MS17.2: Fluid-Structure Interaction

Initially focused on suppressing Vortex-Induced Vibrations (VIV) to mitigate their detrimental effects on engineering structures, ongoing research has shifted towards harnessing VIV for energy. Such VIV-based energy harvester can be a promising alternative to rotor-based installations in low speed water flow conditions. However, the inherent nature of VIV limits such a device to nominally function in its lock-in regime. This work suggests to broaden the nominal range by shifting the lock-in range with the help of virtual springs.

This study numerically investigates the in-line flow-induced vibration (FIV) of elastically mounted elliptical cylinders undergoing forced rotations in a free-stream flow. The two-dimensional numerical simulations were conducted at a Reynolds number of 100. The cross-sectional aspect ratio of the cylinders varied from 1 to 0.25. The dimensionless rotation rate is set from low to high at 0.2, 0.5 and 1. Amplitude and frequency response are demonstrated in detail. The results demonstrate that the in-line vibration of rotating elliptical cylinder exhibits a substantially larger amplitude than the circular cylinder, on the order of one body diameter. In general, the major peak of the amplitude occurs when the rotating frequency locks to the structural natural frequency. The vibration response typically consists of harmonics associated with rotation as well as harmonics associated with vortex shedding, and a decrease in the aspect ratio results in the FIV to transition from vortex-induced to rotation dominance, while an increase in rotation rate reduces rotation dominance in turn.

Synchronized oscillators are ubiquitous in nature and engineering. Synchronization is typically studied via a simplified model valid only in the weak coupling limit. Here, we report the first theoretical modeling and experimental observation of a synchronized pair of non-weakly coupled aeroelastic oscillators. We find remarkable quantitative agreement between the experiments and our theoretical higher-order phase model of non-weak coupling. Our study establishes that experimentally measured synchronization can be accurately predicted in non-weakly coupled systems and, therefore, serves as a call for a paradigm shift.