A methodology for evaluating the controllability of a ship navigating in a restricted channel

A methodology is presented for evaluating the controllability of a ship navigating in a restricted channel by means of a hydrodynamic force analysis. This method is applied to assess the controllability of a container vessel in straight channel reaches and in bends in two practical cases. By comparing different initial conditions and bottom configurations the influence of different ship characteristics (main dimensions, draft, rudder and propeller characteristics), operational parameters (such as speed, propeller commands, and bank clearance), environmental parameters (such as current and tidal level), and channel characteristics (water depth, bank slope, bend radius) on this controllability can be evaluated. For estimating the components of the force analysis, use is made of results of captive model tests in shallow and restricted waters

An overview of squat measurements for container ships in restricted water

Squat is an important issue for ships navigating with limited under keel clearance in restricted waterways such aschannels and canals. The admittance policy for containerships on the Western Scheldt, a tidal estuary in theNetherlands giving access to the port of Antwerp (Belgium), is based on a minimal static under keel clearance toensure safe passages on the river. A large number of captive model tests executed in the Towing Tank forManoeuvres in Shallow Water (co-operation Flanders Hydraulics Research - Ghent University) have beenevaluated to determine squat prediction formulae. Measured sinkage and trim depend on a number of parameterslike ship velocity components, ship loading condition, propeller action, blockage of the waterway, bankgeometries and characteristics of other shipping traffic. The derived mathematical models have beenimplemented in the ship manoeuvring simulators of FHR to visualize the dynamic under keel clearance duringreal-time simulations at different locations on the Western Scheldt

Numerical modelling of wave energy absorption by a floating point absorber system [POSTER]

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Optimal pattern of interacting wave power devices

The contribution of Wave Energy Converters (WECs) to the renewable energy supply is continuously rising. To produce a considerable amount of electricity, wave power devices or WECs need to be placed in a farm.In a farm WECs interact and the amount of produced electricity is affected to a certain extent, depending on the lay-out of the farm. In order to find the optimal lay-out WECs are studied in a numerical mild-slope type model, generally used for wave propagation in coastal applications. The existing model is adapted by simulating the energy extraction of a WEC through sponge layers.The adjusted model can be used to study the optimal lay-out and electricity production of a farm

A comparison of experimental and numerical behaviour characteristics of a ship entering a lock using benchmark test data

This paper discusses several papers that were presented at the 3rd International Conference on Ship Manoeuvring in Shallow and Confined Water, which had a non-exclusive focus on Ship Behaviour in Locks. For this conference, experimental model test data obtained at Flanders Hydraulics Research had been made public and researchers were encouraged to compare numerical with experimental results [1]. Data of benchmark tests carried out both with self-propelled and captive models were used by researchers for comparison with various numerical tools. The objective of this paper is to give a selected overview of how accurately numerical tools are presently able to predict the hydrodynamic forces that occur on ships approaching locks. Based on this, the paper concludes that experiments and numerical tools complement each other

Bottom slamming on heaving point absorber wave energy devices

Oscillating point absorber buoys may rise out of the water and be subjected to bottom slamming upon re-entering the water. Numerical simulations are performed to estimate the power absorption, the impact velocities and the corresponding slamming forces for various slamming constraints. Three buoy shapes are considered: a hemisphere and two conical shapes with deadrise angles of 30 and 45, with a waterline diameter of 5 m. The simulations indicate that the risk of rising out of the water is largely dependent on the buoy draft and sea state. Although associated with power losses, emergence occurrence probabilities can be significantly reduced by adapting the control parameters. The magnitude of the slamming load is severely influenced by the buoy shape. The ratio between the peak impact load on the hemisphere and that on the 45 cone is approximately 2, whereas the power absorption is only 4-8% higher for the 45° cone. This work illustrates the need to include slamming considerations aside from power absorption criteria in the buoy shape design process and the control strategy

Investigation of vertical slamming on point absorbers

This paper focuses on the impact of vertical slamming on floating point absorber systems and the associated pressures that might be expected when these phenomena occur. In a first part it will be shown how the occurrence probability of slamming can be reduced by implementing a slamming restriction, i.e. by controlling the motion of the point absorber. The impact of these slamming restrictions on power absorption will be discussed. Secondly an investigation is made of the pressures that occur when the buoys are subject to vertical bottom slamming. Analytical results are presented, which give a pressure prediction of an impacting body with conical and hemispherical shape, using Wagner theory. Laboratory experiments have been carried out at Ghent University. Impact pressures were measured during drop tests with both hemispherical and conical buoy shapes. These pressures were measured by ICP pressure sensors with a range up to 345 kPa with small membrane and very high resonance frequency (> 250 kHz). Analytical and physical results are compared and conclusions are drawn

Tank test of vessel entry and exit for third set of Panama locks

The Panama Canal Authority (ACP) plans to extend the capacity of and allow larger ships to the Canal by building a so-called third lane, consisting of a new set of locks parallel to the existing ones. The design ship is a so-called Post-Panamax 12000 TEU container carrier. In order to optimise the approach to and the manoeuvres within the locks, in 2007-2008 experimental research has been conducted at Flanders Hydraulics Research, Antwerp, Belgium on a 1/80 scale model of the approach lane, the lock and the design vessel. With the ship model moving along a guiding rail, lateral forces acting on the ship and movements of the vessel can be recorded during a selection of entrance and exit manoeuvres. During a number of tests, the effect of density exchange current was examined. The present article offers an overview of the test-setup with a discussion of a few interesting results of the test runs