Numerical simulation study of vortex-induced vibration suppression for two tandem circular cylinders based on synthetic jets

The two tandem cylinders generate significantly larger vortex-induced vibration (VIV) responses and exhibit more complex fluid–structure interactions under identical flow conditions, thereby accelerating fatigue damage accumulation and compromising structural integrity. In this study, the hydrodynamic and flow dynamic characteristics of two tandem cylinders were numerically examined. The effects of jet position, momentum coefficient (Cμ), and dimensionless frequency (fsj*) on the VIV suppression of the downstream cylinder were systematically investigated. The Reynolds number (Re = ρUD/μ, where ρ, U, D, and μ are the fluid density, incoming velocity, diameter of the cylinder, and dynamic viscosity of water) was fixed at 150. The distance ratio (L/D, where L is the center-to-center distance between two cylinders) was 3. The results demonstrate that the effectiveness of VIV suppression is highly dependent on the jet actuation position. Suboptimal suppression is observed when the jet is applied at the separation points or on the upper and lower sides of the cylinder, whereas optimal performance is achieved when actuation occurs at the front and rear stagnation points. Cμ and fsj* also exhibit significant influences on the control effectiveness. The synthetic jet control achieves maximal suppression of VIV at Cμ = 4 and fsj* = 8, attaining 56% reduction in vibration amplitude, 98% mean drag reduction, and 37% attenuation of lift fluctuation. This optimal control strategy demonstrates robust performance across L/D of 2–6, maintaining significant vibration amplitude suppression, and exhibiting broad applicability for engineering structures. These findings offer practical insights into vibration control for a wide range of slender structures subjected to fluid-structure interactions, including chimneys, offshore risers, and bridge stay cables.