Effect of elastic coupling on flow-induced vibration (FIV) of elastically mounted tandem cylinders.*

The flow-induced vibration (FIV) of elastically coupled tandem cylinders is useful in modeling many engineering applications such as overbridges between buildings, structural connections between parallel tubes and pipelines, connected offshore wind turbines, twin bridge connections, etc. While there are several studies on FIV of uncoupled tandem cylinders, there is no study on the coupled system, to our knowledge. Using numerical simulations at low Reynolds number (Re=100), we present the FIV response of the cylinders for a wide range of gap ratios (1.1-5) and reduced velocities (4-18). The stationary tandem cylinder configuration can result in six possible flow structures, while the elastically coupled cylinders exhibit two possible mode shapes (in-phase and out-of-phase). Consequently, ten FIV regimes result from a combined flow and elastic coupling between the cylinders.

Our results suggest that the same system with an identical mass ratio can be tuned for FIV suppression or energy harvesting. The in-phase mode limits the upstream cylinder amplitude below 0.3 for the considered range of reduced velocity and gap ratio, without adding any damping. Similarly, the out-of-phase mode shows a higher energy harvesting potential for a single energy harvesting unit than two on the classic uncoupled tandem cylinder configuration.