Vortex shedding patterns, their competition, and chaos in flow past inline oscillating rectangular cylinders

TL;DR

This study numerically investigates vortex shedding, mode competition, and chaos in flow past inline oscillating rectangular cylinders, revealing new symmetric modes and chaotic transitions driven by mode competition.

Contribution

It introduces a new symmetric vortex shedding mode (S-III) and demonstrates chaos arising from mode competition at higher oscillation amplitudes.

Findings

Discovery of a new symmetric vortex mode S-III.

Identification of chaotic flow regimes at high amplitudes.

Chaos results from competition between symmetric and antisymmetric modes.

Abstract

The flow past inline oscillating rectangular cylinders is studied numerically at a Reynolds number representative of two-dimensional flow. A symmetric mode, known as S-II, consisting of a pair of oppositely-signed vortices on each side, observed recently in experiments, is obtained computationally. A new symmetric mode, named here as S-III, is also found. At low oscillation amplitudes, the vortex shedding pattern transitions from antisymmetric to symmetric smoothly via a regime of intermediate phase. At higher amplitudes, this intermediate regime is chaotic. The finding of chaos extends and complements the recent work of Perdikaris et al. [1]. Moreover it shows that the chaos results from a competition between antisymmetric and symmetric shedding modes. Rectangular cylinders rather than square are seen to facilitate these observations. A global, and very reliable, measure is used to establish the existence of chaos.