Estimation of the Spectrum of Non-Linear Ship Rolling:The Functional Series Approach.

摘要

The objective of the present work was to investigate the applicability of the functional series model to nonlinear ship rolling, under the assumption that the usual single-degree-of-freedom rolling equation holds. Particular emphasis was given to the development of means of estimating the spectrum of nonlinear roll. In applying the functional series to roll it was found necessary to approximate the usual quadratic damping representation by a cubic. Given this, the application was reasonably straightforward. Expressions were developed for the spectrum of roll in the form of a series carried through to terms of fifth degree. A trial evaluation of the spectrum of a previously simulated case of nonlinear rolling was made under the assumption that terms of fifth degree were negligible. The results appeared reasonable for moderate rolling at least. It appears that the functional series approach, while not the only approach to nonlinear rolling, might be developed into a practical alternative. (Author)