基于近场动力学数值方法的冰-吊舱推进器接触判断研究

RESEARCH ON CONTACT JUDGMENT OF ICE-PODDED PROPULSOR BASED ON NUMERICAL METHOD OF PERDYNAMICS

吊舱推进器在极地船舶中的应用,可避免冰区航行中转向、调头困难等操纵问题,是极地船舶广泛采用的推进形式.在冰-吊舱推进器切削过程中,吊舱推进器受到了极端冰载荷的作用,对吊舱推进器结构强度和极地船舶的安全性带来严重的危害.为了研究不同操纵状态的吊舱推进器与冰切削时冰载荷的变化规律,首先,详细介绍了近场动力学方法研究物体断裂问题的理论基础,分析该方法模拟冰材料的可行性.基于近场动力学方法和面元法耦合推导了适用于冰破碎问题模拟的材料破坏准则和冰载荷计算方法.其次,提出了不同操纵状态的吊舱推进器与冰的接触判断方法,建立了冰-吊舱推进器切削状态的数值计算模型,实现了冰-吊舱推进器切削动态变化过程的数值仿真.最后,分析了吊舱推进器在直航、斜航以及操舵状态与冰切削时冰块破碎、螺旋桨和桨叶冰载荷以及吊舱单元整体扭矩的变化情况.计算结果表明:本文提出的不同操纵状态的吊舱推进器与冰切削时的接触判断方法能够真实地模拟冰-吊舱推进器的切削过程,并能获得该过程中冰块的破坏现象和冰载荷变化特性,可为冰区海洋结构冰载荷数值预报技术的发展、冰区吊舱推进器结构的优化设计和运营提供指导.

The ice-going ship with podded propulsor can avoid maneuverability problems,such as changing direction,turning round and so on,when navigating in the ice-covered waters.Therefore,the podded propulsor is widely used in ice-going ship.In the milling process of ice-podded propulsor,podded propulsor is subjected to extreme ice load,which brings serious harm to the structural strength of podded propulsor and the safety of ice-going ship.In order to study the change regularities of ice load in the process of podded propulsor with different maneuvering states and ice milling,first of all,the theoretical basis of the peridynamic method to study the fracture problem of objects is introduced in detail in the paper,and the feasibility of the method to simulate ice material is analyzed.Based on the coupling of the peridynamic method and the panel method,the material failure criterion for ice breaking simulation and the ice load calculation method suitable are derived.Secondly,a method to judgment the contact between podded propulsor with different maneuvering states and ice in the milling process is proposed.The numerical calculation model of ice-podded propulsor milling state is established,and the numerical simulation of ice-podded propulsor milling dynamic process is realized.Finally,the changes of ice breaking,ice load of propeller and single blade,overall torque of podded unit during podded propulsor with straight ahead,azimuthing condition,dynamic azimuthing condition and ice milling are analyzed.The results show that the contact judgment method proposed in this paper can real simulate the milling process of the ice-podded propulsor,and obtain the ice breaking phenomenon and ice load variation characteristics in the process.It can provide guidance for the development of numerical prediction technology for ice load on marine structure in ice area,the optimization design and operation of ice class podded propulsor.