Mitigation of unsteady aerodynamic force of bridge main girder via serrated leading and trailing edges

In this study, the aerodynamic coefficient and wake flow behind a bridge main girder model (BMGM) with and without serrated leading and trailing edges are investigated. Serrated structures are individually set on both edges of the main girder to create disturbances in the flow structure, thus modifying the flow field around the BMGM and reducing the fluctuating aerodynamic forces exerting on the main girder. Based on the incoming flow velocity and BMGM height, the Reynolds number is estimated to be 2.3 × 10⁴. A digital surface pressure scanner is used to record the outer-surface pressure around the BMGM. The aerodynamic coefficients exerted on the BMGM are estimated from pressure measurements. The results indicate that the applied control method alters the outer-surface pressure amplitude and reduces both the mean and unsteady values of the aerodynamic coefficients. In addition to investigating the outer-surface pressure, two-dimensional particle image velocimetry is employed to capture the characteristics of fluid dynamics behind the BMGM and investigate the control mechanism contributing to reduced aerodynamic forces. Additionally, orthogonal decomposition is utilized to isolate the significant and main flow structures, thus revealing the wake vortex patterns. The secondary instability of streamwise vortices is analyzed to understand the underlying control mechanism of the serrated structures.