Abstract
This paper presents an exploratory analysis of the oscillation process of a set of two circular cylinders (D = 25 mm) mounted with a fixed pitch-to-diameter ratio P/D = 1.26 and attached to a free-to-rotate circular table submitted to a turbulent crossflow in a wind tunnel. Measurements were performed with hot wire anemometers placed in the wake of the cylinders synchronized with a high-speed digital camera. Flow visualizations with static cylinders in a water channel were performed to investigate the wake formation around the cylinders. The analysis of the results was made through Fourier and wavelet transforms. The main objective is to address the observed phenomenon with its causing physical mechanism. Wind tunnel results showed that, depending on the imposed mean flow velocity, the set starts oscillating with a low steady amplitude. When the flow is disturbed, an increase in the oscillation amplitude is observed, remaining in this steady regime even after removing the disturbance. Although the interaction between the flow and cylinder set generates two stable states, the properties of the oscillation phenomena (frequency and amplitude) remained the same, pointing out an intrinsic property of the dynamical system. The vortex shedding is identified to be the primary mechanism responsible for initiating the small amplitude oscillation, while the flow passing through the gap between the cylinders is the cause of the high amplitude oscillation. The flow visualization corroborated the wake analysis described in the wind tunnel experiments. No evidence of coherence between the vortex shedding from the first cylinder and the oscillation process was identified. Considering the results in the present work, the configuration analyzed may work as a vortex-shedding suppressor.
Published Version
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