Research On Forecasting Method Of Polar Ships Ice Load Accounting For The Sea Ice Uncertainty

Nowadays,with the increasing geostrategic importance of the two poles,the international community is paying more and more attention to the polar resources and the Arctic waterways.As a result,the research on polar ships has received more attention.During the design phase of polar ships,accurate prediction of the ice load on the hull is very essential.However,the focus of current research on ice load is mainly placed on deterministic analysis,and the randomness of sea ice parameters and the random characteristics of ice load are not considered.In this thesis,the ice load forecasting method is studied accounting for sea ice uncertainty,and the random characteristics of ice load on the continuous ice breaking process of polar ship are summarized.The contents of the work carried out in this thesis are as follows:1.Improve the existing method for predicting the ice load on polar ships.A torque balance method is adopted to calculate the bollard pull.Based on experimental results,corrections have been made to an existing formula for calculating the ice crushing resistance during stern ice-breaking.Considerate attention has been given to the dynamic loading effect of the hull on the sea ice,and a more accurate sea ice bending failure criterion is introduced.In addition,the possible crushing damage of sea ice is also taken into account,and the sea ice crushing failure criteria is established so as to establish a more reasonable ship-ice interaction model.2.The numerical calculation method of ice load of polar ship is validated.A computer program based on the established method for predicting the ice load on polar ship is developed.The ice load on the polar ship in a continuous ice breaking process is predicted.Comparison of the results with the ones obtained by a nonlinear finite element method and also with those from ice load model tests shows that the method devised in this thesis is fairly accurate.3.The method for predicting the ice load on polar ships accounting for sea ice uncertainty and the random characteristics of ice load are studied.Random ice load is calculated accounting for the uncertainties of sea ice thickness and strength and also the correlation between them.Based on the results obtained for the ice load,a method for obtaining the function of random ice force is established.The characteristics of the extreme values of random ice load are analyzed.A Weibull distribution fit is made for the ice load extremities.Analysis of the pattern of the distribution parameters indicates that the distribution parameter and ice thickness follows a cubic function.Finally,the probability density function of the ice load extrema is obtained by means of analysis.