An experimental investigation of dual-resonant and non-resonant responses for vortex-induced vibration of a long slender cylinder

Experimental results of the dual-resonant and non-resonant responses are presented for vortex-induced vibrations (VIV) of a long slender cylinder. The cylinder has a diameter of 10mm and a length of 3.31 m, giving an aspect ratio of 331. The cylinder was towed by a carriage with the velocity up to 1.5 m/s, with the Reynolds number varying from 2500 to 38000. Three different weights were used to provide the initial tension. Dual resonance means that resonance occurs simultaneously in both the cross-flow (CF) and in-line (IL) directions. The experiments were conducted in two stages. At the first stage, dual-resonant dynamic features of the cylinder subjected to vortex-induced excitation were investigated. The features of CF and IL vibration amplitude, motion orbits, phase angle differences, dominant frequencies and mode order numbers are presented. At the second stage of the experiments, particular emphasis was placed on non-resonant dynamic features. The variation of multi-mode modal displacement amplitudes was investigated in detail.