Pavia_1.5078379.pdf (14.81 MB)
Three dimensional structure of the unsteady wake of an axisymmetric body
journal contribution
posted on 2019-03-05, 10:55 authored by Giancarlo Pavia, Max Varney, Martin Passmore, Mathew T. AlmondThe 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 FluidsVolume
31Issue
2Citation
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 PublishingVersion
- 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/10.1063/1.5078379Acceptance date
2019-01-30Publication date
2019-02-19ISSN
1070-6631eISSN
1089-7666Publisher version
Language
- en