Vortex-induced vibration of a tube array with a large pitch-to-diameter ratio value

Bin Jiang,Xu Zhang,Xiaoming Xiao,Luhong Zhang

doi:10.1177/1687814016654604

Abstract

To study the vortex-induced vibration behaviors of tube arrays with large pitch-to-diameter ratio values, an experiment has been conducted by testing the responses of an elastically mounted tube in a fixed normal triangular tube array with five rows and a pitch-to-diameter ratio value of 2.5 in a water tunnel subjected to cross-flow. The amplitude curves, power spectral density, and response frequencies were obtained in both in-line and transverse directions through the experiment. The results show that the responses obtained from the in-line direction are quite different from those obtained from the transverse direction. In the in-line vibration, there were two excitation regions, yet in the transverse vibration, there was only one excitation region. Moreover, in the in-line vibration, two obvious prominent peaks can be observed in the power spectral density of the vibration signal. The second prominent peak is a subharmonic peak. The frequency corresponding to the subharmonic peak was nearly twice as high as that corresponding to the first peak. However, in the transverse vibration, only a single broad peak existed in the power spectral density of the vibration signal. The hysteresis and the “lock-in” phenomena appeared in both the in-line and transverse vibrations. The results of study are beneficial for designing and operating devices mounted with large pitch-to-diameter ratio tube arrays, and for further research on the vortex-induced vibration of tube arrays.

Highlights

Vortex-induced vibration plays an important role in the field of fluid–structure interactions
Where UN is the freestream velocity in front of the tube array, P is the pitch of the tube array, D is the outer diameter of the tube, Up is the pitch flow velocity, and fn is the natural frequency of the tube in water in the in-line or the transverse direction
The following conclusions could be drawn from this work: 1. There were two excitation regions in the in-line vibration

Summary

Introduction

Vortex-induced vibration plays an important role in the field of fluid–structure interactions. The case of the vortex-induced vibration of tube arrays is one of the most basic and remarkable cases in the general subject of fluid–structure interactions. It is of theoretical and practical value to analyze the tube arrays vibration in many fields of engineering, such as in the designs for heat exchangers, cooling systems for nuclear power plants, offshore structures, buildings, chimneys, power lines, struts, grids, screens, and cables, in both air and water flow.[1,2,3,4,5,6,7]. In the case of tube arrays with small P/D values, the instability behaviors are often caused by fluid-elastic instability and the vortex formation is impeded by neighboring tubes.[8,9,10]

Methods

Results

Conclusion