Vortex shedding and hovering of a rigid body in an oscillating flow

TL;DR

This study demonstrates how asymmetric rigid bodies can hover in oscillating flows by shedding vortices, revealing mechanisms of vortex-induced stability and propulsion in unsteady fluid environments.

Contribution

It introduces the concept of vortex shedding enabling asymmetric bodies to hover and move in oscillating flows, with visual evidence of vortex dynamics.

Findings

Asymmetric bodies can hover in zero-mean oscillating flows.

Vortex shedding enables the ratcheting motion of the body.

Stable hovering occurs at sufficiently high peak flow speeds.

Abstract

The fluid dynamics video shows rigid, spatially asymmetric bodies interacting with oscillating background flows. A free rigid object, here a hollow "pyramid," can hover quite stably against gravity in the oscillating airflow with a zero mean, when its peak speed is sufficiently high. We further show in shadowgraph imaging how this asymmetric body sheds vortices in such an unsteady flow, thus enabling the body to "ratchet" itself through the background flow.