A note on the fluid damping of an elastic cylinder in a cross-flow

This note reports an experimental study of the fluid damping of a long slender cylinder, fixed at both ends (no rotation and displacement), in a cross air-flow. The structural dynamic strain was measured in the lift direction over a range of reduced velocity Ur using a fibre-optic Bragg grating sensor. An auto-regressive moving average technique was used to deduce the effective damping ratios (including structural and fluid damping) from the strain data. The modal damping ratios corresponding to the first-, second- and third-mode vibrations over a range of Ur from 3 to 45 have been characterized and discussed. The results show that the value of fluid damping varied significantly at resonance when the vortex-shedding frequency coincides with one of the natural frequencies of the combined fluid–structure system.