Ice Resistance Prediction And Parameters Sensitivity Study For Polar Geophysical Prospecting Vessel

With the reduction of sea ice extent and ice thickness in the arctic channel in summer and autumn,the use value of the channel is gradually increasing.Under the circumstance of opening up the arctic channel,its resource exploration is imminent,and polar geophysical prospecting vessels(GPV)also emerges as the times require.Due to the particularity operations of the polar geophysical surveying,it is required to service operate between the polar seas and other open seas every year.The operating window period is usually summer and autumn,but it is highly vulnerable to level ice conditions at the end of the operation window period or during the return voyage.The polar GPV still need to have a certain ability of ice breaking.The pack ice and level ice conditions in the polar region will have a great impact on the ship's ice resistance,while the resistance will affect the towing capacity of the polar GPV,which plays a decisive role in the economy and efficiency of the GPV.Therefore,it is of great engineering significance to carry out the ice resistance prediction and parameters sensitivity research of polar GPV in the pack ice and level ice environment.It is the core issue in the design and optimization of polar GPV.In this paper,the ice materials' s constitutive model of the elastic fracture failure model is verified by the pressure-area curve.Based on Voronoi diagram,parametric modeling of pack ice with random distribution and irregular geometry is carried out.Global optimization of MCD probability distribution of pack ice is carried out by using genetic algorithm.Finally,using the fluid-structure interaction technique of the nonlinear finite element software LSDyna,the numerical simulation of the ice resistance prediction and related parameters sensitivity of the GPV sailing in the pack ice and level ice environment was carried out.The relevant empirical formulas are compared and analyzed to provide reference for the study of GPV' ice resistance.The specific research content of this paper is as follows:1.According to the specification,the related theory of pressure-area curve is combed,and the basic principle of LS-Dyna in nonlinear structure analysis is introduced.Based on the ice material of elastic fracture failure model with plastic strain failure,the simulation of steel plate extruding ball head ice body is designed and developed.The numerical numerical simulation of the ball head ice body analyzes the compression mode of the ice body,the pressure distribution characteristics of the contact surface,the mutual transformation process between HPZs and LPZs.Finally,the P-A curve which are in good agreement with the codes and relevant experimental data is obtained,which verifies the reliability of the elastic fracture failure model to simulate the ice material,and lays a foundation for the prediction of ice resistance of GPV in the pack ice and level ice environment.2.Voronoi diagram is used to parameterize the brash ice with random distribution and irregular geometry.Referring to the probability distribution law of the brash ice's MCD in real ice zone,the model of brash ice is optimized globally based on genetic algorithm,which is close to the natural environment.Using LS-Dyna fluid-structure interactions(FSI)technology,the numerical simulation of the cruise of GPV in the brash ice before and after optimization was carried out,and the effects of scale effect and MCD probability distribution on brash ice resistance were analyzed.The study found that compared with large-scale brash ice,small-scale brash ice have higher frequency impact loads,larger load pulse width and higher frictional resistance ratios,which significantly enhance the brash ice resistance.The brash ice resistance calculated based on the model generated directly by the Voronoi diagram is too conservative.Optimizing the MCD probability distribution can improve the numerical prediction accuracy of the brash ice resistance.3.Based on the spatial distribution of sea ice observed in China's Fifth Arctic Expedition,considerring the influence of sensitivity parameters(brash ice thickness,brash ice concentration and ship velocity)on the ice resistance of GPV sailing in brash ice zone.LSDyna FSI technology is used to carry out numerical simulation research on the ice resistance of GPV sailing in the brash ice zone.The professional fluid calculation software STARCCM+ is used to calculate the open water resistance of GPV at different velocity.The variation trend of brash ice resistance and the proportion of brash ice resistance in total resistance under the influence of various sensitity parameters are analyzed.The study found that the brash ice resistance increases linearly with the increase of brash ice concentration,ice thickness and ship velocity.Except for case of 20% concentration,the brash ice resistance under the remaining cases can account for more than 65% of the total resistance.4.Considering the influence of sensitivity parameters(ship velocity and level ice thickness)on the icebreaking resistance of GPV,the LS-Dyna FSI technique is used to carry out numerical simulation research on the ice resistance of GPV sailing in level ice.The ice damage mode and the ice resistance change under the influence of various sensitivity parameters during the icebreaking process of the GPV were compared,and the ice breaking resistence of the numerical simulation results was compared with the calculated value of the Lindqvist empirical formula.The study found that the icebreaking resistance of GPV increased linearly with the increase of ship velocity and ice thickness.Under different ship velocity and level ice thickness conditions,the icebreaking resistance and Lindqvist empirical value error is in the range of-7.5%~13.1% and-10.8%~19.4% respectively.The FSI method has high reliability for the prediction of icebreaking resistance.