance between single cylinder and cylinders in tandem arrangement were found. Mutual and respective influence of upstream cylinder motion on the downstream cylinder and vice-versa are analyzed. Results show that, in some engineering studies, the consideration of the flexibility of cylindrical structures in arrays is fundamental since it influences significantly the interference between cylinders, mainly the magnitude and direction of forces and characteristics of the resonance range, and, consequently, structural and dynamical behaviors.

This paper describes a programme under the responsibility of the National Laboratory for Civil Engineering (LNEC), Portugal for the systematic observation and monitoring of maritime works, termed OSOM+, which has been applied to an extensive number of maritime structures on the Portuguese mainland coast and abroad. The OSOM+ programme comprises the following four main components for each structure: a) Periodic visual inspections by a trained technician; b) Periodic aerial inspections using a UAV/drone; c) The ANOSOM-GIS database, to store and/or query obtained information, as well as to diagnose present, evolution and risk conditions; and d) A mobile, portable, application, for real-time input and visualization of the ANOSOM-GIS database information.This recently updated methodology encompasses a number of tools whose functionalities are illustrated in this paper with an application to a case study: the Ericeira

This paper describes a methodology to determine the optimal size of a Wells turbine to be used in an OWC device taking into account hydro-aerodynamic coupling, performance curves of the turbine and air pressure control by a relief valve. The proposed model, named turbine diameter optimization (TDO) model, considers the movement of the water surface inside the OWC chamber as a piston movement in response to the hydrodynamic forces from the incoming waves. The aerodynamic is based on the first law of thermodynamics applied to the air column of the chamber. The power-pressure curve of the turbine and the air pressure control by relief valve are implemented in the model to determine the turbine power output for several regular incident waves. The TDO model is initially calibrated by a numerical model based on Reynolds-Average-Navier-Stokes (RANS) equations for each wave component of an expected sea state distribution. Thereafter, the power output generated by turbines of several sizes is calculated with lower computational cost (few minutes) in comparison with RANS based models (thousands of hours) in a personal computer. This developed methodology is an important support to the process of turbine sizing for an OWC device for an expected sea state distribution.

This paper describes the preliminary developments of an innovative integrated tool for the numerical modelling of oscillating water column (OWC) wave energy converters (WEC) integrated in vertical breakwaters. The main purpose of the tool is the numerical modelling of wave propagation from offshore to nearshore, wave-structure interaction, and the complex nonlinear hydrodynamic and aerodynamic phenomena that occur in OWC-WECs.The tool development and validation were supported by experimental data from physical model tests carried out in a wave flume at the Portuguese National Laboratory for Civil Engineering (LNEC). Prototype data were also available for the Pico OWC-WEC in the Azores, Portugal, monitored by the Portuguese Wave Energy Centre since 2005. Application of the tool for sea-wave characterization at the Azores archipelago and calculation of the corresponding wave power for a period of 10 years at various points around each island show that, in winter, there is good availability of wave energy in most quadrants of each island. In summer, the resource exploitation is only worthwhile on the north-west coasts of the islands. Physical and numerical modelling results for an OWC with a fully open chamber show good agreement between experimental data and numerical values for several incident wave conditions. The analysed results include the time series of the free-surface elevation at different locations, the time series of the mean free surface inside the water chamber, the amplification factors, the phase angles and the velocity vectors at the highest and the lowest positions of the mean free surface inside the chamber. The tool showed its potential to be useful in supporting ocean and coastal engineering projects due to its capacity to effectively reproduce the main phenomena involved in these types of studies.

Joint statistical models for long-term wave climate are a key aspect of offshore wind engineering design. However, to find a joint model for sea-state characteristics is often difficult due to the complex nature of the wave climate and the physical constraints of seastates phenomena. The available records of wave heights and periods are often very asymmetric in their nature. This article presents a copula-based approach to obtain the joint cumulative distribution function of the significant wave heights and the up-crossing mean period. This study is based on 124-month hindcast data concerning Horns Rev 3 offshore wind farm. The extra-parametrization technique of symmetric copulas is implemented to account for the asymmetry present in the data. The analysis of the total sea, the wind-sea and primary swell components is performed separately. The results show that the extra-parametrization technique with pairwise copulas consistently provided a better goodness-of-fit when compared to symmetric copulas. Moreover, it is demonstrated that the separation of the total sea into its components does not always improve the extra-parametrized copula

This paper analyses the hydrodynamic interaction between two ships, one stationary and the other navigating nearby, using physical and numerical modelling. The passing ship is a self-propelled scale model of the

The global warming is responsible for increasing the sea level and, consequently, can cause overtopping on coastal structures. The prediction of this phenomenon is difficult because involves turbulence, wave breaking and run-up. The objective of this study is to analyze numerically the wave overtopping on coastal structures by using the FLUENT® numerical model, which is based on Reynolds-Averaged Navier-Stokes equations (RANS) and uses the Volume of Fluid method (VoF) to track the interface between water and air. Influences of mesh size, turbulence model (k-

Os quebra-mares de talude são estruturas normalmente utilizadas para proteção costeira e portuária e estão sujeitas durante a sua vida útil a diferentes solicitações (p.e., agitação marítima). A avaliação do seu estado estrutural e a previsão do seu comportamento ao longo do tempo torna-se fundamental para evitar significativos prejuízos materiais. É nesse âmbito que se insere o programa de observação sistemática, em curso no LNEC, desde 1986, para quebra-mares localizados em Portugal Continental, nos quais o Laboratório Nacional de Engenharia Civil (LNEC) realiza inspeções periódicas e avalia as respetivas condições de segurança. Para apoio a esse programa foi densenvolvida no LNEC a aplicação ANOSOM, a qual tem sofrido, ao longo dos tempos, diversas atualizações com vista a acompanhar a evolução que o programa OSOM+ tem vindo a sofrer. Esta comunicação descreve as funcionalidades da mais recente versão desta aplicação, a ANOSOM-WEB, como ferramenta de gestão de risco em estruturas de proteção costeira.

Regarding the stability of armour layers, several authors have proposed guidelines on how toconsider the effects of oblique waves (e.g. Yu et al., 2002, Van Gent, 2014; Maciñeira &Burcharth, 2016). Especially for very oblique waves, for which the increase in stability is thelargest, limited data are available. Under the scope of the HYDRALAB+ transnational accessproject

O desenvolvimento de capacidade para prever a agitação marítima ao nível das bacias oceânicas com alguns dias de antecedência estimulou o aparecimento de sistemas informáticos para previsão dos efeitos da agitação marítima em zonas costeiras e portuárias. O HIDRALERTA é um desses sistemas: partindo das características da agitação marítima ao largo e utilizando modelos numéricos para a propagação da agitação marítima estima os parâmetros relevantes da agitação marítima para a avaliação do galgamento e do espraiamento quer em zonas portuárias, quer em zonas costeiras. 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 pretende melhorar as funcionalidades daquele sistema no que se refere às metodologias de previsão do galgamento e da delimitação da zona inundada, bem como no apoio à resposta a situações de emergência envolvendo aquele fenómeno.Esta comunicação pretende descrever o racional que justifica a existência do projeto, as tarefas em que o mesmo foi dividido e os principais resultados esperados.

Neste artigo descreve-se a metodologia atualmente existente no Laboratório Nacional de Engenharia Civil (LNEC) de observação e monitorização sistemática de obras marítimas, que tem sido aplicada com sucesso a um grande número de estruturas marítimas na costa continental portuguesa e no estrangeiro.A atual metodologia (OSOM+) de diagnóstico de quebra-mares para avaliação dos estados atual, de evolução e de risco, complementa a anterior (OSOM), baseada somente em observações visuais, utilizando agora também a informação obtida com as inspeções com drone. Os resultados obtidos com as observações de drone, nomeadamente as fotografias aéreas verticais, os ortomosaicos e a nuvens de pontos, a partir das quais são construídos os modelos digitais de superfície das estruturas, permitem melhor avaliação do dano.Para ilustrar a aplicação da atual metodologia de avaliação de segurança de quebra-mares, usam-se os resultados da campanha de levantamento aéreo realizada em setembro de 2018 no quebra-mar poente da entrada do porto de Portimão.

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.

A caraterização da rebentação / espraiamento / galgamento e do seu impacto na estabilidade de quebra-mares de taludes, quer no tronco, quer na cabeça, ainda é deficiente para cenários de alterações climáticas. O mesmo acontece com a influência nestes fenómenos de grandes ângulos de incidência da agitação marítima. A experiência RODBreak envolveu uma equipa de 23 pessoas de 8 instituições europeias e pretendeu criar um conjunto de dados para:- estender ou melhorar a gama de validade das fórmulas empíricas existentes para a estabilidade do manto protetor, o que facilitará a avaliação do desempenho das estruturas existentes;- calibrar e validar fórmulas empíricas para o espraiamento e galgamento, bem como modelos numéricos para a interação onda-estrutura.Além disso, esta foi uma oportunidade única para testar e melhorar algumas técnicas não intrusivas para medir quantidades relacionadas com aqueles fenómenos. Esta comunicação descreve os testes realizados no tanque de ondas 3D do Ludwig-Franzius-Institut für Wasserbau, Ästuar- und Kusteningenieurwesen da Leibnitz Universität Hannover em outubro e novembro de 2017.

O Porto de Leixões, localizado na costa norte de Portugal, é um dos maiores do país, recebendo diariamente um grande número de navios de grandes dimensões. Um dos principais postos de acostagem situa-se à entrada do porto e encontra-se sujeito à agitação marítima que é difratada pelo olhe principal de proteção do porto. Para avaliar dos movimentos induzidos no navio estacionado nesse posto de acostagem e as forças exercidas nas suas amarras e defensas pela agitação incidente, utilizou-se o modelo físico de Leixões, construído num dos tanques do LNEC. Neste modelo físico, encontra-se representada a envolvente do porto de Leixões, assim como a sua batimetria. O modelo do navio

Under the framework of the ECOMAPORT project, two new prototypes of the forecast, early warning and risk management HIDRALERTA system to the ports of Madalena do Pico and S. Roque do Pico, both on the Island of Pico, Azores are undergoing. Those prototypes are intended to assess and predict, on a regular basis, the risk of coastal overtopping and consequent flooding and the risk to navigation, in particular as regards the safety of moored and maneuvered vessels, both caused by wave agitation. Additionally, it is intended to guarantee the functionality of the prototype of the HIDRALERTA system currently implemented in the port of Praia da Vitória, in Terceira Island, Azores since 2015, and to implement a new aspect regarding navigation risk.The new prototypes are based on the methodology already developed for the port of Praia da Vitória, where the first prototype of the HIDRALERTA system has been in operation since 2015.This paper essentially describes the work carried out to date on the system and their application to the ports of S. Roque do Pico and Madalena do Pico.

This paper presents a set of scale-model tests carried out to extend the range of wave steepness values analyzed in wave run-up, overtopping and armour layer stability studies, focusing on oblique extreme wave conditions and on their effects on a gently sloping breakwater trunk armour and roundhead. A stretch of a rubble-mound breakwater (head and part of the adjoining trunk, with a slope of 1(V):2(H)) was built in a wave basin at the Leibnitz Universität Hannover to assess, under extreme wave conditions (wave steepness of 0.055) with different incident wave angles (from 40º to 90º), the structure behaviour in what concerns wave run-up, wave overtopping and damage progression of the armour layers, composed by rock and Antifer cubes. Non-intrusive methodologies were used for the assessment of armour layer damage evolution, including a laser scanning technique, stereo photogrammetry and a Kinect© motion sensor. The aim of the present work is to characterize damage evolution, based upon surveys carried out with the Kinect© motion sensor, for 4 of the 11 test series conducted during the test program.

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