Preliminary Forecast For The Maneuverability Of Icebreaker In Level Ice

As the global warming, polar ice melting and ice thickness decreasing, development and competition for the arctic resources is escalating. Icebreaker as a special purpose ships in ice has been used in some important tasks, such as waterway opening, polar rescue and material supply.Therefore, more and more emphasis is attached on the research of icebreaker. It is an initial stage of the research on motion performance oh icebreaker in our country, so there are many problems to be solved. The main purpose of this article is to establish maneuverability forecast model of icebreaker through the study of the three degree-of-freedom rigid body equations of icebreaker in level ice, and to form a preliminary theory for the maneuverability forecast of icebreaker in level ice and a simulation prediction software. So, there are theoretical basis and technical support for forecast maneuverability of icebreaker in future.In this paper, based on summing up the physical and mechanical properties of sea ice and analyzing the form of interaction between sea ice and icebreaker and continuous breaking process,a theoretical method is established for calculating the ice resistance. The experience formula of ice resistance is summed up including Lindqvist, Riska and other earlier empirical formula. A polar vessel is simulated in different ice thickness and different speed based on the finite element software LS-DYNA. The results of simulation and experience formula are compared to verify the accuracy of theoretical method.Then, the three degree-of-freedom rigid body equations of icebreaker in level ice is established though the analyzing movement of icebreaker and simplify by reasonable. According to the MMG theory, ice resistance is thought as an external force on the icebreaker. So the external force is divided into hydrodynamic force acting on hulls, control power (force of propeller and rudder) and environment disturbing force (mainly ice resistance). The calculation model of hydrodynamic force acting on hulls, control power and environment disturbing force is expounded in both open water condition and level ice condition.Afterwards, the hydrodynamic derivatives of icebreaker in level ice are analysis in theoretical and the calculation model is given. STAR-CCM+ and LS-DYNA is used respectively to simulate a polar vessel's motion in open water condition and level ice condition. The hydrodynamic derivatives in both open water condition and level ice condition are calculated according to the non-linear curve fitting on the transverse force and transverse moment curves of icebreaker motions. So, the hydrodynamic force acting on hulls is perfected and influence of level ice about hydrodynamic derivatives is analyzed.Finally, with the help of the MATLAB programming language and the fourth-order Runge-Kutta method for solving three degree-of-freedom rigid body equations of icebreaker in level ice, a numerical preliminary simulation computer program is compiled. With mixed programming and VB language, a simulation platform is compiled to forecast the maneuverability of icebreaker in both open water condition and level ice condition. Then,the result can be output into a formative calculation report. A good agreement is achieved through comparing the numerical simulation of icebreaker AHTS/IB Tor Viking ? in level ice with the ship performance data from the ice trails. So the method which forecasts the maneuverability of icebreaker in level ice and the simulation platform has good applicability.