Vortex and wake-induced vibrations of a circular cylinder pendulum

An experimental investigation of vortex- and wake-induced vibrations of a circular cylinder pendulum in cross-flow is presented. The study considers a tandem configuration in which a pendulum-mounted cylinder is immersed in the wake of a stationary upstream cylinder, introducing a rotational degree of freedom distinct from classical translational systems. The isolated pendulum exhibits typical vortex-induced vibration features, including response branches and frequency lock-in. Under wake interference, oscillation amplitudes increase monotonically with reduced velocity, with the strongest response at the smallest spacing ratio. Wake forcing also reduces the oscillation frequency and shifts the transition to the out-of-phase regime toward higher reduced velocities.