Wake-induced vibration analysis for tandem cylinders with a spacing ratio of 2.5–10

The response of the tandem cylinders to flow-induced vibration related to the space ratio and flow parameters has been studied showing some of the interactions between the cylinder’s wakes; however, the interaction between perturbations from the first cylinder on the second cylinder vibration in high reduced velocities is not directly explored. Interest in analyzing this relation, the flow-induced vibration of cylinders in a tandem arrangement is experimentally investigated with the first cylinder rigidly mounted inside the aerodynamic channel, while the second one is free to vibrate transversally to the main flow. The space ratio, L/D, between the cylinders ranged from 2.5 to 10. Hotwire, microphone, and accelerometer were the experimental tools applied. The Reynolds number obtained with the tube diameter and the main flow velocity ranged from 1.12\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1.12$$\end{document} to 2.29×104\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$2.29 \times 10^{4}$$\end{document}. Cross-correlations, Fourier transform, wavelet transform, and wavelet coherence were applied to analyze the acceleration results as well as velocity and pressure fluctuations. Flow visualization in a water channel was executed to support the measurements. Results showed the increase in the acceleration of the cylinder free to vibrate with the increase in space ratios, L/D=5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$L/D = 5$$\end{document} and L/D=8\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$L/D = 8$$\end{document}. The wake from the first cylinder perturbs the second cylinder even for large pitch ratios but with a range of higher influence. The frequency analysis shows two Strouhal numbers linked to both cylinders' vortex shedding; in the coherence analysis, this influence is linked to the perturbed velocity flow between the cylinders. In the time–frequency analysis, it is observed that the levels of energy are higher for L/D = 5 and L/D = 8, and that is due to the first cylinder vortex shedding eddies strength affecting the flow in the region between the cylinders.