Numerical investigation on the suppression of vortex-induced vibration system by assembling different rotors based on quasi-active control method

Combining the innovative concept of quasi-active control method, a numerical simulation is conducted to investigate the vortex-induced vibration (VIV) responses. The objects of this study include a main cylinder (MC) and a cylindrical system outfitted with a pair of rotors of different types (with Banki rotors, Darrieus rotors, and Savonius rotors, denoted as WBR, WDR, and WSR), and the VIV responses are analyzed within the Reynolds number range of 0.8 × 10³≤Re ≤ 5.6 × 10³. The findings indicate that all three kinds of rotors show excellent vibration suppression effect in downstream and cross-flow directions by adjusting the VIV response (amplitude, frequency, hydrodynamic coefficient) and vortex pattern (vortex mode, wake shape). The maximum amplitude suppression rate can reach 99% for the Banki and Savonius cases at high reduced velocity. Within the whole velocity range, the maximum amplitudes of WBR, WDR, and WSR cases in the downstream and cross-flow directions were 0.32 and 0.45 times, 0.73 and 0.65 times, and 0.28 and 0.33 times, respectively, compared to the maximum amplitude of MC. The time-averaged drag coefficient of the controlled cylinder in the WBR case was minimized to about 0.015. The Banki rotor and Savonius rotor significantly reduced the vibration frequency of the VIV system compared to the Darrieus rotor. Especially, the Banki rotor could keep the VIV system vibration frequency within a narrow range at different reduced velocity. Moreover, the vorticity contour of the VIV system with assembled rotors was significantly improved, with a narrower flow wake width and more regular vortex shedding at high reduced velocity. Considering both amplitude suppression and drag coefficient, Banki rotors were recommended.