Wake control based on spanwise sinusoidal perturbations

The effectiveness of a passive sinusoidal perturbation method, applied oil the upstream faces of square cylinders at a wavelength that corresponds to the wavelength of the intermediate wake instability mode, is experimentally investigated. Hot-wire measurements are taken to examine the effect of three different sinusoidal perturbation amplitudes as compared to the straight cylinder case. Good agreement is found between high- and low-Reynolds-number results, suggesting that the main flow dynamics features, as well as the flow control method efficiency, are Reynolds independent. Two sets of measurements are taken: in the near and in the intermediate to far wake. The near-wake measurements show that the method is very effective in mitigating the von Karman vortices as previously found, whereas the intermediate to far wake measurements indicate that the wake decay is accelerated by the sinusoidal perturbations, therefore, being beneficial in the reduction of wake aeroelastic instabilities.