BEM/FEM耦合螺旋桨静强度计算方法

Calculation of marine propeller static strength based on coupled BEM/FEM

[目的]螺旋桨强度的可靠性与船舶安全航行直接相关。为了快速且准确地计算螺旋桨强度,[方法]将边界元(BEM)和有限元法(FEM)耦合开发螺旋桨强度预报程序。运用低阶边界元法程序对螺旋桨进行水动力性能计算,并使用普朗特—许力汀平板摩擦阻力公式进行粘性修正,然后将计算得到的桨叶表面压力和粘性修正力作为有限元法结构计算的面力输入。针对螺旋桨结构形状的特殊性,发展实体螺旋桨有限元结构单元的自动划分方法,运用有限元结构计算方程计算出螺旋桨在表面压力和体积力作用下的应力与位移分布。以DTRC 4119模型桨为例,对提出的方法进行收敛性和网格无关性分析,并与文献的有限元软件计算结果进行比较,以验证其有效性。[结果]计算结果表明,提出的方法能够准确计算螺旋桨的应力和位移分布。[结论]该方法避免了人工建模及有限元网格划分的过程,具有实施程序简便、计算效率高等优点,可嵌入到螺旋桨的理论设计和优化设计过程中,形成快速计算螺旋桨强度的能力,提高螺旋桨设计的效率。

[Objectives]The reliability of propeller stress has a great influence on the safe navigation of aship. To predict propeller stress quickly and accurately,[Methods]a new numerical prediction model isdeveloped by coupling the Boundary Element Method(BEM)with the Finite Element Method(FEM). Thelow order BEM is used to calculate the hydrodynamic load on the blades, and the Prandtl-Schlichting platefriction resistance formula is used to calculate the viscous load. Next, the calculated hydrodynamic loadand viscous correction load are transmitted to the calculation of the Finite Element as surface loads.Considering the particularity of propeller geometry, a continuous contact detection algorithm is developed;an automatic method for generating the finite element mesh is developed for the propeller blade; a codebased on the FEM is compiled for predicting blade stress and deformation; the DTRC 4119 propeller modelis applied to validate the reliability of the method; and mesh independence is confirmed by comparing thecalculated results with different sizes and types of mesh.[Results]The results show that the calculatedblade stress and displacement distribution are reliable. This method avoids the process of artificialmodeling and finite element mesh generation, and has the advantages of simple program implementationand high calculation efficiency.[Conclusions]The code can be embedded into the code of theoretical andoptimized propeller designs, thereby helping to ensure the strength of designed propellers and improve theefficiency of propeller design.