刚柔混合输流管的流致振动稳定性研究

STABILITY RESEARCH OF FLOW⁃INDUCED VIBRATION OF HYBRID RIGID⁃FLEXIBLE PIPE CONVEYING FLUID

弹性管和刚性管串联而成的混合输流管是典型的刚柔耦合系统。基于Hamilton原理,建立了刚柔混合输流管的动力学模型,利用悬臂梁的模态函数对方程进行Galerkin离散,分析了混合管的流致振动稳定性问题,讨论了两管连接处转动弹簧的刚度、刚性管与弹性管的质量比和长度比对系统临界流速的影响。结果表明,刚性管长度比的增加能显著降低混合管的临界流速,并且主要发生2阶模态失稳。当刚度和质量比取某些值时,随着内流流速的增加,混合管可能出现“失稳(2阶模态)-稳定-再失稳(3阶模态)”的变化过程。此外,随着弹性管质量比的增加,还观察到了混合管由2阶模态过渡到4阶模态的失稳模式。

An articulated pipe composed of a flexible pipe and a rigid pipe is a typical hybrid rigid⁃flexible dynamical system involving flow⁃induced vibrations.Based on Hamilton′s principle,the governing equations of motion of the hybrid rigid⁃flexible pipe system were established.The partial differential equations of motion were discretized via Galerkin′s approach using the modal functions of a cantilevered beam.Instabilities and critical flow velocities were analyzed and calculated as a function of the stiffness of the rotational spring,mass ratio,length ratio of the rigid and flexible pipes.The results show that the critical velocities decrease as the increasing of length ratio and the system mainly suffers second mode instability.The hybrid pipe undergoes complicated transference of“second mode instability⁃regain stability⁃third mode instability”at a certain value of stiffness when the flow velocity increases.With the increasing of mass ratio of flexible pipe,a transition from second mode instability to fourth mode instability is observed.