Control of vortex shedding from two side-by-side cylinders using a pair of tangential jets

The active control of two side-by-side cylinder wakes by tangential jets with a Reynolds number of 3900 and a pitch ratio of 1.1 was studied experimentally and numerically. The particle image velocimetry technique was used to obtain the flow around side-by-side cylinders in a wind tunnel, and the dynamic lift on the cylinder was measured by a three-axis force-sensor. A numerical model was set up for comparison with the experimental data. The effects of the jet angles and jet intensities on the wake control were discussed. It was found that the flow structure was bistable biased flow and that the gap flow led to an asymmetry of the flow field. Tangential jets with angles smaller than 20° were ineffective in controlling the wake and suppressing the vortex-induced vibrations of the cylinders. Tangential jets with angles larger than 45° induced a reverse vortex and were not suitable to be applied. The vortex flow region became smaller with an increase in the jet momentum coefficient but needed additional power supply. A moderate jet angle of 45° with a jet momentum coefficient of 0.218 demonstrated the best control effect in which the shedding vortex could be controlled in a small triangle region behind the cylinders (X ≦ 1.5D). The peak amplitude of the cylinder lift power spectral density (PSD) can be reduced to ∼8.7% of the PSD without the control. Effective control via the use of tangential jets provides a theoretical basis for subsequent active closed-loop control.