| With the global warming,the sea ice on the Arctic channel is melting.Arctic areas appear ice-free period in summer,that provides a golden opportunity for the navigation of the vessels,and there have been a number of merchant vessels successfully getting through the Arctic channel.As the Arctic channel is of great economic benefits,quickly get the major shipping companies close attention.However,due to the special environment under the polar conditions,there is much crushed ice into the ship’s maritime piping system on the channel.The sea ice in the pipeline continue to accumulate the formation of clogging,leading to the ship water cooling system paralyzed,and the cooling water temperature rises rapidly beyond its normal operating temperature range,resulting in ship equipment can not work properly,and ultimately the entire ship power system can not run.Therefore,it is necessary to carry out the phase field simulation of the solidification process of seawater ice crystals in the polar environment and the analysis of the flow characteristics of the sea water ice two-phase flow in the pipeline.Based on the Ginzburg-Landau theory,the Wheeler model was used as the phase field model of seawater ice crystals.In order to obtain the dendritic morphology of seawater ice crystals with secondary or higher seawater more accurately,anisotropy and thermal disturbance are introduced into phase field model.The control equations(phase field,temperature field,concentration field and velocity field control equation)in the phase field model are discretized using finite difference method which is easy to program and solve,and the results are analyzed by Tecplot.The results show that under the pure diffusion,the dendritic morphology exhibits a strict six-symmetry,and the angle between the adjacent six primary arms is 60°,and the angle between the secondary arm and its primary arm,which is grown on the primary arm,is also 60 °,at the same time the primary arm and secondary arm of the root appeared a significant necking phenomenon,the phase field simulation eventually obtained snow-like ice crystal.The solute distribution obtained on this basis is very similar to the dendritic morphology,and a large amount of solute enrichment occurs at the solid-liquid interface;with the introduction of forced convection,the six-symmetrical structure of dendrites has been seriously damaged,the growth rate of upstream dendrites which can not grow secondary arm is obviously smaller than that of downstream side,and primary arm and secondary arm of downstream side are more developed.The growth rate of the tip of the dendrites and the segregation ratio of the solute increase with the increase of the flow rate,the disturbance intensity and the degree of subcooling,When these parameters are large,the pipeline is prone to ice blocking,causing the ship to fail and the value of heterosexuality has little effect on the growth rate of dendrites.When the anisotropy and disturbance intensity are too large,the disorder will occur,leading to the distortion of sea ice crystals.Under the periodic force field,the flow characteristics and heat transfer characteristics of the frozen water pipeline were analyzed and numerically simulated.The simulation results show that with the introduction of disturbance,the heat transfer coefficient of seawater ice and pipeline increases rapidly,and the disturbance intensity is further increased.But the accumulation area of ice crystals in the central part of the pipeline is decreasing and the heat transfer coefficient is slightly increased more fully.The results are in good agreement with the results of the fourth chapter on the effect of disturbance intensity on the growth of ice crystals,which verifies the reliability of the simulation results both macroscopically and microscopically. |
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