Reduced-order spanwise layout estimation of active suction-blowing jets for VIV suppression of π-shaped main girder cable-stayed bridges

Owing to its bluff-body aerodynamics characteristics, the π-shaped main girder of cable-stayed bridges is susceptible to vortex-induced vibrations (VIV). Conventional passive aerodynamic countermeasures for VIV are highly sensitive to geometric dimensions, rely on fixed installation configurations, and lack universality. These measures cannot be adjusted in real time to match the actual flow-field characteristics and modal responses of the bridge, resulting in suboptimal or ineffective vibration control. Active flow control using suction and blowing jets can be adaptively regulated in response to real-time bridge dynamics. This approach shows great potential for effectively suppressing wind-induced vibrations of bridges. This study proposes an optimization method for the spanwise layout of suction and blowing jets to improve the deployment efficiency and engineering practicality. Through sectional model wind tunnel tests and numerical simulations, two vertical VIV response ranges of the π-shaped main girder of the cable-stayed bridge were identified at attack angles of ±3 and 0°. Taking the 0° attack angle as an example, comparative case studies identified an effective control strategy—suction at the lower front side of the I-beam and blowing jet at the lower rear edge—at the reduced control wind speed of U r = U /( f h ·D ) = 23.12. The results show that this control scheme can effectively suppress the vertical VIV of the bridge. A new nonlinear vortex-induced force (VIF) model was established. An optimization approach for the minimal active-control layout, constrained to maintain positive system damping, was proposed. Results indicate that deploying control devices only in the region of strongest modal response (297 - 415 m, 16.5% of total bridge length) can effectively suppress VIV over the entire lock-in range.