Accession Number : AD0647178

Title :   LOW-SPEED CONTROLLABILITY OF SHIPS IN WIND,

Corporate Author : STEVENS INST OF TECH HOBOKEN N J DAVIDSON LAB

Personal Author(s) : Eda,Haruzo

Report Date : OCT 1966

Pagination or Media Count : 63

Abstract : Aerodynamic and hydrodynamic data for the MARINER-Class vessel were used to formulate a mathematical model representing the dynamic behavior of ships in wind. A digital computer was used to solve the eigenvalues of the system. Perturbation equations were linearized, with respect to equilibrium conditions, from non-linear equations of motion. In addition, ship-trajectory in certain wind conditions was examined by means of numerical solutions of the non-linear equations of motion. Results indicate that the ship in bow wind tends, even without an autopilot system, to maintain its original course - with perturbation in yaw inducing yaw oscillations, the convergence of which depends upon the magnitude of relative wind velocity. It is shown that beam wind creates greater difficulties, although the use of an adequate autopilot increases the region of stability in wind of certain velocities (excepting in some conditions of relatively strong beam wind). An increase in rudder size is shown to improve controllability in wind, significantly. Computations with and without the assumption of constant longitudinal speed indicate that the effect of surge motion on yaw and sway responses in wind is important, especially in beam wind. (Author)

Descriptors :   (*SHIPS, CONTROL), (*WIND, SHIPS), STABILITY, EQUATIONS OF MOTION, MANEUVERABILITY, GUST LOADS, FORCE(MECHANICS), STEERING, YAW, VELOCITY

Subject Categories : Marine Engineering

Distribution Statement : APPROVED FOR PUBLIC RELEASE