Numerical Simulation Of Sea Ice Dynamics With Modified Discrete Element Method In The Bohai Sea

The ice cover plays an important role for global climate in polar regions, and also brings a series of engineering problems in the sub-polars. To solve the relative problems above at various scales, the numerical simulation of sea ice dynamics have been investigated for more than several decades. To improve the computational precision and efficiency of sea ice drifting and rheology, some efforts have been carried out from two aspects, effective numerical methods and reasonable constitutive models.For the numerical model of sea ice dynamics, there are mainly four kind methods applied widely, which are finite different method (FDM), particle-in-cell (PIC), smoothed particle hydrodynamics (SPH) and discrete element model (DEM). For the constitutive models of sea ice dynamics, the exiting constitutive models can be divided briefly into three groups, e.g. elastic-plastic (EP), viscous- plastic (VP) and its modifications, and viscous-elastic-plastic (VEP) contact force model in DEM. In both of numerical models and constitutive laws above, the discrete element model is quite different with others, since it treats the ice cover as discrete materials, while all of others, either FDM, PIC and SPH in numerical method or VP, EP models in constitutive law are based on continuum theory.In the field observations and satellite images, it was shown that the sea ice performs as granular materials, and level ice, rafted/ridged ice and ice leads are mixed randomly. To model the dynamic characteristics of sea ice cover in discrete state, the discrete element model (DEM)) has been applied more and more recently. In the previous DEM simulations, the ice cover is described as rigid blocks with constant size and thickness. Under meso-large scales, the messages of ice blocks (i.g. ice thickness, position, velocity, size and shape, etc.) can not be determined exactly. Therefore, a modified DEM was established in this present study. In this modified DEM, the interaction among ice particle is determined with the viscous-elastic-plastic contact model. And the most novel portion in this method is the plastic deformation, which can consider the ice rafting and ridging, and affect the thickness of ice particles. In addition, considering of the influences of sea ice thermodynamic factors on ice conditions, a sea ice thermodynamic-dynamic model was established based on the DEM model for sea ice dynamics.With this modified DEM, the ice ridging in a rectangular region is simulated, and the results are compared with the analytical solution. The ice drifting process in a vortex wind field is also modeled, and its computational precision is compared with PIC model. Moreover, the sea ice dynamics of Bohai Sea is also simulated in 48 hours. The simulation results show that the DEM method has high precision, could describe sea-ice edge accurately.It could be used in the Bohai sea ice numerical simulation preliminary. However, this method' efficiency is low, need further improvement.