不同来流作用下管道失稳机理及流固耦合非线性动力学研究

The flow-induced vibration of pipes widely exist in nature. The instability mechanism and dynamics of pipes are severely complicated. The research on this subject intends to investigate the instability mechanism and nonlinear dynamics of pipes subjected to internal axial flow, external axial flow, external cross flow, and combined internal and external flow, both theoretically and experimentally.. The main contributions of the research can be summarized as follows: Firstly, based on Euler-Bernoulli beam theory, a nonlinear partial differential equation of motion of the pipe will be derived from Hamilton’s principle. The nonlinear equations of motion of the pipe, coupled with continuity equation and Navier-Stokes equations for the fluid-dynamic model, will be used to analyze the stability and post-critical dynamical behaviour of this fluid-structure system theoretically. The formula of fluid pressure acting on the pipe will be derived based on potential flow theory. The partial differential equation of motion of the pipe is discretized involving the use of the Galerkin method, and the resulting set of nonlinear ordinary differential equations is solved by Houbolt’s finite difference method. Secondly, experimental setups for the research on fluid-structure interaction of the pipes will be built. Finally, the vibration behaviours of the pipe induced by the excitation of wave loads and the seismic loads will be investigated. . The objective of the research is to study the instability mechanism, the bifurcation characteristics and the nonlinear dynamical bahaviours of the pipe subjected to various flow conditions, analyze the influence of the stiffness, the material damping, the flow velocity and the viscous drag coefficient on the dynamics of the system, and investigated the lock-in phenomenon and hysteresis phenomenon of the pipe during oscillation.

管道由于流体诱发的振动普遍存在，其失稳机理及动力特性十分复杂。本课题拟通过理论分析、数值模拟和实验研究，开展管道在轴向内流、轴向外流、横向外流、以及内外流共同作用下的失稳机理及非线性动力学研究。. 首先，基于Euler-Bernoulli梁理论，采用Hamilton变分原理，推导管道非线性运动方程，基于流体连续性方程和管运动方程，推导流体作用在管道上的压力计算式，建立管道流固耦合模型，采用Galerkin法和Houbolt法求解非线性方程，理论研究不同来流下管道失稳及流固耦合动力特性；其次，构建管流固耦合试验台，开展不同来流下管流固耦合振动试验研究；最后，开展波浪、地震载荷激励下管道振动特性研究。. 本课题旨在研究管道在不同来流作用下的失稳机理、分叉行为和振动特性，分析结构刚度、阻尼系数、流体流速和粘性阻力系数对系统动力特性的影响，探求管道振动锁定和滞回现象形成机理。

流体诱发管道振动的情况普遍存在于能源、机械等多个领域中，本课题旨在通过理论分析、数值模拟和实验研究等方法，开展管道在内流、外流和其他外在激励等多因素影响下的失稳机理及相关动力学特性。. 本课题首先开展管道外流作用下的不同管束结构的振动和流体弹性失稳过程研究；针对核电站内RIC指套管在外流作用下的管道振动变形过程及磨损分析；进行振动单管换热流场数值模拟研究，针对不同振动频率，振幅，振动角下的管道振动带来的热力学特性展开分析和研究。其次开展内流作用下的管道甩击性能研究，分析高能管道环向断裂后管道甩击过程中的动力学行为，以及不同设计、安装参数下的防甩装置引起的甩击抑制效果。最后，开展纵倾平衡管系在水锤冲击激振影响下的振动特性以及相应水锤控制方案研究。研究不同工况下的纵倾平衡系统管系压力变化，研究水锤激振下的管系动力特性，分析纵倾平衡系统水锤和管系振动噪声特性，并针对相应问题研究水锤控制方案，维护纵倾平衡系统的安全运行。. 本研究最终通过研究内流、外流以及水锤激励等因素造成管道振动的作用机制，揭示了外流作用下管道振动变形过程及磨损规律，得到了影响振动圆管换热性能的内在机理，研究了管道破裂后的防甩系统的安装方法，建立了水锤激振预报技术，提出了抑制水锤引发管道振动的实际方案。