This experimental study examines the flow control efficacy of symmetric synthetic jets (SSJs) on a circular cylinder wake at \(Re=2000\) , employing particle image velocimetry (PIV) to quantify wake characteristic, vortex dynamics and turbulent statistics. The SSJs, strategically positioned at the time-averaged flow separation points ( \(\theta =\pm 90^{\circ }\) ) with momentum coefficient \(C_\mu =1.34\) , which corresponds to the SSJs Reynolds number \(Re_{\overline{u_0}}=95\) , are frequency-modulated across three dimensionless actuation frequencies ( \(f_{\text {sj}}^*=f_{\text {sj}}/f_0=\) 1, 2 and 3). Results demonstrate that frequency-tuned momentum injection alters the wake structure through three frequency-dependent effects: The shedding pattern changes from 2 S to 2P; the near-wake recirculation and stagnation zones shrink; and vorticity is more confined near the cylinder, reducing downstream fluctuations. Lagrangian coherent structure (LCS) analysis shows that repelling LCSs move closer to the cylinder, while attracting LCSs converge toward \(y=0\) , consistent with a narrower wake. Reduction of the near-wake stagnation zone and recirculation region sizes indicates a progressive suppression as the SJs actuation frequency increases. Vorticity confinement in the immediate cylinder wake suppresses large-scale vortex development while promoting earlier roll-up near the cylinder and lowering velocity fluctuations downstream. The study establishes frequency-modulated SSJs as an analysis tool for multiscale wake control, offering two practical effects: stronger local mixing and weaker large-scale unsteadiness. These findings provide new insights into bluff body flow control strategies and their implications for regulating aerodynamic forces.
