International Shipbuilding Progress

The paper looks at various forms for the roll damping moment of ships and introduces two techniques to identify the parameters of the various models together with a methodology for their evaluation. The emphasis in the paper is on the possibility of using complete portions of roll decay curvf1s rather than decrement curves derived from the peak values of the decay curve. Also the appropriateness of including angle dependent components in the form of the roll damping moment is discussed.

The wave interaction of a floating sphere with two vertical walls is discussed. Graphs of the frequency domain and equivalent time domain added mass, damping, Froude-Krylov and diffraction forces, and Response Amplitude Operators (RAO) are presented. The linearized frequency domain velocity potentials are constructed by a multipole expansion used in conjunction with the method of images. The discrete Fourier Transform converts frequency data to Impulse Response Functions (IRF). Peaks in the IRF envelope curve indicate the effect of outlying images, which for practical cases are separated in time. A technique for identifying wall reflection effects from measurements in a finite basin is described.

This paper suggests a simplified mathematical model for an onboard manoeuvring simulator. Concerning the human factors affecting manoeuvring situations, it seems clearly evident that at least two factors affect the skill requirements of master mariners: familiarity and recency of experience with ship type. So far, the possibility of having on board a real time compact manoeuvring onboard simulator would give to ship officers a chance for self-training in a real trim condition in order to quickly achieve the needed familiarity and recency of experience. Lengthy scenario, such as a ship negotiating a long buoyed channel, could be run quickly on a fast time computer in the onboard simulator, enabling the master to anticipate his manoeuvring decision result.

The mathematical ship's model used in this report is the simple first order Nomoto's model.

The block diagrams and the further research efforts presented in this report are the research guidelines of the Istituto Universitario Navale at Naples, Italy, for designing a shipborn manoeuvring simulator for ship control.