engleski

New model for determination of seakeeping rank

Two basic characteristics of Bales’ model for ship rank determination are considered. The first one is the mutual division of average normalised response values for ship’s rank determination in particular response, which results with the rank values assignments to each ship which follow the hyperbolic rule. Furthermore, when some of average normalised response values equal zero, the operation of dividing zero with a real number creates a problem. The second značajka is the scaling of the rank values between one and ten, one for the worst and ten for the best ship with respect to seakeeping perfomance in considered group of ships. In this way the values of seakeeping rank are made relative. In order to remove the above-listed deficiencies a new model for determination of seakeeping rank has been defined. This model gives a linear relation between the rank value and the average normalised response values. In this model the operation of dividing zero with a real number is avoided and considered ships are compared with two imaginary ships: an ideal one, with all response values equal to zero, and the bad one, with the greatest response values found in all considered types of responses. Both models for the determining of seakeeping rank are mathematically defined, and the seakeeping ranks for three fleets with 27 ships each, having a displacement of 1000, 1500 and 2000 tons respectively, have been calculated. The analysis of these rank values shows the influence of displacement and of the new definition of rank in particular response on the value of the seakeeping rank of a ship, and respectively on the order of the ranked ships. The results of the analysis, illustrated with charts, show the benefits of this new model compared to Bales’ model.

ship's form; seakeeping rank

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