International Shipbuilding Progress

A perturbational process is applied to the non-linear rolling of a ship in a sea described by the power spectral density of its waveslope; this produces a formula which is simple to apply. The results indicate that the roll power spectral density is “harder” than that predicted from linear theory which appears to be in keeping with measured data previously published.

Graphical and analytical methods have been previously provided for the hull surface generation and calculation of the main geometric particulars of the SSPA cargo liner series [1,2]1 ¹

Numbers in brackets refer to References listed at the end of this paper.

This paper presents the results of the regression analyses performed on the resistance and propulsive coefficients data of the SSPA cargo liner series, which aimed at developing analytical expressions not involving unvalid assumptions and provide the necessary corrections to account for variations in the LCB position from the standard adopted. These regression equations are subsequently used to form a computer program for the calculation of the resistance and propulsive coefficients of any intermediate form within the range of the series, and are compatible with the generated hull forms provided from earlier analysis.

The improvement in performance which can be obtained by application of ducted propellers on bulk carriers and tankers depends very much on, the afterbody-nozzle configuration. Investigations carried out so far on these applications are mostly restricted to isolated cases.

In this paper, based on systematic tests performed in the Depressurized Towing Tank of the Netherlands Ship Model Basin, information is given about the influence of nozzle length, nozzle shape, propeller diameter, hull-nozzle clearance and about the influence of adaptation of the nozzle to the wake flow on the performance of large ships.

A great deal of effort has been devoted in recent years to study of the deformation of the wake from propeller blades. Relationships between loading, vortex rollup, contraction, and pitch variation have been studied. This paper discusses analytical and experimental developments, and emphasizes the effects on design and performance of high speed high thrust subcavitating propellers.