Dynamic ship maneuvering model in brash ice

• Main Author: Romu, Tuomas
• Other Authors: Suojanen, Reko-Antti, Insinööritieteiden korkeakoulu, School of Engineering, Sovelletun mekaniikan laitos, Kujala, Pentti, Aalto-yliopisto, Aalto University
• Format: Master Thesis
• Language: Finnish
• Published: 2013
• Subjects: simulator; brash ice; maneuvering; simulaattori; rännijää; sohjojää; ohjailu; Arctic; Jota; Icebreaker
• Online Access: https://aaltodoc.aalto.fi/handle/123456789/100923

The aim of this thesis was to develop a calculation model that can be used to simulate the movement and manoeuvring of a ship in brash ice. The intended use of the calculation model is an operative manoeuvring simulator that can be used for training purposes. After reviewing previous research and existing analytical and numerical methods for calculating forces resulting from brash ice, an analytical model derived from soil mechanics was chosen for further development. Previously, a similar model had been used for predicting the ice resistance of a ship in a brash ice channel. In the calculation model, the hull geometry of the vessel was described at the waterline by dividing it into segments. Ice forces were calculated at each waterline segment from local hull geometry described by the surface normal vector, motions of the vessel and brash ice properties. A three-degree-of-freedom manoeuvring model was used to determine the accelerations and velocities of the vessel. The calculation model was verified by comparing simulated brash ice resistances and turning circle diameters of an icebreaker and two LNG carriers with model tests conducted by Aker Arctic. In addition, a theoretical study was conducted using the product tanker Uikku. For brash ice resistance, results from the simulations were of the same magnitude with the model tests. However, simulated turning circle diameters were 2.5-3 times as large as those measured in model tests. This is likely due to the simplifications made in the calculation model, especially concerning the hull geometry and handling of the brash ice around the vessel. However, based on the theoretical study it was deemed that with some improvements the calculation model would be suitable for an operative manoeuvring simulator. Työn tavoitteena oli kehittää laskentamalli, jota voidaan käyttää aluksen liiketilan ja ohjailun simulointiin paksussa jääsohjossa. Laskentamalli on tarkoitettu käytettäväksi operatiivisessa ohjailusimulaattorissa, jota voidaan käyttää koulutustarkoituksiin. ...