Mitigating flow-induced vibration of a flexible circular cylinder via pre-tension

This paper studies the effects of pre-tension on flow-induced vibration of a flexible cylinder with two degrees of freedom in a towing tank. A 0.45 m section of Tygon tubing with an outer and inner diameter of 7.9 mm and 4.8 mm respectively, was employed as a flexible test model, the mass ratio and aspect ratio of which is 0.77 and 57, respectively. It was towed from rest up to 0.8 m/s before slowing down to rest again over a distance of 1.6 m in still water with three cases of pre-tension from 0 to 8 N. The Reynolds number based on the cylinder's outer diameter spanned from approximately 780-6300 while the reduced velocity ranged from 2 to 16. Emphasis was on revealing the possible relationship between pre-tension and response amplitude as well as the frequency. The vibration amplitude and frequency obtained during the brief constant towing speed were quantified and expressed in terms of reduced velocity. Narrowed lock-in bandwidth and reduced response amplitude were observed. The findings from this set of experiments are compared to the existing knowledge in the literature.