| In recent years,with the development of Arctic waterways,the potential exploitation of Arctic resources,and the vigorous development of scientific investigations and developments in polar regions,there has been an urgent need for ships’ icebreaking capabilities and navigation capabilities in severe ice conditions.In addition to optimizing the shape of the icebreaker hull,adding an auxiliary icebreaking system is also one of the effective means to improve the icebreaking ability of the icebreaker.The air bubble assisted ice breaking and clearing system is one of the effective means of assisting icebreaking by polar icebreakers.It is necessary and important for the in-depth study of its working mechanism.However,although the bubble assisted ice breaking system has been applied,for various reasons,related research on bubble assisted ice breaking However,it is very rare,which makes the interaction mechanism between the air bubble assisted ice breaking and clearing system and sea ice not fully understood.Aiming at the problem of the air bubble assisted ice breaking and clearing system and the mechanism of drag reduction,this paper uses a combination of model tests and numerical calculations to study the bubble-ship-breaking ice interaction phenomenon and drag characteristics of the polar icebreaker equipped with the air bubble assisted ice breaking and clearing system.In the model test part of this paper,the non-frozen model ice made of polypropylene is used to study the resistance characteristics of air bubble assisted ice breaking and clearing system in the towing tank.The Xuelong 2 polar scientific research icebreaker is used as the prototype of the ship model.The phenomenon of interaction with crushed ice,as well as the change law of resistance characteristics under different concentrations of crushed ice,different ship model speeds and different ventilation parameters are carried out.The results show that the air-water mixed flow and bubbles produced by the air bubble assisted ice breaking and clearing system severely disturb the movement of the broken ice around the hull,and have a beneficial effect on the formation of the broken ice channel.At the same time,it is found that the drag reduction effect of the system is mainly affected by the three factors of aeration,the density of broken ice,and the speed of the ship,and even under the same ventilation conditions,the influence of the density of broken ice and the speed on the drag reduction rate is still significant.In this paper,the numerical simulation of the icebreaker’s navigation process in the icebreaking area with air bubble assisted ice breaking and clearing system is carried out based on the CFD-DEM coupling method,and the ship-broken ice-water coupling frame is built in the fluid dynamics software STAR-CCM+.The numerical calculation method is briefly introduced,including the control equation,turbulence model,crushed ice particle contact theory,particle model and the choice of emitter.Then the numerical calculation results and the ship model test results are compared and analyzed.The simulation of the physical phenomena of bubble motion characteristics and the interaction between the hull and the broken ice shows good agreement with the test.At the same time,the ship ice resistance is also consistent with the ship model test.There is good consistency in resistance trend and value,and the dimensionless error is about11%.The flow field around the hull,the movement and distribution of broken ice,and ice resistance characteristics of icebreakers with or without air bubble assisted ice breaking and clearing system,different air hole arrangements and ventilation rates when sailing in the ice breaking area are further compared.The results show that the air hole at the bow position and the air hole at the side of the ship have different degrees of contribution to the reduction of the overall ice breaking resistance,of which the ice breaking resistance on the bow is the main part,so the ventilation of the bow air hole has a greater impact on the drag reduction rate. |
