﻿ 基于显式动力学理论的冰桨碰撞数值分析
 舰船科学技术  2020, Vol. 42 Issue (1): 32-37 PDF

Numerical analysis of ice and collision based on explicit dynamics theory
HAN Xu, LIU Ai-hua, LIU Han-qiu
School of Energy and Power Engineering, Wuhan University of Technology, Wuhan 430063, China
Abstract: When the ship is sailing in an ice environment, the propeller inevitably collides with the ice. Aiming at the ice and propeller collision problem in ice area, basing on the explicit dynamics theory, the propeller of a multi-purpose ship is the research object, and the ice and propeller collision model is established. The Ansys finite element calculation method is used to analyze the dynamic effects of different speeds, different collision position, different sizes of ice on the propeller collision. The results show that the ice mass velocity, collision location and ice size have a significant impact on the damage of the propeller., and the collision regular pattern between the ice and propeller is qualitatively obtained.
Key words: ice     ship propeller     collision     ice load
0 引　言

1 显式动力学方程

 ${a_t} = {M^{ - 1}}\left( {F_t^{ext} - F_t^{int}} \right){\text{。}}$ (1)

 $F_t^{int } = \sum {\left( {\int {{B^{\rm T}}{\sigma _n}{\rm d}\varOmega + {F^{hg}}} } \right) + {F^{contact}}} {\text{。}}$ (2)

 ${V_{t + \Delta t/2}} = {V_{t - \Delta t/2}} + {a_t}\Delta {t_t}{\text{，}}$ (3)
 ${u_{t + \Delta t}} = {V_t} + {V_{t + \Delta t/2}}\Delta {t_{t + \Delta t/2}}{\text{，}}$ (4)

 $\Delta {t_{t + \Delta t/2}} = 0.5\left( {\Delta {t_t} + \Delta {t_{t + \Delta t}}} \right){\text{。}}$ (5)

 ${x_{t + \Delta t}} = {x_0} + {u_{t + \Delta t}}{\text{。}}$ (6)

 $\Delta {\rm{t}} \leqslant \Delta {t_{ct}} = \frac{2}{{{\omega _{\rm{max} }}}}{\text{。}}$ (7)

 $\left| {{K^e} - {\omega ^2}{M^e}} \right| = 0{\text{。}}$ (8)
2 冰—桨模型

 图 1 冰块模型 Fig. 1 Ice model

 图 2 螺旋桨模型 Fig. 2 Propeller model

 图 3 螺旋桨网格划分模型 Fig. 3 Propeller meshing model

 图 4 冰和桨碰撞模型 Fig. 4 Ice and propeller collision model
3 冰—桨碰撞分析

3.1 碰撞速度的影响分析

 图 5 不同速度部分时刻桨叶应力云图 Fig. 5 Blade stress contours at different speed

 图 6 不同速度部分时刻桨叶的变形云图 Fig. 6 Blade stress deformation at different speed

 图 7 最大应力时历曲线 Fig. 7 Maximum stress-time curve

 图 8 最大变形时历曲线 Fig. 8 Maximum deformation-time curve
3.2 碰撞位置影响分析

 图 9 各工况受力区域示意图 Fig. 9 Schematic diagram of the force area of each working condition

 图 10 海冰初始时刻与冰块的相对位置 Fig. 10 The relative position of the sea ice at the initial moment to the ice

 图 11 最大应力时历曲线 Fig. 11 Maximum stress-time curve

3.3 冰块大小影响分析

 图 12 最大应力时历曲线 Fig. 12 Maximum stress-time curve

 图 13 最大变形时历曲线 Fig. 13 Maximum deformation-time curve

4 结　语

1）桨叶受到的应力和冰块的速度大小有关。随着冰块运动速度的增加，桨叶受到的撞击力越大，发生的变形也越大，螺旋桨越容易发生损坏。桨叶受到的最大应力位于桨叶与桨轴的连接位置，可见碰撞过程中冲击力由碰撞位置传递到桨轴处，桨叶的最大变形开始主要集中在碰撞区域附近，之后最大变形位于桨叶边缘。

2）冰桨接触力主要取决于接触面积。由于桨叶整体较薄，桨叶厚度对碰撞影响不大。冰桨接触力的大小与冰块强度和接触面积有关，由于工况3、工况4、工况5冰块的情况完全一样，因此接触面积的不同导致了冰桨接触作用力的差别。

3）冰块的尺寸对碰撞有很大影响。冰块边长为0.2 m时桨叶受到的最大应力为460.15 MPa，变形为11.77 mm要明显大于0.1 m时的最大应力166.86 MPa和3.44 mm。因此冰块尺寸越大，碰撞后对桨叶的损害也越大。

4）螺旋桨受损最明显的地方是桨叶边缘，因此螺旋桨在设计时可以适当增大桨叶的厚度，从而提高结构刚度和承载能力。

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