Vortex induced vibrations experiments on a flexible cylinder

Vortex Induced Vibrations experiments have been carried out with a clamped and long flexible cylinder, suspended from a towing tank carriage. The lock-in phenomenon has been observed through bending strain measurements taken along the tube span, within a range of speeds - Reynolds number varying from 6x10(3) to 4x10(4) -fully exciting the first flexural eigenmode. The experiment set up as well as analysis procedures are described herein. Experimental results clearly show two resonance branches, in accordance with similar experiments, performed in water, with rigid cylinders mounted in linearly elastic supports; Khalak & Williamson, (1996), Parra (1996). The upper branch of oscillation occurs for higher reduced velocities than in the case of rigid models. A jump phenomenon, from the lower to the upper branch, has been observed giving further evidences of a hysteresis scenario, as discussed by Brika & Laneville (1993), Khalak & Williamson (1996) and firstly addressed by Feng(1968).