Two tandem cables are frequently employed as one group of hangers in a long-span suspension bridge; however, if they are close to each other, the mutual interaction between their flow fields is prone to produce large wind/wake-induced vibrations. In the present study, initially, a numerical simulation was conducted to investigate the interaction between two static tandem cable models with different spacing ratios, SR (center-to-center longitudinal spacing divided by the cable diameter, i.e. L/D). Concurrently, the passive-suction-jet control method was employed to eliminate the interaction of these two tandem cables. Aerodynamic coefficients and time-averaged and instantaneous flow fields were used to evaluate the effectiveness of the passive-suction-jet control. Subsequently, the passive-suction-jet control method was employed in a wind tunnel experiment to manipulate the wind-induced vibrations of two elastically mounted cable models. The flow patterns of the controlled tandem cables were subdivided into three basic regimes in the present study. Furthermore, the aerodynamics force suppression mechanism was explained based on the flow patterns. Both the aerodynamic forces and vibration responses of the tandem cable models reduced significantly when SR > SRc (critical spacing ratio). Particularly for SR = 4.0, the lift fluctuation reduction of both the cable models was remarkable, the fluctuating lifts of the upstream and downstream cable models decreased by 93.3% and 72.1%, respectively, and the vortex-induced vibration responses decreased by 31.4% and 54.0% respectively. Furthermore, the wake-induced vibration responses of the tandem cable models could be completely suppressed when both were controlled using passive-suction-jet pipes.
