Two-degree-of-freedom flow-induced vibrations on isolated and tandem cylinders with varying natural frequency ratios

2012 ◽  
Vol 35 ◽  
pp. 50-75 ◽  
Author(s):  
Yan Bao ◽  
Cheng Huang ◽  
Dai Zhou ◽  
Jiahuang Tu ◽  
Zhaolong Han
Keyword(s):  
Natural Frequency ◽  
Degree Of Freedom ◽  
Tandem Cylinders ◽  
Flow Induced Vibrations ◽  
Frequency Ratios ◽  
Two Degree Of Freedom

scholarly journals Response of a Two-Degree-of-Freedom Vibration System with Rough Contact Interfaces

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Zhiqiang Huang ◽  
Xun Peng ◽  
Gang Li ◽  
Lei Hao
Keyword(s):  
Natural Frequency ◽  
Degree Of Freedom ◽  
Element Analysis ◽  
Chaotic Motions ◽  
First Order ◽  
Vibration Properties ◽  
Ground System ◽  
Jump Frequencies ◽  
Two Degree Of Freedom ◽  
Seismic Vibrator

This paper is focused on the influence of the rough contact interfaces on the dynamics of a coupled mechanical system. For this purpose, a two-degree-of-freedom model of a coupled seismic-vibrator-rough-ground system is proposed with which the nonlinear vibration properties are analyzed. In this model, the force-deflection characteristic of the contact interfaces is determined by finite element analysis. By analyzing the undamped free vibration, it was found that the variation of the second-order natural frequency with amplitude increases with rougher contact interfaces; however, the amplitude has little influence on the first-order natural frequency of the system. For the harmonic excited analysis, the jump frequencies and hysteretic region both decrease with rougher contact interfaces. Moreover, it is inferred from the bifurcation diagrams that, increasing the excitation force, the system can bring about chaotic motions on rough contact interfaces.

Tuned mass damper and high static low dynamic stiffness isolator for vibration reduction of beam structure

2019 ◽  
Vol 234 (1) ◽  
pp. 95-115 ◽  
Author(s):  
Meysam Raei ◽  
Morteza Dardel
Keyword(s):  
Natural Frequency ◽  
Dynamic Stiffness ◽  
Excitation Amplitude ◽  
Tuned Mass Damper ◽  
Degree Of Freedom ◽  
Negative Stiffness ◽  
Low Frequencies ◽  
First Case ◽  
Mass Damper ◽  
Two Degree Of Freedom

In this work, the combination effect of tuned mass damper and high static low dynamic stiffness (HSLDS) isolator is investigated in reducing the vibration amplitude of Euler–Bernoulli beam with a nonlinear attachment. The performance of the absorber is studied in two cases; the first case, HSLDS isolator is one degree of freedom and the second case, two degree of freedom isolator is combined of HSLDS isolator and tuned mass damper absorber. By comparing the performance of these two isolators, it is revealed the two degree of freedom isolator has much better performance in direct force excitation and also improves the system performance in the base excitation. This isolator reduces the system amplitude at all frequencies, especially ultra-low frequencies, which is the main advantage to this isolator with respect to other isolators and reduces the natural frequency until the phenomenon of resonance occurs at a lower frequency. Moreover, decreasing the natural frequency increases the damping and in quasi zero stiffness and negative stiffness structure, the system has supercritical damping. This isolator is studied for positive, quasi zero and negative stiffness. The results show that the system with quasi zero stiffness has the best performances. Also, by increasing the excitation amplitude, the isolator loses its effectiveness.

Two-Degree-of-Freedom Flow-Induced Vibrations of a Circular Cylinder With a High Moment of Inertia Ratio

2010 ◽  
Author(s):  
Sina Kheirkhah ◽  
Serhiy Yarusevych
Keyword(s):  
Damping Ratio ◽  
Moment Of Inertia ◽  
Degree Of Freedom ◽  
High Moment ◽  
Near Wake ◽  
Synchronization Region ◽  
Vortex Induced Vibrations ◽  
Experimental Parameters ◽  
Flow Induced Vibrations ◽  
Two Degree Of Freedom

Two degree-of-freedom vortex-induced vibrations of a moderate mass and high moment of inertia ratio pivoted cylinder were investigated experimentally. The experiments were performed at a constant Reynolds number of 2100 for a range of reduced velocities from 3.4 to 11.25. The results show that, in addition to the reduced velocity, the transverse damping ratio has a significant effect on the amplitudes of response. The cylinder tip is observed to trace orbital trajectories, which is shown to be attributed to the frequencies of oscillations in both directions locking onto the natural frequency in the synchronization region. The results indicate that a phase angle between the streamwise and transverse oscillations governs the direction and orientation of the orbiting motion. Flow visualization results show that, at a given reduced velocity and transverse damping ratio, near-wake development changes along the cylinder span. The observed shedding patterns are shown to differ from those expected at the corresponding experimental parameters for one-degree-of-freedom uniform amplitude cylinder vibrations.

Two-degree-of-freedom flow-induced vibration of two rigidly coupled tandem cylinders of unequal diameters

2020 ◽  
Vol 216 ◽  
pp. 108142
Author(s):  
Hongjun Zhu ◽  
Xiaonian Tan ◽  
Yun Gao ◽  
Tongming Zhou ◽  
Wenli Liu
Keyword(s):  
Degree Of Freedom ◽  
Flow Induced Vibration ◽  
Tandem Cylinders ◽  
Two Degree Of Freedom
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