Wave effects on the turning ability of an ultra large container ship in shallow water

The influence of waves on ship behaviour can lead to hazardous scenarios which put at risk the ship, the crew and the surroundings. For this reason, investigating the effect of waves on manoeuvring is of relevant interest. Waves may impair the overall manoeuvring performance of ships hence increasing risks such as collisions, which are of critical importance when considering dense traffic around harbour entrances and in unsheltered access channels. These are conditions met by Ultra Large Container Ships (ULCS) when approaching a port, e.g. in the North Sea access channels to the main sea ports of Belgium. Note that due to the large draft of ULCS and the limited water depth, shallow water effects will also influenced the ship. Thus, in such scenarios the combined effects of shallow water and waves on the ship's manoeuvring need to be studied. The present work investigates the effect of waves on the turning ability of an ULCS in shallow water. Simulations are carried out using the two time scale approach. The restricted water depth corresponds to 50% Under Keel Clearance (UKC). To gain a better insight on the forces acting on the ship, the propulsion, and the rudder behaviour in waves experimental studies were conducted. These tests were carried out in the Towing Tank for Manoeuvres in Confined Water at Flanders Hydraulics Research (in co-operation with Ghent University) with a scale model of an ULCS. Different wave lengths, wave amplitudes, ships speeds, propeller rates, and rudder angles were tested. The turning ability characteristics obtained from simulations in waves and calm water are presented, and discussed

Full-scale measurement to assess squat and vertical motions in exposed shallow water

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Full-scale measurements of vertical motions on ultra large container vessels in Scheldt Estuary

From September 2017 to July 2018 the Flemish Pilotage executed nine ship measurements on container ships to and from Antwerp. The measurement results were processed by Flanders Hydraulics Research and Ghent University providing 6 DoF motions of the vessels. Furthermore environmental data regarding tide, currents, waves, bathymetry and AIS were processed in order to assess the influence of environmental conditions on the vertical motions of container ships. The paper presents the vertical ship motions separately for steady and unsteady sinkages in different DoF. As such the relation with ship squat, hydrostatics, sea keeping, turning, steering and ship-to-ship interaction could be assessed and related to the driving parameters such as ship speed, rate of turn, under keel clearance, water density, waves, rudder action and ship meetings

Ship manoeuvring model parameter identification using intelligent machine learning method and the beetle antennae search algorithm

In order to identify more accurately and efficiently the unknown parameters of a ship motions model, a novel Nonlinear Least Squares Support Vector Machine (NLSSVM) algorithm, whose penalty factor and Radial Basis Function (RBF) kernel parameters are optimised by the Beetle Antennae Search algorithm (BAS), is proposed and investigated Aiming at validating the accuracy and applicability of the proposed method, the method is employed to identify the linear and nonlinear parameters of the first-order nonlinear Nomoto model with training samples from numerical simulation and experimental data. Subsequently, the identified parameters are applied in predicting the ship motion. The predicted results illustrate that the new NLSSVM-BAS algorithm can be applied in identifying ship motion's model, and the effectiveness is verified. Compared among traditional identification approaches with the proposed method, the results display that the accuracy is improved. Moreover, the robust and stability of the NLSSVM-BAS are verified by adding noise in the training sample data