Wavelet Analysis of FIV Response for Single Cylinder and Pairs of Cylinders in Tandem and Side-by-Side

Abstract Flow induced vibration of a single cylinder and two cylinders assembled in the configurations tandem and side-by-side are experimentally investigated in the present study. The rigid cylinder free to vibrate is fixed in two blades, forming two different configurations, to allow transversal and longitudinal vibration, respectively. The mass ratio, m* ranged between 158 and 643 while the damping ratio, ζ, ranged between 0.0006 and 0.005. The pairs of cylinders present a space ratio of 1.26 (P/D and L/D) and one of the cylinders is fixed while the second one is free to vibrate. The aerodynamic channel used in the analysis presents test section with 0.146m height and 0.193m width, the study is executed using accelerometer and hot wire anemometry. The velocity on the test section is varied and generates reduced velocity, Vr = U/fnD, between 4 and 30. The displacement amplitudes, Y/D, are obtained using integration of the acceleration signals, and the root mean square results are adopted. Fourier spectral analysis and continuous wavelets are employed in the analysis of acceleration and velocity signals. The higher amplitudes happen in two distinct reduced velocities and were associated with the vibration modes of the cylinder free to vibrate. In the case with two cylinders side-by-side the amplitude is higher and present small variation on the reduced velocity of occurrence in comparison with single cylinder. For the case with cylinders in tandem the presence of the cylinder in the wake of the cylinder free to vibrate generated amplification of the response in high reduced velocities.