Numerical analysis of reverse wake-induced vibration at low Reynolds number.

Reverse wake-induced vibration (RWIV) of two tandem cylinders with the downstream one fixed is numerically studied in this paper; Reynolds number is set as 150 (Re = 150). The effect of different spacing ratios (α) ranging from 3 to 6 with a gap of 0.5 is simulated to investigate the vibration characteristics of RWIV, where the spacing ratio (α) is defined as the nondimensional ratio of the center-to-center separation between the cylinders. As the spacing ratio increases from 3 to 6, RWIV shows a transition from galloping to vortex-induced vibration (VIV), which is also a reverse phenomenon compared to wake-induced vibration (WIV). As to the wake mode, two different types of vortex motion (2S - 2P - 2S and 2S - 2P) are observed within the given range of spacing ratio. Empirical modal decomposition is also applied to further analyze the vibration characteristics of galloping and VIV in RWIV. When the system shows galloping, the number of decomposed modes is larger with the increasing reduced velocity, and different vibration modes show evident mutual anisotropy. In addition, the vortex line diagram is used to analyze the wake vortex characteristics of the RWIV and to supplement the above findings. [ABSTRACT FROM AUTHOR]