The vortex ring state of a rotor and its comparison with the collapse of an annular jet in counterflow

Pickles, D.J. , Green, R.B. and Busse, A. (2023) The vortex ring state of a rotor and its comparison with the collapse of an annular jet in counterflow. Physics of Fluids, 35, 044103. (doi: 10.1063/5.0143406)

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The vortex ring state (VRS) of a rotor is associated with the development of the trailed vortex system in powereddescending flight, where the topology of the vortex wake changes from its usual helical form into a toroidal form. Inthe VRS the toroidal vortex ring envelops the entire rotor, and it sheds and reforms in an unsteady manner. In previous attempts to understand the basic phenomenology of the VRS, the focus was on the role of the trailed vortices in the transition to the VRS: computational and experimental work utilised rotor models to generate the trailing vortex wake, and mechanisms for the emergence of the VRS were postulated based upon the interaction of the trailed vortices. In this paper a different approach is taken: a set of experiments on a core annular jet flow are described, where the jet flow in counterflow is used to simulate a rotor in powered descent. It is shown that this leads to the formation of a flow field that shares many of the features of the VRS of a rotor system. This brings into question the role of the rotor blade trailing vortices in the development of the rotor wake VRS, and it is proposed instead that the interaction between the mean flow and counterflow drives the VRS phenomenon.

Item Type:Articles
Additional Information:The experiments were conducted using instrumentation provided by UK National Wind Tunnel Facility supported by the UK EPSRC, grant number EP/L024888/1.
Glasgow Author(s) Enlighten ID:Busse, Dr Angela and Green, Dr Richard and Pickles, Mr David
Authors: Pickles, D.J., Green, R.B., and Busse, A.
College/School:College of Science and Engineering > School of Engineering > Autonomous Systems and Connectivity
College of Science and Engineering > School of Engineering > Systems Power and Energy
Journal Name:Physics of Fluids
Publisher:American Institute of Physics
ISSN (Online):1089-7666
Published Online:04 April 2023
Copyright Holders:Copyright © 2023 The Authors
First Published:First published in Physics of Fluids 35:044103
Publisher Policy:Reproduced under a Creative Commons licence

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
190699National Wind Tunnel FacilityFrank CotonEngineering and Physical Sciences Research Council (EPSRC)EP/L024888/1ENG - Autonomous Systems & Connectivity