Flow Dynamics of the Transversely Oscillating Tapered Circular Cylinder under Vortex-Induced Vibrations at low Reynolds number

TL;DR

This paper numerically examines how tapering affects flow-induced vibrations of elastically mounted circular cylinders at low Reynolds number, revealing differences in vortex shedding, wake structures, and synchronization behavior.

Contribution

It introduces a detailed analysis of the impact of taper ratios on vortex-induced vibrations and wake dynamics of cylinders, highlighting new insights into flow-structure interactions at low Reynolds numbers.

Findings

Tapering alters vortex shedding patterns and wake structures.

Tapered cylinders exhibit a wider lock-in region compared to uniform cylinders.

Taper ratio influences the amplitude response and transition behavior.

Abstract

This study numerically investigates the influence of the taper on the flow-induced vibrations of an elastically mounted circular cylinder under Vortex-induced vibrations. The dynamic response of three different taper ratios defined as 12 (highly tapered cylinder), 20 (medium tapered cylinder), and 40 (low tapered cylinder))is studied at a fixed Reynolds number, defined based on the averaged cylinder diameter, of 150. The amplitude and frequency response of the tapered cylinder is characterized by a low mass ratio (defined as the ratio of the total oscillating mass to the displaced fluid mass) = 2 over the wide range of reduced velocity covering the full amplitude-response spectrum (based on the oscillation amplitude) of the VIV. The results show the existence of difference in the spanwise shedding of vortices owing to the poor spanwise pressure correlation. The flow field analysis in the wake of the oscillating cylinder reveals the dominance of the three-dimensional structures in the wake (near the top end with the larger diameter) behind the cylinder with the increase in the taper ratio (even at such low where the uniform cylinder exhibits the two-dimensional wake). Also, the tapered cylinder exhibits a wide range of frequency synchronization (i.e. wide lock-in area) compared to the uniform cylinder. Tapering the cylinder results in the shift of the peak of the max oscillation amplitude or, in turn, the shift in the transitioning of the response branches. Further, force decomposition, energy transfer, and phase dynamics are also discussed for the taper cylinders.