wake-induced vibration of two cylinders with time-varying gap distances

The flow-induced vibration of an elliptical cylinder in the wake of a moving circular cylinder with time-varying gap distances was experimentally investigated. A time-resolved particle image velocimetry was used to characterize the wake dynamics and vibrations of elliptical cylinder across various initial gap distances and upstream cylinder moving speeds. Results show that after the movement of upstream cylinder, the time-series of downstream cylinder vibration can be divided into two regions. In the first region, the vibration patterns remain almost the same as those with constant gaps due to the time required for wake transport. In the second region, the vibration intensity gradually decreases with time, where the decaying rate increases with the upstream cylinder moving speed and decreases with the initial gap distances. Considering the time-varying vorticity magnitudes impinging the elliptical cylinder, a theoretical framework is applied to predict its vibrations across time. The uncovered wake-induced-vibration patterns with time-varying gap distances provide insights to understand the fluid-structure interaction mechanisms within unsteady flow environments.