A New Coordinate System and the Equations Describing Manoeuvring Motion of a Ship in Waves

TLDR

The paper aims to derive a combined equation of motion that captures horizontal manoeuvring, lateral rolling, and vertical seakeeping dynamics of a ship. The authors introduce a Horizontal Body Axes coordinate system, evaluate Froude‑Krylov and hydrodynamic forces within it, and perform time‑domain simulations of turning and zig‑zag trials in waves. The study concludes that the Horizontal Body Axes system can effectively describe ship motions across all six degrees of freedom.

Abstract

The purpose of this paper is to find an equation of motion in a reasonable combination describing the manoeuvring motions in horizontal plane, rolling motion in lateral plane and seakeeping motion in vertical plane. The reasonable combination here is to find such a coordinates system as using the formulae with respect to the hydrodynamic forces which have been developed in field of manoeuvrability, stability and seakeeping. A new coordinate system called Horizontal Body Axes is presented for describing the equations of manoeuvring motion of a ship in waves. Froude-Krylov forces and Hydrodynamic forces on a ship are evaluated with respect to Horizontal Body Axes. The Time domain simulations are carried out for turning and zig-zag trial of a ship in waves. Finally, it is concluded that this new coordinate system would be considered to be available for describing ship motions having six degrees of freedom.