Wake characteristic and hanger vibration suppression by synthetic jets at the bridge tower corners

Abstract

Suspension bridge hangers are prone to severe oscillations in the wake of bridge tower. This study numerically investigated the control effect on the flow characteristics around the bridge tower and the vibration behavior of the hanger by using the synthetic jet, and further analyzed the flow control mechanism through dynamic mode decomposition (DMD) method. The results indicate that for the tower, the wake characteristic changed from alternating vortex shedding to parallel vortex streets, the aerodynamic frequencies were completely dominated by the jet excitation frequency and its harmonics, the lift fluctuation was greatly controlled due to the symmetric distribution of the disturbance forces, and the control efficiency for the hanger vibration was significantly increased to over 90%. However, for higher excitation frequencies 5 and 10, the alternating vortices recovered and the regulatory effect weakened. Moreover, the main DMD modes exhibited obvious broadband characteristics, and its flow field exhibited symmetrical distribution. The vibration suppression mechanism first lies in the fact that the change in the wake pattern reduces the fluctuating characteristics of the flow field. Meanwhile, the frequencies of the main modes of the flow field deviate significantly from the natural frequency of the hanger, making it difficult to induce severe oscillation.