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- Physical modelling of motions and forces on a moored ship at the Leixões portPublication . Santos, João Alfredo; Pinheiro, Liliana; Abdelwahab, Hossam S.; Fortes, Conceição; Pedro, Francisco G. L.; Capitão, Rui P.; Hinostroza, Miguel; Soares, Carlos GuedesThis paper describes the physical model, experimental setup and tests performed at the Portuguese Civil Engineering Laboratory (LNEC), to study the motions and forces of a moored ship at the Leixões port, for different sea states in irregular waves. The tests were carried out at one of the wave tanks of LNEC, where the Leixões port layout was implemented at scale 1:80 with the detailed model similar to the prototype bathymetry and surrounding structures. The moored ship is a 3.43 m long scale model of the well-known “Esso Osaka” tanker and is moored to the pier A of the oil terminal at 0.135 m draft. Several types of measurements were recorded in this study. The freesurface elevation and wave direction were measured with a set of resistive wave gauges. The wave velocities at the entrance of the harbour were measured with an acoustic Doppler velocimeter. Motions of the moored ship were measured with the OptiTrack™ motion capture system whereas forces on fenders and mooring lines were measured with load cells attached to a complex spring system developed at LNEC. Several tests were carried out for a number of incident sea states characterized by a JONSWAP spectrum, with different significant wave heights and peak periods. The measurement, analysis and results obtained for the incident wave conditions characterized by a significant wave height of 6 m and a peak wave period of 14 s are presented and discussed in this paper.
- Modelação física e numérica da interação hidrodinâmica entre dois naviosPublication . Pedro, Francisco; Pinheiro, Liliana; Santos, João Alfredo; Fortes, Conceição J.E.M.; Hinostroza, MiguelNesta comunicação, analisa-se, recorrendo à modelação física e à modelação numérica, a interação hidrodinâmica entre dois navios, um dos quais parado, o navio “Esso Osaka”, e o outro em movimento, o navio “Aurora”. Os movimentos do navio parado são induzidos pela onda de esteira causada pelo outro navio que navega nas imediações daquele. Foram realizados testes para várias velocidades do navio em movimento, o Aurora, e para diferentes níveis de água. Efetua-se uma análise dos resultados obtidos para as diferentes condições de teste, quer da agitação gerada, quer dos movimentos induzidos no “Esso Osaka”. Relativamente à agitação gerada, as ondas de esteira, comparam-se os valores medidos com fórmulas empíricas da literatura. Finalmente, os movimentos registados são analisados e comparados, para algumas condições de teste, com os obtidos numericamente, recorrendo ao pacote numérico para simulação do comportamento de navios amarrados, SWAMS. Avalia-se o desempenho deste pacote numérico.
- Numerical and experimental studies on ship motions induced by passing shipPublication . Pedro, Francisco G.; Santos, João Alfredo; Pinheiro, Liliana; Fortes, Conceição J.; Hinostroza, MiguelTo investigate the ability of numerical models to simulate the behavior of moored ships subjected by ship-wake waves, use is made of scale model tests where a ship model sails with constant speed along a straight path at a constant distance from an otherwise motionless ship. The tests were carried out at one of the wave tanks of the Portuguese Civil Engineering Laboratory (LNEC). The moving ship is a self-propelled scale model of the "Aurora" chemical ship whereas the otherwise motionless ship is a scale model of the "Esso Osaka" tanker. The free-surface elevation was measured with a set of resistive wave gauges and ADVs. The tanker's movements, induced by the wake waves, were measured along the six degrees of freedom with a gyroscope deployed inside the ship. The numerical model WAMIT provides, in the frequency domain, the quantities required to estimate the hydrodynamic forces associated to the interaction of a free-floating ship with waves. The BAS model uses those hydrodynamic forces to study in the time domain the ship interaction with any sea-waves acting on it. Wind and current actions can also be accounted for. The results of these numerical models are compared to the measurements made in the several repeats of one of those scale model tests, in terms of the response amplitude to several wave components. These comparisons enabled the evaluation and validation of the numerical models parameters' calibration process.