Research On Efficient Simulation Method Of Ship Continuous-mode Ice Breaking Performance

Continuous-mode ice breaking is the most typical ice breaking mode for medium and high ice class polar ships.Excellent ice breaking navigation performance is the key to ensure the safe operation of ships in polar regions.At present,the prediction of continuous-mode ice breaking navigation performance mainly depends on the conversion from the ice tank model test results to full-scall results.The construction of large-scale ice tank in China is in the initial stage,which can not effectively support the prediction of continuous-mode ice breaking navigation performance and the development of polar ships.It is of great practical significance to develop accurate and efficient numerical prediction methods of continuous-mode ice breaking navigation performance.In order to support the research and development of polar ship engineering,this paper innovatively proposes a numerical model theory of ship-ice interaction based on the preset square ice grid technology,systematically develops the efficient simulation methods and programs of typical navigation performance such as continuous-mode ice breaking resistance,ice breaking ability and turning in level ice,and carries out systematic numerical simulation and experimental verification analysis.Based on the above research,the ship’s high-efficiency and high-precision engineering prediction of continuous-mode ice breaking navigation performance is realized.Firstly,based on the mechanism of continuous-mode ice breaking and the idea of finite element method,an efficient numerical model of ship-ice interaction is established.Based on the numerical model,the continuous-mode ice breaking process is divided into a cyclic iterative process of contact-crushing-multiple failure.The Newmark method is used to dynamically solve the six degree of freedom motion differential equation of the ship in time domain,and the numerical simulation method of continuous-mode ice breaking resistance considering the coupling of motion and force is developed,which achieve the decoupling calculation of ship motion and ice resistance.The effectiveness and efficiency of the numerical simulation method are verified by the numerical simulation of two polar ships.The numerical simulation results are in good agreement with the results derived from model test.Secondly,based on the observation of model and full-scall measurements,the generation of transverse ice resistance is approximated as a first-order Gauss-Markov process,and the numerical simulation method of the transverse ice resistance is developed by use the statistical uncertainty theory.The time history of the transverse ice resistance obtained by the numerical simulation is in good agreement with the model test results.The influence of the transverse ice resistance on the longitudinal ice resistance is further analyzed,and the numerical simulation theory of continuous ice breaking resistance is improved.Thirdly,based on the theory of continuous-mode ice breaking and propeller net thrust estimation formula,two ice breaking capacity evaluation methods are proposed: static method and dynamic method.The ice breaking capacity curves obtained from different evaluation methods are compared with the model test results,which verifies the effectiveness and engineering applicability of the numerical evaluation methods,and provides an effective tool for engineering evaluation of ice breaking capacity.Fourthly,based on the ship-ice interaction numerical model,a three degree of freedom numerical simulation method of turning in level ice is established in the horizontal plane by using the MMG separation modeling idea,which takes into account the coupling of ship motion and ice resistance.The maximum turning diameter,turning trajectory and turning ice breaking channel are obtained by numerical simulation,which are in good agreement with the full-scale test of icebreaker Tor Viking II,the effectiveness of the numerical simulation method is verified.Fifthly,according to the operating characteristics of the double acting icebreaker propeller,the test technology of propeller performance in ice blocking environment is established in the cavitation tunnel laboratory,and the hydrodynamic performance tests of propeller model in ahead and astern state under uniform flow and ice blocking environment are carried out.The flow field details of ice-propeller interaction in ice blocking environment are analyzed by CFD technology.The findings provide support for mastering ice-propeller interaction mechanism and polar ship propeller performance correction.The efficient simulation methods of continuous ice breaking navigation performance developed in this paper can be used to predict the navigation performance of polar ships in the preliminary design stage,further guide the optimal design of hull form,and strongly support the research and development of polar ship engineering in China.