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Three dimensional structure of the unsteady wake of an axisymmetric body

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posted on 05.03.2019 by Giancarlo Pavia, Max Varney, Martin Passmore, Mathew T. Almond
The near-wake of an axisymmetric body has been investigated using base pressure tappings and 4 large scale Tomographic Particle Image Velocimetry (TPIV) at a Reynolds number of ReD = 5 3.2 × 105 , based upon model diameter. Insights into the near-wake dynamics are provided by the 6 application of Proper Orthogonal Decomposition (POD) to the pressure and the TPIV datasets. 7 The first two POD modes show that the axisymmetric topology seen in the time averaged field is 8 the result of the combination of different reflectional symmetry preserving states, each one featuring 9 a hairpin vortex surrounded by an annular structure developing in proximity to the wake closure. 10 The ‘head’ and the ‘tails’ of each hairpin vortex appear to be dynamically linked, as also proven by 11 the existence a second pair of modes, visible only in the TPIV dataset, featuring a twisted two-lobe 12 structure. The analysis of the temporal evolution of the radial position of the centre of pressure over 13 the model base reveals the existence of two different low-drag scenarios, characterised respectively 14 by the restoration of the axial symmetry or the selection of a single plane of reflectional symmetry. 15 The first state is reported to become the only admissible low-drag configuration when the short-time 16 wake dynamics are removed from the unsteady pressure signal.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Aeronautical and Automotive Engineering

Published in

Physics of Fluids

Volume

31

Issue

2

Citation

PAVIA, G. ... et al., 2019. Three dimensional structure of the unsteady wake of an axisymmetric body. Physics of Fluids, 31: 025113.

Publisher

© The Authors. Published by AIP Publishing

Version

VoR (Version of Record)

Publisher statement

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in PAVIA, G. ... et al., 2019. Three dimensional structure of the unsteady wake of an axisymmetric body. Physics of Fluids, 31: 025113. and may be found at https://doi.org/10.1063/1.5078379

Acceptance date

30/01/2019

Publication date

2019-02-19

ISSN

1070-6631

eISSN

1089-7666

Language

en

Article number

025113

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