Jeroen Verwilligen

Ship Motions in Shallow Water As the Base for a Probabilistic Approach Policy

A calculation tool has been developed for determining tidal windows for deep-drafted ships approaching and leaving the Belgian harbors according to probabilistic criteria. The calculations are based on a database containing response functions for the vertical motions in waves and squat data for a selection of representative ships. The database contains both results of model tests carried out in the Towing tank for maneuvers in shallow water – co-operation Flanders Hydraulics Research & Ghent University in Antwerp (Belgium), as well as calculated values. During the experiments, draft, trim, under keel clearance (7 to 20% of draft) and speed have been varied. The tests were performed in regular waves with lengths which are small compared to ship length, and in wave spectra that are typical for the Belgian coastal area. For given input data (ship characteristics, speed, tide, directional wave spectra, bottom, trajectory, current, departure time), the tool calculates the probability of bottom touch during the transit, so that a tidal window can be determined. Other restrictions, such as penetration into fluid mud layers and current, are taken into account as well.Copyright

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.