Experimental investigation of Reynolds number and spring stiffness effects on vortex induced vibrations of a rigid circular cylinder

Abstract

Abstract The Vortex Induced Vibration for Aquatic Clean Energy (VIVACE) is a breakthrough technology, which harvests the hydrokinetic energy of ocean currents through enhancing Vortex Induced Vibration (VIV). In this paper, the VIV of an elastically mounted circular cylinder in a towing tank water channel is studied experimentally to investigate the effect of natural frequency, by using five different springs in a wide range of stiffness (125 N/m × 104 × 104) with high mass-damping parameter (m* ζ = 0 .11). Results demonstrated the strong dependency of VIV on natural frequency and lock-in observed in a broad range of spring stiffness. Moreover, the studied Re range showed the gradual transition between two distinct turbulence shear layers from previously published works at Re ≈ 4,000 to Re ≈ 100,000. The amplitude ratio and range of synchronization in the upper branch increases by spring stiffness. The lower branch of response disappeared due to the high mass-damping parameter in conducted experiments. These observations suggested to employ an adjustable natural frequency system to have an optimum energy harvesting in VIV-based ocean energy converters in an expanded range of operation.