变质量贮箱类流固耦合系统的振动响应及时频特性分析

摘要

研究了变质量贮箱类流固耦合系统的动力学特性。根据虚拟质量法，使用有限单元法构建了变质量贮箱类流固耦合系统的动力学模型，建模过程中着重考虑了质量变化对系统的影响。通过 Newmark 直接积分法计算出变质量贮箱时变系统的振动响应，分析了不同质量变化率对变质量贮箱系统动力响应的影响，并借助平滑伪 Wigner －Ville 变换获得变质量贮箱时变系统的动力响应时频谱。结果表明：由于系统质量减少，引起了系统振动频率的增大，并产生一个附加的负阻尼。这个负阻尼的大小与系统的质量变化率成正比。对比不同质量变化率和不同结构阻尼变质量贮箱的动力响应及时频特性，系统的振动频率的范围可以通过系统质量的范围确定，而且当附加负阻尼的作用超过系统结构阻尼的作用时，会使得系统的振动振幅增大，引起系统的不稳定。平滑伪 Wigner －Ville 变换是处理非平稳信号的一种有效工具。%Here,dynamic responses and time-frequency feature analysis for a fluid-structure coupling system with a variable mass tank were performed.A finite element dynamic model was established by using the virtual mass method considering the influence of mass varying.The responses of the time-varying mass tank system were calculated by using Newmark direct integration method.The effects of time varying mass on the dynamic responses of the tank system were investigated.The time-frequency features of the fluid-structure coupling system were obtained by using the smoothed pseudo-Wigner-Ville transformation (SPWVT).Results showed that the decrease in mass induces the increase in the vibration frequencies of the system,and generates an additional negative damping;the additional negative damping is proportional to the change rate of the system mass;based on the dynamic responses and the time frequency analysis for different conditions,the frequency range of the system can be determined with the range of the system mass;the additional negative damping causes the vibration to decay slowly,and the additional negative damping can cause the system to vibrate with increasing amplitudes when the mass changes rapidly;the smoothed pseudo-Wigner-Ville transformation is an effective tool to deal with nonstationary signals.