Characterizing Vortex-Induced Vibrations of a 3D Printed Circular Cylinder in a Wind Tunnel*

When a cylinder is placed in a fluid of sufficiently high Reynolds number for vortices to form in the wake, vortex-induced oscillations will occur when the vortex shedding frequency approaches the natural frequency. Research on vortex-induced oscillations is motivated largely by either vibration suppression of structures such as underwater pipelines or vibration enhancement for small-scale energy harvesting. In this work, we analyze the vortex-induced oscillations of a 3D printed circular cylinder of high structure-to-fluid mass ratio (m^*) in an open circuit wind tunnel. The cylinder is mounted horizontally with four springs that can be replaced to change the spring constant (k). We consider a mass ratio of 108 and a moderate Re range of 103-104 to determine the lock-in range for different values of k. We also look for the presence of hysteresis, which has been found in previous studies on vortex-induced vibrations. Additionally, we explore the relationship between vortex shedding frequency, natural frequency, and frequency of oscillation. Using MATLAB’s image processing toolbox, our results indicate a peak non-dimensional response (A^*) of 0.8 at a reduced velocity (V_r = U/(f_nD)) of 6.7.