DETERMINISTIC ANALYSIS OF EXTREME ROLL MOTIONS AND SUBSEQUENT EVALUATION OF CAPSIZING RISK

摘要

Encountering a freak wave remains one of the most horrible visions for a ship master. Until now the mechanisms which underlie large rolling and subsequent capsizing due to a rogue wave are only partly disclosed. In the framework of the German research project ROLL-S which is funded by the German Federal Ministry of Research and Education (BMBF) nine partners are cooperating on the investigation of large rolling and capsizing mechanisms covering fields like numerical analysis and simulation, validation, and evaluation of capsizing risk. The project pan presented here deals with the validation of numerical tools for the analysis of large rolling and capsizing. The main goal is the implementation of a sophisticated capsizing test procedure. For providing useful data for the analysis of the capsizing process as well as for the validation of numerical methods, exact correlation of wave excitation and ship rolling is indispensable. All wave trains are tailored for the specific purpose of each capsizing test and generated in the model tank. Unusual wave trains like regular waves followed by a freak wave and special wave groups within a defined random sea as well as realistic wave scenarios have been generated. The parameters of the model seas are systematically varied to investigate the ship model response with regard to metacentric height, model velocity, and course angle for different ship types. The wave elevation at the position of the ship model in time and space is calculated (and controlled by registrations during model tests) in order to relate wave excitation to the resulting roll motion.