Multi-mode responses, rivulet dynamics, flow structures and mechanism of rain-wind induced vibrations of a flexible cable

We successfully excite the multi-mode rain-wind induced vibrations (RWIVs) of a flexible stay cable in a wind tunnel by guiding water rivulets along the cable surface. The first, second and third mode RWIVs are excited respectively by increasing the incoming wind speed. The movement of upper rivulet during the first, second and third mode RWIVs are recorded with a high-speed camera. By employing a computer vision based recognition technique, the upper-rivulet dynamics of different modes of RWIVs are recognized and analyzed. The wake flow structures around the dry cable and the cable suffering from RWIVs are measured by using a particle image velocimetry (PIV) system. Experiment results show that the oscillation frequency of the upper rivulet is synchronized with the cable vibration frequency for the first, second and third mode RWIVs. Based on experiment results, bubble burst is proposed as a possible mechanism for the excitation of RWIVs.