International Shipbuilding Progress - Volume 49, issue 2

Authors: Sternsson, Mikael | Bjökenstam, Ulf

Article Type: Research Article

Abstract: Recordings of wave data measured on-board a PCTC vessel were evaluated and compared with traditional global wave statistics. The influence of the handling of the ship, such as weather routing, on avoiding bad weather conditions was particularly studied. It was shown that the probability of significant wave heights in the region of 7–14 meters decreased considerably, as compared with well-known wave statistics, while extreme wave heights with return periods of 10 years or more decreased only …slightly. Show more

Keywords: weather routing, wave statistics, extreme waves

Citation: International Shipbuilding Progress, vol. 49, no. 2, pp. 85-94, 2002

Authors: Subramanian, V. Anantha | Beena, V.I.

Article Type: Research Article

Abstract: This paper describes a quick method of surface modelling coupled with interactive fairing of the SWATH hull based on 'optimal' geometry based inputs. This design approach is used for hydrodynamic evaluation to obtain motion and dynamic effects. A combination of typical hull form variants is assessed to obtain relative merits. In the absence of large database support from past experience, it is necessary to have a more fundamental approach to designing the SWATH form. This paper …reports the use of hitherto accepted polynomial coefficients (Chebychev's polynomial) to link the basic owner's requirements with optimal geometry based characteristics such as displacement, centre of buoyancy, centre of flotation, distribution of strut waterplane area and underwater displacement hull sectional area. Once these are obtained, a computer based form generation scheme is deployed for generation of the hull form. The scheme uses bi-quintic B-splines (Basis splines) with their characteristic features of flexibility and controllability as an important tool in the representation of the body surface. Since the B-spline shape is influenced by the knot vector and the order of the curve, the obtained form is capable of being changed locally by removal or insertion of knots (KR – KI algorithm). This algorithm helps in controlling not only local section shapes, but also formation or elimination of knuckles or sharp corners such as the joint of strut and lower hull or upper hull. Application of this new method to typical SWATH forms with circular, elliptical or 'golf club' section shapes or any arbitrary variation of sectional area distribution is demonstrated. Coarse grid inputs for the polygon net enable development of the targetted form. The technique is illustrated through different stages of development of the hull form. The obtained form is subjected to hydrodynamic performance analysis using a package. Performance based on different basic section shapes and different sectional area distribution curves is evaluated for stationary and speed conditions. The results bring out relative merits of the hull forms and provide insights on their intrinsic advantages. The method serves as a rapid assessment tool in preliminary design. Show more

Citation: International Shipbuilding Progress, vol. 49, no. 2, pp. 95-125, 2002

Authors: Markovina, Roko

Article Type: Research Article

Abstract: In the paper, some thinking has been given on needs and possibilities of modern super-high-speed vessel. This idea refers to the preliminary design for "GLIDING WING" as a vessel with the speed over 100 knots, with flying and landing possibilities on the sea surface, using the screen-plane and WIG (Wing-in-Ground) effect, with the maximum speed of about 250 knots, and finally the variant "Spalato" as the first phase in investigations, which can glide on the sea …surface with the speed up to 80 knots. This vessel is an original concept based on the optimum use of both media (air, water) using aerodynamic effects, load carrying capability and hydrodynamic lift for flying and stabilization of vessels, as well as for decreasing total resistance. Show more

Keywords: super-high speed vessel, flying-landing maneuver, soil effect, load carrying capability, profile rising, total resistance

Citation: International Shipbuilding Progress, vol. 49, no. 2, pp. 127-153, 2002