破冰船引航下极地船舶结构冰荷载的离散元分析

采用破冰船引航的方式可有效保障商船在极地冰区的航行安全。通过基于闵可夫斯基和原理的扩展多面体构造任意形态的海冰单元，同时发展基于扩展多面体单元的粘结失效模型模拟海冰的破碎过程，从而建立基于扩展多面体的离散元方法。采用扩展多面体离散元方法模拟船舶冰区航行过程中的船-冰相互作用，并分析船舶结构上的冰载荷。根据“雪龙号”船体结构模型，采用扩展多面体离散元方法模拟了单船破冰条件下的冰荷载，通过船舶抗冰设计中常用的冰阻力Lindqvist公式和Riska公式校核离散元计算结果。对比结果表明，扩展多面体离散元方法与相关公式计算结果相近，对船舶结构冰荷载的模拟精度较好。采用离散元方法计算了引航条件下破冰船和货船上的冰荷载，分析不同航速和船宽比条件下两船上的冰阻力大小和特点。扩展多面体离散元方法可有效用于船舶结构的冰荷载分析，其计算结果可为冰区船舶设计和航行安全提供重要参考。

Discrete element analysis of ice loads on polar ships under pilotage of icebreaker

The pilotage of icebreaker can effectively guarantee the navigation safety of merchant ships in polar ice regions. The dilated polyhedron based on the Minkowski sum theory is used to generate the sea ice element with irregular shapes. The bond-failure model of the dilated polyhedron element is developed to simulate the breaking process of sea ice. Accordingly a dilated polyhedron based discrete element method (DPDEM) is established. The interaction between ship hull and sea ice is simulated with the DPDEM, while the ice load on the ship hull is analyzed. The ice load on ship hull which is based on the hull model of icebreaker Xuelong is simulated using the DPDEM. The result is validated with the result of the Lindqvist formula and the Riska formula which are most commonly used for the ice load analysis on ship hull. The validation illustrates that the results by the DPDEM and the empirical formula are close. It is convincing that the DPDEM can be used for the ice load analysis on ship hull. Moreover, the ice loads on ships under the pilotage of icebreaker is simulated using the DPDEM. The ice resistance under different ship speed and ratio of ship width is analyzed. The DPDEM can effectively be used for the analysis of ice load on the ship hull. The results by the DPDEM can provide important references for the ice ship design and navigation safety.