Wake-vortex evolution behind a fixed circular cylinder with symmetric jets

In this study, we investigated the wake-vortex dynamics behind a circular cylinder with an active symmetric jet control on its leeward surface by using high-speed particle image velocimetry (PIV) via wind tunnel tests. The experimental investigations were performed at a Reynolds number (Re) of 3.33 ×10⁴. Steady slot jets were acted symmetrically into the near-wake region from the leeward surface of the cylindrical model. The azimuthal position of the slot jets was varied from 0°to 90°from the center-line. The proper orthogonal decomposition (POD) method was used as a tool to study the effect of modifications of active jets on the periodic vortex shedding and their dynamic interactions in the cylinder wake. Both dynamic evolutions and time-averaged results in the near-wake region were presented and analyzed to demonstrate the control effects of the symmetric jets. The experimental results indicated that the unsteady wakes of the cylinder were stabilized and attenuated when the azimuthal angle of the jets was set to 0°and 90°, whereas for other azimuthal angles, the symmetric jets were oblique to the sheared layers and their control effects were limited.