The Vortex Ring State of a Shrouded Rotor

Pickles, D.J., Zagaglia, D. , Green, R.B. and Busse, A. (2021) The Vortex Ring State of a Shrouded Rotor. 47th European Rotorcraft Forum, 07-09 Sep 2021.

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Abstract

An experimental investigation into the flow field produced by a shrouded rotor, operating in axial descent is presented. Laser Doppler Anemometry (LDA) was used to determine the induced velocity of the rotors, whilst Particle Image Velocimetry (PIV) was applied to investigate the dynamics of the unsteady flow field produced. Tests were repeated using the same rotor, without the shroud, to assess its influence on the observed phenomena. At low descent velocity ratios, the mean flow field resembled that produced by a shrouded rotor operating in hover. At slightly higher descent velocity ratios, the wake from the shrouded rotor broke down, leading to the formation of a large region of recirculation outboard of the shroud which aperiodically sheds into the free stream. Further increases in descent velocity lead the centre of recirculation to form around the external surface of the shroud. The flow topology appears to be generally similar to the one arising from an isolated rotor operating in descent flight, however the results suggest that the presence of the shroud might slightly delay the onset of the Vortex Ring State (VRS).

Item Type:Conference or Workshop Item
Keywords:Rotorcraft, shroud, aerodynamics, vortex ring state, particle image velocimetry (PIV), laser doppler anemometry (LDA), wind tunnel.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Busse, Dr Angela and Green, Dr Richard and Pickles, Mr David and Zagaglia, Dr Daniele
Authors: Pickles, D.J., Zagaglia, D., Green, R.B., and Busse, A.
College/School:College of Science and Engineering > School of Engineering > Aerospace Sciences
Copyright Holders:Copyright © 2021 The Authors
First Published:First published in 47th European Rotorcraft Forum: 110
Publisher Policy:Reproduced under a Creative Commons License
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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 - Aerospace Sciences