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- Experimental and numerical simulations of oblique extreme wave conditions in front of a breakwater`s trunk and round headPublication . Carvalho, R. F.; Santos, João Alfredo; Ojeda, G. Barajas; Beg, Md. N. A.; Lopes, P. M.; Fortes, J. C.; Lara, J. L.Climate change studies already reported sea level rise as an accepted scenario, which induces changes in nearshore wave conditions. A large range of new experiences including water level, run-up, overtopping, hydrodynamic data for different wave steepnesses and directions was performed in the Leibniz Universität Hannover (LUH) wave basin for a rubble mound breakwater with a slope of 1(V):2(H). This work presents, focusing on oblique extreme wave conditions, numerical simulations of the hydrodynamics in that experiment using OpenFOAM®. Results of the wave generation boundary conditions and their propagation, namely elevation of the water level free-surface and velocity data at specific locations are compared and discussed with data from experimental measurements acquired by acoustic wave gauges and acoustic doppler velocimeter (ADV) / Vectrino equipment. Although an exact match between numerical and laboratory values was not reached, an appropriate incident wave angle and a reasonable amplitude of velocities and water depths was achieved and the same happened to the statistics of those values.
- Experimental study of an onshore dual chamber oscillating water column devicePublication . Gadelho, Jorge; Rezanejad, Kourosh; Guedes Soares, Carlos; Santos, João Alfredo; Anastas, Gael; Fortes, ConceiçãoA wave flume is used to study a scaled model of a stepped bottom dual-chamber Oscillating Water Column (OWC) installed onshore. Compared to traditional single-chamber OWCs, the use of dual-chambers is expected to widen the range of sea states in which the OWC is more efficient, and the step, in front of the first chamber, boosts the capturing energy capacity of the device. The Power Take-Off (PTO) system is modelled as an air opening in the pneumatic chambers. Several experiments combining regular incident waves and PTO damping conditions are performed. Results of the amplitudes of the free surface elevations inside the chambers show that the device can amplify the incident wave amplitude up to 1.57 times in chamber 2. Results of the primary ef ficiency show that the device is highly dependent on the PTO damping characteristics and can reach around 40% for a wide range of wave periods. Results of the reflection analysis show that the reflection coefficient is also dependent on the PTO damping characteristics but remain lower than 0.6 for all the studied cases. Sloshing phenomenon (mostly in the cross-section direction) was observed for a wavelength close to the cross-section dimension, impacting negatively on the device pneumatic performance.
- Desenvolvimentos iniciais do projeto To-SEAlert: galgamento e inundação em zonas portuárias e costeirasPublication . Fortes, Conceição; Reis, Maria Teresa; Santos, João Alfredo; Poseiro, Pedro; CAPITÃO, RUI; Pinheiro, Liliana; Lemos, Rute; Fonseca, Ana; Barateiro, José; Serrazina, Vera; Craveiro, João; Ferreira, José Carlos; Duarte, Cláudio Macedo; Andriolo, Umberto; Taborda, Rui; Silva, Ana; Lara, JavierO 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.
- Simulation of wave action on a moored container carrier inside Sines’ HarbourPublication . Pinheiro, L.; Fortes, C. J. E. M.; Jalles, B. M. Abecassis; Santos, João Alfredo; Fernandes, Luís MiguelThe integrated numerical tool SWAMS (Simulation of Wave Action on Moored Ships) is used to simulate the behavior of a moored container carrier inside Sines’ Harbour. Wave, wind, currents, floating ship and moorings interaction is discussed. Several case scenarios are compared differing in the layout of the harbour and wind and wave conditions. The several harbour layouts correspond to proposed alternatives for the future expansion of Sines’ terminal XXI that include the extension of the East breakwater and of the quay. Additionally, the influence of wind on the behavior of the ship moored and the introduction of pre tensioning the mooring lines was analyzed. Hydrodynamic forces acting on the ship are determined using a modified version of the WAMIT model. This modified model utilizes the Haskind relations and the non-linear wave field inside the harbour obtained with finite element numerical model, BOUSS-WMH (Boussinesq Wave Model for Harbors) to get the wave forces on the ship. The time series of the moored ship motions and forces on moorings are obtained using BAS solver. © 2015 Taylor & Francis Group, London.
- Energy assessment of potential locations for OWC instalation at the Portuguese coastPublication . Anastas, Gael; Santos, João Alfredo; Fortes, C. J. E. M.; Pinheiro, LilianaThis work aims to determine the exploitable wave energy resource at five potential sites close to harbour pro-tection facilities at the Portuguese coast, namely at the Azores archipelago, at Madeira Island and at Sines, on the coast of mainland Portugal. For that purpose, a third-generation wave model SWAN is used to transfer the offshore estimates of sea wave conditions to those points over the last 40 years. Sea states and wind fields are provided by the climate reanalysis datasets ERA5. Using sea states as boundary conditions and wind fields as forcings in the numerical domains of the SWAN model, the sea states were propagated shoreward, in order to estimate and analyse the wave 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 analysed since it is of paramount importance for the efficiency of Wave Energy Converters (WEC). This assessment showed that the best location for the installation of dual-chamber OWC devices is at the Azores archipelago.
- Numerical and experimental study of ship-generated wavesPublication . Rodrigues, Sara; Guedes Soares, Carlos; Santos, João AlfredoThis paper presents the results of the numerical and experimental study on the propagation of ship-generated waves. In the numerical modified FUNWAVE code, which is able to reproduce most of the phenomena involved in wave propagation, the ship is represented by a moving pressure distribution function at the free surface. The experimental tests were carried out with a ship model at a 1: 50 scale that moving at constant speed across a constant depth region. The values of wave heights obtained in the scale ship model 1: 50 were used to compare with the predictions of wave heights provided by the numerical code. The comparison of the results obtained by the numerical code and the experimental tests shows very similar values for the maximum wave height.
- Integrated analysis of climate, soil, topography and vegetative growth in Iberian viticultural regionsPublication . Fraga, Hélder; Malheiro, Aureliano C.; Moutinho-Pereira, José; Cardoso, Rita M.; Soares, Pedro Miguel Matos; Cancela, Javier J; Pinto, Joaquim G.; Santos, João AlfredoThe Iberian viticultural regions are convened according to the Denomination of Origin (DO) and present different climates, soils, topography and management practices. All these elements influence the vegetative growth of different varieties throughout the peninsula, and are tied to grape quality and wine type. In the current study, an integrated analysis of climate, soil, topography and vegetative growth was performed for the Iberian DO regions, using state-of-the-art datasets. For climatic assessment, a categorized index, accounting for phenological/thermal development, water availability and grape ripening conditions was computed. Soil textural classes were established to distinguish soil types. Elevation and aspect (orientation) were also taken into account, as the leading topographic elements. A spectral vegetation index was used to assess grapevine vegetative growth and an integrated analysis of all variables was performed. The results showed that the integrated climate-soil-topography influence on vine performance is evident. Most Iberian vineyards are grown in temperate dry climates with loamy soils, presenting low vegetative growth. Vineyards in temperate humid conditions tend to show higher vegetative growth. Conversely, in cooler/warmer climates, lower vigour vineyards prevail and other factors, such as soil type and precipitation acquire more important roles in driving vigour. Vines in prevailing loamy soils are grown over a wide climatic diversity, suggesting that precipitation is the primary factor influencing vigour. The present assessment of terroir characteristics allows direct comparison among wine regions and may have great value to viticulturists, particularly under a changing climate.
- Coupling numerical models for wave propagation in the MOIA packagePublication . Santos, João Alfredo; Guilherme, L.; Fortes, C. J.; Pinheiro, L.; Simões, A.Sea wave action is a key factor for several aspects of port activities. Numerical models for wave forecasting at a regional level can produce quite accurate estimates of the sea state characteristics offshore a given port. There is a research project going on, code-named MOIA, that aims at developing an integrated toot to support the management of port activities by taking into account the effects of waves on some of those activities. To characterize sea waves inside a given port use is made of a set of coupled models that propagate the values that were measured or predicted off the port. The starting point is a tool developed at LNEC, SOPRO, which incorporates several of such numerical models. The paper describes the progress done so far in the coupling of the several numerical models that enable the propagation of the sea-state characteristics forecast off the Praia da Vitoria port (Terceira, Azores) up to the port terminals.
- Risk analysis and management of moored ships in portsPublication . Pinheiro, Liliana; Fortes, Conceição J. E. M.; Santos, João AlfredoThe risks associated with mooring of ships are a major concern for port and maritime authorities. Sea waves and extreme weather conditions can lead to excessive movements of vessels and mooring loads affecting the safety of ships, cargo, passengers, crew or port infrastructures. Normally, port activities such as ships' approach manoeuvres and loading/unloading operations, are conditioned or suspended based solely on weather or wave forecasts, causing large economic losses. Nevertheless, it has been shown that some of the most hazardous events with moored ships happen on days with mild sea and wind conditions, being the culprit long waves and resonance phenomena. Bad weather conditions can be managed with an appropriate or reinforced mooring arrangement. A correct risk assessment must be based on the movements of the ship and on the mooring loads, taking into account all the moored ship's system. In this paper, the development of a forecast and warning system based on the assessment of risks associated with moored ships in port areas, SWAMS ALERT, is detailed. This modular system can be scaled and adapted to any port, providing decision-makers with accurate and complete information on the behaviour of moored ships, movements and mooring loads, allowing a better planning and integrated management of port areas.
- Propagation of waves generated by a pressure disturbance moving in a channelPublication . Rodrigues, S. R. A.; Soares, C. Guedes; Santos, João AlfredoThis paper studies the effect of ship speed and water depth on the propagation of ship generated waves. The ship is represented by a moving pressure distribution function at the free surface that is able to reproduce most of the phenomena involved in wave propagation. Results are obtained for a ship sailing along a coastal stretch made of a sloping bottom and a constant depth region. The results show that in the sloping bottom the crests of waves are bent along the slope and in the constant depth the standard Kelvin wave patterns can be found for the subcritical regime. In the critical regime the wave system is characterized by significant diverging waves and for a supercritical regime, the transverse waves disappear. © 2015 Taylor & Francis Group, London.