| Popis: |
Lower aspect ratio cylinders are of interest as these are used for, e.g., wind turbine towers. We present a study predicting the vortex-induced vibration (VIV) characteristics of a cantilever circular cylinder with an aspect ratio (length-to-diameter ratio) of 10. The free end condition caused tip vortices to generate end-cell-induced vibration (ECIV) occurring at wind speeds higher than the threshold wind speed for VIV. Wind tunnel experiments were conducted at Reynolds numbers ranging from 3.6 × 104 to 3.26 × 105. The cantilever circular cylinder was made of a polypropylene pipe mounted on a six-degree-of-freedom load cell. Its upper end was free to oscillate in the streamline and transverse directions. An accelerometer was placed at the top of the cylinder to measure accelerations and, via twofold integration, retrieve cylinder motions at its free end. Down-wash tip vortices occurred. The response amplitude with vortex shedding was finite, even at the synchronization point. It increased with flow velocity and affected the synchronization behavior. Results suggested that nonlinearities occurring when vortices were Shedd were due to free end conditions and higher Reynolds numbers. |
