The effects of pulsed blowing jets on power gain of vortex-induced vibrations of a circular cylinder

Abstract

To enhance the power gain of vortex-induced vibration of a circular cylinder, the active control method of pulsed blowing jets located at θ = 90° is utilized to intensify its oscillation with the two-dimensional simulation of Reynolds-averaged Navier–Stokes at 2.0 × 104 ≤ Re ≤ 9.6 × 104. Different from traditional continuous jets, the blowing jets used in this paper start once the cylinder moves to the upper limited position and last for a certain duration. Based on the combination of nine momentum coefficients and four pulse durations of the jets, the oscillation responses of the cylinder at a series of reduced velocities are calculated and distinct responses are observed in three branches. In the initial branch (U* ≤ 4.27), no matter what the values of Cμ and n are, the vortex patterns keep 2S accompanied by the amplitude ratios vibrating around the benchmarks. In the fore part of the upper branch (4.27 < U* ≤ 6.17), as Cμ ≤ 0.1005, the control effect is similar to that at U* ≤ 4.27; as Cμ > 0.1005, both slight enhancement and suppression in amplitude ratios are observed, as well as the small values of power gain ratios. In the rear part of the upper branch and lower branch (U* > 6.17), the enlarged disturbance of the jets to wake results in enhanced amplitude ratios for most cases. Galloping is observed at n = 1/4 and 1/2 with a maximum amplitude ratio 13 times the benchmark, except for some suppressed cases at Cμ > 0.1005, n = 1/16, and 1/8. Though large amplitude ratios are achieved, considering more energy consumed as Cμ increases, the better control strategy with η ranging from 5.45% to 19.78% falls in U* > 6.17 and Cμ < 0.1005.