Wind tunnel experiments on flow-induced vibration and energy harvesting: Vibrating and stationary cylinder interactions

• Two tandem-cylinder configurations are experimentally studied, showing distinct vibration mechanisms in oscillation cylinders. • Stationary cylinder diameter and spacing affect vibration amplitude and the transition between lock-in and galloping regimes. • Optimal power generation conditions differ between cases, governed by geometric parameters and flow velocity. • A nonlinear wake oscillator model effectively supports the isolated-cylinder vibration behavior. This study experimentally investigates flow-induced vibrations and energy harvesting in tandem circular cylinders under two configurations: an upstream vibrating cylinder with a stationary downstream cylinder, and a downstream vibrating cylinder placed in the wake of a stationary upstream cylinder. Displacement amplitudes were measured using high-speed imaging, while electrical output was obtained through a piezoelectric transducer. In Case 1, where the upstream cylinder vibrates, the presence of a downstream stationary cylinder substantially increases vibration levels, especially for larger stationary-cylinder diameters. At S = 4 c m , the maximum displacement amplitudes occur for D 2 = 5 c m , with increases of 84% and 25% when increasing the stationary-cylinder diameter from 3 to 4 cm and 4 to 5 cm, respectively. Compared to the isolated cylinder (peak amplitude at U = 6.5 m / s ), the vibrating upstream cylinder exhibits increases of 56% and 96% for D = 4 and D = 5 c m , respectively. Optimal power generation in Case 1 is achieved at S = 4 c m , D 2 = 4 c m , and flow velocities of 6 − 8 m / s . In Case 2, where the downstream cylinder vibrates in the wake of an upstream stationary cylinder, galloping and wake-induced vibration dominate the response. The strongest amplification occurs for D 1 = 3 cm at S = 8 c m , where displacement amplitudes rise sharply with increasing flow velocity, exhibiting an 88% increase relative to the isolated cylinder at low velocities and up to 114% at higher velocities. Voltage and power outputs similarly peak at S = 8 c m , particularly for the smallest upstream-cylinder diameter.