INVESTIGATION INTO THE PHYSICS OF SHIP CAPSIZING BY COMBINED CAPTIVE AND FREE-RUNNING MODEL TESTS

Abstract

Ship capsizing in heavy seas is a problem that still awaits a solution. A comprehensive study of the physics of the capsize phenomenon, focused on the behavior of small fishing boats in extreme waves, has been conducted by the National Research Council of Canada. The paper presents a philosophy of an original concept of experimental investigation into the mechanism of ship capsizing, involving a specially designed combination of free and captive model tests. Also outlined are the developed experimental technique and the test program. The experimental data obtained are unique. The detailed analysis of some of the free model runs provides an insight into ship kinematics in quartering and beam waves, while the examination of the captive tests identifies the composition of the exciting hydrodynamic forces and moments. The majority of the paper is dedicated to analysis of the mechanism of ship capsizing in quartering waves. Various types of capsize and their causes are presented. Special attention is paid to the influence of bulwark submergence. The hydrodynamic phenomenon and the subsequent couplings and heeling moments created by bulwark submergence are discussed. Some other factors influencing ship capsizing are also considered.