The disturbances of the life raft leeway induced by the fluctuations of wind direction in the life raft coordinate system

Abstract

The paper presents the results of investigations on the life raft leeway induced by the fluctuations of wind direction. The surface current is one of the main factors determining the life raft leeway, but the recently conducted research confirmed that there are also other elements influencing the perturbations of leeway direction. The field experiments showed diversion of the life raft leeway from the downwind direction. This diversion can be explained by the existing cross wind component. The wind tunnel tests allowed to determine the aerodynamic coefficients in the fluid-state control system. On the basis of the test results the expression for the wind pressure force has been formulated. The mean deviation and median of probability distribution of the leeway diversions from the downwind direction has been determined on the basis of investigations conducted at sea. The models for the life raft velocity dependent on wind velocity, developed for the life raft with drogue and without drogue, are presented in the paper.