An investigation of aerodynamic characteristics of leading-edge jet and trailing-edge suction set in the bridge main girder

In this study, to improve the aerodynamic performance, an experiment was performed to determine the flow structure characteristics and fluctuating aerodynamics of a bridge single-box girder model (SBGM) using leading-edge jet and trailing-edge suction (LJTS). The strength of the LJTS can be quantified using the non-dimensional jet/suction momentum coefficient (J_sj). A digital surface pressure sensor array apparatus was used to measure the external pressure distribution on the surface of the SBGM with and without LJTS. According to the results for surface pressure, the aerodynamic coefficients exerted on the SBGM were calculated through the integration of the external pressure, indicating that the fluctuating aerodynamic force decreased, and there was an optimal J_sj to achieve the best control effectiveness. In addition to the surface pressure measurement experiment, high-frequency particle image velocimetry was adopted to obtain a significant flow field surrounding the SBGM to reveal the control mechanism of the LJTS. The results for the two vertical target planes and the horizontal plane showed that the flow structure exhibited an obvious three-dimensional feature. The deficit in the streamwise velocity in the near wake of the uncontrolled case was larger, and it recovered faster than that of the controlled case, indicating that the unsteady flow was pushed further downstream by the LJTS. The proper orthogonal decomposition (POD) algorithm was utilized to divide a vortex shedding period into four phases to exhibit the dynamic variation in the flow patterns behind the experimental model. The POD mode was significantly altered in the control group. Moreover, trailing-edge suction has a significant impact on the LJTS in controlling the fluctuating aerodynamics exerted on the SBGM.