Vortex-Induced Vibrations of a Circular Cylinder Near a Planar Wall Boundary

Abstract

The amplitude response as well as the wake of a low mass ratio circular cylinder undergoing free Vortex-Induced Vibration (VIV) was investigated experimentally in a water tunnel facility. Experimental measurements of the amplitude response and Particle Image Velocimetry (PIV) measurements were conducted as part of the study. Amplitude response data were processed to compute time-averaged and fluctuating quantities. Moreover, Fourier analysis was carried out to identify the frequency content of the cylinder's oscillation. The influence of the driving parameters, namely, the reduced velocity and the gap ratio, on the system's amplitude and frequency response is elucidated. PIV realizations in the wake are used to compute time-averaged quantities, and consequently determine how the driving parameters alter the statistical quantities such as recirculation length and vortex formation length. In addition, a low-order representation (referred to as Low-Order Model, LOM) of the wake was constructed via the truncation of Galerkin expansion modes obtained from Proper Orthogonal Decomposition (POD). The LOM is used to investigate the vortex dynamics and relate the cylinder motion with vortex shedding. The circulation of the shed vortices from the cylinder is estimated to enhance the quantitative description of the vortex formation and shedding process, and to quantify how the wall boundary and the near-wall vorticity interacts with vortex shedding.