弹性桨-轴系统建模与计算方法研究

Investigation on the modelling and computational algorithm for fluid-structure interactions of propeller-shafting systems

弹性桨-轴与流体产生的双向流固耦合效应,显著改变了推进系统振动性能。现有研究分别针对桨叶和转轴弹性采用分离模型进行,即:流体-弹性桨与流体-刚体桨-弹性轴模型。而在实际工况中,转轴由于发生振动,使弹性桨入流条件与忽略轴系振动时的差异很大;另一方面,现有分离模型在预报时,是基于流体在桨叶振动平衡位置处界面力学关系开展的,未能真实反映流体在振动桨叶物理表面行为特征,难以满足桨-轴系统振动特性准确预报的现实需求。该研究拟针对流体-弹性桨-轴复杂系统双向流固耦合问题,基于精确的振动桨叶表面流体界面力学关系,建立弹性桨-轴双向流固耦合一体化模型并发展一套高效高精度稳定数值算法。结果表明,船舶研究者需建立流体-弹性桨-轴一体化模型,以重新评估附加质量/阻尼及轴承处激励力。建立的模型与算法和得到的结果可为低速水下航行器声振性能设计和评价提供理论和技术支持。

The interaction between the propeller-shafting system and the fluid around the propeller may significantly affect the dynamic performance of the propulsion system.The traditional methods for investigating this phenomenon are based on the uncoupled fluid-propeller(elastic vibration)/fluid-propeller(six degrees rigid body oscillation)-shafting models,which consider the elasticities of the blades and shaft separately.Since the propeller is attached to the elastic shafting system,the elastic behavior of the shafting system may affect the incoming flows.In addition,previous uncoupled analyses pertaining to this problem were based on the interface conditions of the fluid and the structure,which are imposed on the undeformed blade surface.It is difficult to capture the dynamic behavior of the fluid on the physical surface of the vibrating blades.The vibration characteristics of the propeller-shafting system cannot be accurately predicted by this method.Based on the boundary condition on the fluid-structure interface of the vibrating blades,numerical models are established for two-way strongly coupled fluid-structure interaction analysis of the propeller-shafting system.A stable algorithm of high efficiency and accuracy is developed to study the unsteady hydrodynamic performance of the fluid-propeller-shafting coupled system.It is found that the designers need to consider the elastic coupling effect between the shaft and the propeller for re-evaluation of additional mass/damping and excitation forces at bearings.The developed methods and the results may provide effective theoretical reference and technical support for the design and evaluation of the vibration characteristics of low-speed underwater vehicles.