Study On The Mechanism Of Resistance Increase Of Ships In Marginal Ice Zone Under The Coupling Effect Of Ice Floe And Wave

The polar periglacial area is located at the junction of the ice-covered area and the open waters,which is the only place for ships sailing in the polar region.In recent decades,with the significant warming of the Arctic region,the scope of the periglacial area is also expanding.Ships sailing in the periglacial area will be affected by the coupling of wind-wave-current and sea ice even when the icebreaker is piloted.Its resistance performance is different from that of sailing in the ice floe area alone.At present,scholars at home and abroad have carried out a lot of research work on the navigation performance of ships sailing in crushed ice and smooth ice channel,but there are few studies on the ship-crushed ice-wave coupling in the periglacial area,and many key mechanisms and laws have not yet been revealed.In this paper,aiming at the above-mentioned navigation problems of ships in the periglacial area,numerical simulation research is carried out based on the finite element method,and combined with the unfrozen paraffin model ice test,the resistance increasing mechanism of ships sailing in the periglacial area under the action of broken ice-wave coupling is studied.Firstly,the research status of the ice resistance of ship-ice interaction and the interaction between floating ice and waves in periglacial area is analyzed,and the advantages and disadvantages of each research method are summarized.The applicability of the StructuredArbitrary Lagrangian Eulerian(S-ALE)fluid-solid coupling method is verified by the examples of wedge-shaped water entry and single piece of sea ice floating in still water.Then,the ship-crushed ice-water interaction was studied.S-ALE fluid-solid coupling method and submerged penalty function contact algorithm are used to simulate the process of ship-ice-water interaction,and a correction method for calculating fluid resistance by using this numerical simulation method is proposed.Typical phenomena of ship-ice interaction,such as overturning,stacking of crushed ice,lateral sliding along ship’s side and gathering of crushed ice wake,are observed.By analyzing the process of ship-ice-water interaction in frequency domain and time domain,the law of resistance increasing characteristics of total resistance of ice-water mixing and various resistance components with the change of speed and crushed ice density is summarized as follows:The resistance components of the total resistance change with the model speed and the density of crushed ice,which leads to different proportion of resistance increment.The growth rate of ice-water mixing total resistance and crushed ice resistance shows the trend of first fast,then slow and then fast with the increase of hull speed.The total resistance and crushed ice resistance increase with the increase of crushed ice density.Then,the interaction between crushed ice and waves is studied.The numerical wavemaking method based on finite element method is emphasized,and the dynamic boundary condition numerical wave-making method is combined with the numerical simulation method of ship-ice-water interaction to simulate the interaction process between crushed ice and waves.The longitudinal and heave motion responses of crushed ice groups under the action of waves are analyzed,and the motion laws are summarized as follows:The longitudinal motion of the broken ice group in waves shows two motion states: irregular motion in the short-wave range and regular motion in the long-wave range.There is no regular difference in the longitudinal motion response parameters of crushed ice of different sizes.With the increase of wavelength,the average longitudinal drift velocity of ice floes increases rapidly at first,then decreases gradually and tends to zero.The heave response speed and displacement amplitude of ice floes oscillate violently in the short-wave range,which can’t be measured.In the long-wave range,it increases rapidly with the increase of wavelength,and then the displacement amplitude quickly exceeds the wave height and then decreases slowly,but it continues to exceed the wave height.With the increase of wavelength,the heave response period of ice floes is slightly larger than the wave period at first,and then approximately overlaps with the wave period.Finally,the mechanism of ship-crushed ice-wave coupling resistance increase is studied.The whole process of ice load unloading under wave action was observed and described.The total coupling resistance of ships sailing in the periglacial area and various resistance components were quantitatively analyzed.The laws of wave resistance increase,broken ice resistance increase and ship-ice-wave coupling resistance increase were summarized as follows:The superposition of the change of crushed ice resistance and wave resistance causes the change of crushed ice-wave coupling resistance,and the wave resistance and crushed ice resistance in the total resistance collide with each other.The total resistance increase of shipcrushed ice-wave coupling increases with the increase of speed,wave height and crushed ice density,but there is no obvious regularity with the change of wavelength.Wave one timing,With the increase of wavelength,the total resistance coupling resistance approximately shows the trend of decreasing at first and then increasing,and under the condition of λ/L =1 wavelength,the ice-wave coupling plays an important role in reducing the resistance.When the wavelength is constant,the change of total resistance with the increase of wave height is mostly the effect of coupling resistance reduction,and the coupling resistance decreases faster with the increase of wave height.The faster the speed,the more obvious the effect of coupling drag reduction.