Flow-Induced Streamwise Vibration of a Flexibly-Mounted Cantilevered Cylinder in Steady and Pulsating Crossflow

This paper describes an experimental study of the response of a freely vibrating cylinder with low mass ratio and high damping to steady and pulsating crossflow for Reynolds numbers in the range 120–2900. A rigid circular cylinder was cantilevered by means of a plate spring allowing it to oscillate in the stream-wise direction only. A camera-based technique was employed for tracking the cylinder vibration while the wake fluctuations were measured by a laser-Doppler system. The results show that the forced excitation from pulsating flow can take over control of the wake and/or the cylinder oscillations in a complex manner. The overall response depends strongly on two main parameters: the ratios of the pulsation frequency to the structural frequency and to the vortex shedding frequency from a fixed cylinder in steady flow. When the excitation frequency from both the wake and the external pulsation coincided with the natural frequency of the structure, the r.m.s. amplitude of the cylinder vibration increased up to 400% compared to that for the same reduced velocity in steady flow. In this case, maximum end displacements exceeded 35% of the cylinder diameter.