Ermina Begovic

Roll Damping Coefficients Assessment and Comparison for Round Bilge and Hard Chine Hullforms

The sustainable design of small passenger vessels and large size pleasure craft indicates new trends: lower speed, reduced fuel consumption and better seakeeping in all range of velocities. Small amplitudes of roll motion are considered one of the most important comfort parameter. These trends call for reviewing some commonly used concepts and designer practice. Fundamental parameters as metacentric height and midsection form affect comfort as well as ship safety in counteracting way.Round bilge, due to good seakeeping characteristics and to large amount of available data from systematic series is the most common hull form choice when cruising speed implies displacement or semi displacement mode. Hard chine hull forms are generally chosen when relative speed leads to some hydrodynamic lift, although recently they have been considered for low relative speed. They allow simplified and cheaper construction and among their interesting features is higher roll damping. This appears very attractive for craft that are generally fitted with stabilizing systems and ask for the most reduced roll motions at any and zero speed.This paper presents the results of experimental tests relative to roll decay of two ship models of the same dimensions, displacement and GM values: they have the same warped bottom hull form developed at University of Naples, the first is hard chine and the second has round bilge from transom to midship. Both of them are suitable for displacement and semi-displacement craft operating at medium-low relative speed. The tests have been carried out at University of Naples towing tank, in calm water, at Fn ranging from 0.0 to 0.45. Natural roll frequencies and linear and non linear damping coefficients are reported for all tested speeds allowing a fair comparison of the roll characteristics due to the variation in hull form.Copyright

Co-operative investigation into resistance of different trimaran hull forms and configurations

Abstract This paper presents the results of a research program carried out on different trimaran hull forms and configurations suitable for medium size fast ferries. Resistance tests on large size scale models of the two different hull forms of main hull and outriggers, both isolated and combined in different configurations have been carried out at the towing tank of Naples University. For each isolated hull and trimaran configuration the total resistance and running trim have been assessed. Wave pattern analysis was also performed by experimental tests and by numerical computations, so that the influence of each resistance component has been highlighted. The results of this work could be used as a reference in trimaran hull design and optimization.

Zero emission sustainable craft for coastal Marine Protected Areas

This paper presents the results obtained by MArine HYdrodynamics Research Group of Department of Industrial Engineering (DII) at University of Naples regarding design and development of a zero emission craft for service in Mediterranean coastal Marine Protected Areas (MPA).