波浪中自由自航船舶轴系功率特性的数值预报方法

Numerical prediction method of shafting power characteristics of free self-propelled ship in waves

[目的]为了研究船舶在波浪中约束模与自航模运动特性的差异以及船舶轴系功率特性,开展船舶波浪中自航性能数值仿真预报。[方法]首先,选取KCS船模和KP505桨模,采用URANS方法进行船舶波浪自由直航CFD模拟;然后,基于自研URANS求解器HUST-Ship与自研结构化动态重叠网格代码HUSTOverset,以及改进型体积力螺旋桨推进模型,对船舶在不同波浪条件下的运动响应进行耦合求解,包括两自由度KCS约束模运动仿真和三自由度自航模自由直航仿真,并对比这2种方法预报船舶运动特性的差异;最后,采用对数分析法得出波浪中船舶自由直航功率增加的主要成分及其具体占比。[结果]KCS船模在波浪中自航时,推进效率和波浪增阻对功率增加的贡献占比分别为23%~26%和74%~77%,即波浪增阻占比较大。[结论]因此,降低波浪中功率增加的最有效方法是减小船舶运动以降低波浪增阻。

[Objective]To investigate ship power characteristics and the difference between the towing model and self-propulsion model for ship motion response in waves, numerical simulations of ship selfpropulsion performance in waves are carried out. [Methods]In this paper, the KCS ship model and KP505propeller model are selected, and the unsteady Reynolds-averaged Navier-Stokes(URANS) method is used to carry out computational fluid dynamics(CFD) simulations of ship self-propulsion in waves. The in-house URANS solver HUST-Ship and in-house structured dynamic overset grid code HUST-Overset are combined to solve the motions of the self-propelled ship in waves, and the improved body-force model is selected as the propulsion model. Towing simulations for KCS with two-degrees-of-freedom(DOF) in waves and selfpropulsion simulations with 3-DOFs under different wave conditions are carried out, and the differences between these methods are discussed in detail. Finally, the components and their specific proportions of added power during ship self-propulsion in waves are analyzed in detail using the logarithmic analysis method.[Results]Regarding the added power of a self-propelled KCS in waves, the added resistance is responsible for 74%-77% while propulsive efficiency accounts for 23%-26%, that is, the added resistance occupy a larger proportion.[Conclusion]Reducing ship motion to decrease added resistance is the most effective approach to reducing added power.