可着陆式水下机器人的多体动力学建模与仿真

可着陆式水下机器人由于变浮力机构的设计要求,其外形与结构较之传统的水下航行器更为复杂。在设计阶段对可着陆式水下机器人进行仿真和操纵性分析具有重要意义。文中采用多体系统动力学方法分析可着陆式水下机器人动力学特性,将作用在系统各组成部分上的流体动力、推进力以及其它作用力分别计算和考虑,建立了多体动力学模型,并进行了三维空间运动仿真。该方法为具有较复杂附体结构的水下机器人设计和动力学仿真提供了有效途径。     

小型水下自航行器自沉浮装置设计与研究

文中对水下自航行器(Autonomous Underwater Vehicle,简称AUV)的自沉浮装置进行了详细设计与研究。通过对已有的自沉浮装置方案进行对比研究,设计了以高压气体吹除压载水舱的新型自沉浮装置,该装置具有结构简单、可靠性高和可维护性好的特点,并可实现模块化设计。最后,对装置的主要设计参数进行了计算与优化。     

Influence of cavity shape on hydrodynamic noise by a hybrid LES-FW-H method

The flow past various mechanical cavity, which is a common structure on the surface of the underwater vehicle, and generating hydrodynamic noise has attracted considerable attention in recent years. In this paper, a hybrid method is presented to investigate the hydrodynamic noise induced by mechanical cavities with various shapes. With this method, the noise sources in the near wall turbulences or in the wake are computed by the large eddy simulation (LES) and the generation and propagation of the acoustic waves are solved by the Ffowcs Williams-Hawkings (FW-H) acoustic analogy method with acoustic source terms extracted from the time-dependent solutions of the unsteady flow. The feasibility and reliability of the current method was verified by comparing with experimental data (Wang, 2009). The 2D cavity models with different cross-section shapes and 3D cavity models with different cavity mouth shapes (rectangular and circular) are developed to study the influence of cavity shape on the hydrodynamic noise. By comparing the flow mechanisms, wall pressure fluctuations, near-field and far-field sound propagation distributions, it is found that the quadrangular cavity with equal depths of leading-edge and trailing-edge is preferred for its inducing lower hydrodynamic noise than the cylindrical cavity does.     

Dynamic Modeling and Three-Dimensional Motion Analysis of Underwater Gliders

For Cconsideration ofing both the eccentric rotatable rigid body and the translational rigid body, the dynamic model of the underwater glider is derived. Dynamical behaviors are also studied based on the model and can be used as the guidance to underwater gliders design. Gibbs function of the underwater glider system is derived first, and then the nonlinear dynamic model is obtained by use of Apell Equations. The relationships between dynamical behaviors and design parameters are studied by solving the dynamic model. The spiral motion, swerving motion in three dimensions and the saw-tooth motion of the underwater glider in vertical plane are studied. Lake trials are carried out to validate the dynamic model.     

拖曳系统拖曳动态过程仿真分析

对于海洋缆索系统,论文针对传统有限段法的不足,提出改进的缆索有限段法,缆索离散为若干弹性缆段组成的多柔体系统,根据缆索的特点选择适当的参考系和广义速率,引入有限元法中的形函数描述段内各点位移,根据Kane方程推导改进缆索有限段模型的运动方程。基于改进的缆索有限段法,提出了模拟拖曳缆索释放一回收过程的变拓扑结构模型,即用可变长度缆段长度的变化和缆段数量的改变建模缆索的释放和回收过程。文中对一海洋拖曳系统进行了动力学仿真,与海洋试验结果比较验证了模型的正确性。     

海洋缆索的动力学仿真研究

论文研究了多体有限段模型中缆索弹性的两种处理方法：段间弹簧模拟弹性和采用弹性缆段。处理弹性问题,弹性缆段是一个更好的选择,它将多体运动力学和弹性力学结合起来,建立了由弹性缆段组成的多体有限段模型,理论上,这种方法对弹性的处理效果类似采用杆单元考虑几何非线性的有限元法,用于求解运动响应。水下缆索的附加质量作用性质与缆索自身惯性相同,文章将其归入了广义惯性力,并将其它流场力等效为多体方法需要的作用于质心的力系。     

Dynamic Modeling and Three-Dimensional Motion Analysis of Underwater Gliders

For consideration of both the eccentric rotatable rigid body and the translational rigid body, the dynamic model of the underwater glider is derived. Dynamical behaviors are also studied based on the model and can be used as the guidance to underwater gliders design. Gibbs function of the underwater glider system is derived first, and then the nonlinear dynamic model is obtained by use of Appell equations. The relationships between dynamic behaviors and design parameters are studied by solving the dynamic m...     

Dynamic Analysis of Towed and Variable Length Cable Systems

Towed cable systems are frequently used in marine measurements where the length of the towed cable varies during launch and recovery. In this paper a novel method for modeling variable length cable systems is introduced based on the finite segment formulation. The variable length of the towed cable is described by changing the length of the segment near the towing point and by increasing or decreasing the number of the discrete segments of the cable. In this way, the elastic effects of the cable can be easily handled since geometry and material properties of each segment are kept constant. Experimental results show that the dynamic behavior of the towed cable is consistent between the model and the physical cable. Results show that the model provides numerical efficiency and simulation accuracy for the variable length towed system.