基于Voronoi切割算法的碎冰区构造及离散元分析

离散元方法广泛应用于海冰，特别是碎冰区的动力过程及其对海洋结构作用过程的数值模拟。为构造碎冰区中的冰块几何特性，基于二维Voronoi图方法对计算域进行随机切割以生成碎冰区中冰块的几何形态，并采用球体单元对每个碎冰块单元进行填充，从而确定碎冰区的初始分布场。在采用Voronoi图进行碎冰区构造时，可对冰块尺寸、几何形态和密集度等海冰参数进行设定。为确定冰块的不同几何规则度，综合采用排斥法和扰动法以定量地控制碎冰块几何形态从完全随机分布到规则分布的连续变换。为分析不同几何规则度下碎冰块的几何特性概率分布规律，对计算域内冰块的面积和边数等参数进行统计分析，从而可更合理地参数化控制初始冰场中碎冰块的几何特性。在此基础上，本文基于粘接-破碎的球体离散元方法对不同冰况下锥体结构的冰荷载进行了数值计算，讨论分析了碎冰区的海冰密集度、冰块面积和几何规则度对冰载荷的影响。

Construction of broken ice field with Voronoi tessellation algorithm and its DEM simulations

The discrete element method (DEM) has been applied to simulate sea ice widely,especially to simulate the dynamic behaviours of broken ice field and its action on offshore structures.To construct the ice floes with special geometry,the Voronoi diagram in two dimension is adopted to generate the initial distribution of broken ice field with tessellation algorithm.The ice floes with irregular shapes are filled with spherical elements.The size of ice floes,geometry and concentration of a broken ice field can be defined with the Voronoi tessellation method.To generate the different shapes of ice floes with various regularities,the exclusion method and the disturbance method are both introduced in this study.To determine the influence of regularities on the geometric characteristics of ice floes,the probability distributions of the ice floe area and edge number are analysed statistically.With the study above,the spherical elements with bonded-broken function are used to simulate the ice load on conical offshore structures in the broken ice field.The influences of ice concentration,area and regularity of ice floes on the ice load are discussed with the DEM results.