Suppression of Vortex-Induced Vibration of Π-Type Girder Cable-Stayed Bridges Using Active Suction/Blowing Jets

Due to its bluff body characteristics, the [Formula: see text]-shaped girder section of cable-stayed bridges is highly prone to vortex-induced vibrations (VIV). To achieve active flow control for VIV mitigation of girders, this study investigates suction and blowing jet flow control of VIV on a [Formula: see text]-shaped girder, based on sectional model wind tunnel tests and numerical simulations using dynamic mesh methods. The mechanisms of the two VIV regions in the [Formula: see text]-shaped girder are analyzed through vorticity contours. Eight suction/blowing configurations were systematically designed. The effectiveness of each control scheme was evaluated by comparing vertical displacement responses, aerodynamic parameters, and flow field characteristics. Results indicate two distinct VIV regions in the [Formula: see text]-shaped girder. The first region results from periodic simultaneous vortex shedding in the wake, whereas the second stems from alternating shedding of vortices convected from front to rear. Among the eight control schemes, the upstream I-girder lower flange bottom forward suction schemes (S-I, S-II, S-III) and a combined scheme with forward suction upstream and backward blowing downstream (SB-II) significantly reduce the root mean square lift coefficient. The former slightly increases the mean drag coefficient, while the latter shows a non-monotonic trend: first decreasing, then increasing. At a dimensionless control flow rate of [Formula: see text], the upstream I-girder lower flange horizontal forward suction scheme (S-II) achieves optimal suppression of the second VIV region while showing no significant effect on the first VIV region. In contrast, the combined upstream I-girder lower flange horizontal forward suction with downstream I-girder lower flange backward blowing scheme (SB-II) demonstrates complete suppression of both VIV regions. At [Formula: see text], the downstream I-girder lower flange backward-facing suction scheme (S-II-R) achieves complete suppression of the first VIV region while exhibiting an amplifying effect on vibration amplitudes within the second VIV region. With proper pipe placement and control parameter tuning, VIV under reduced velocity [Formula: see text] can be fully suppressed at [Formula: see text].