Identification of large coherent structures in supersonic axisymmetric wakes
Identification of large coherent structures in supersonic axisymmetric wakes
Direct numerical simulation data of supersonic axisymmetric wakes are analysed for the existence of
large coherent structures. Wakes at Ma ¼ 2:46 are considered with results being presented for cases at
Reynolds numbers ReD ¼ 30; 000 and 100,000. Criteria for identification of coherent structures in freeshear
flows found in the literature are compiled and discussed, and the role of compressibility is
addressed. In particular, the ability and reliability of visualisation techniques intended for incompressible
shear-flows to educe meaningful structures in supersonic wakes is scrutinised. It is shown that some of
these methods retain their usefulness for identification of vortical structures as long as the swirling rate is
larger than the local compression and expansion rates in the flow field. As a measure for the validity of
this condition in a given flow the ‘vortex compressibility parameter’ is proposed which is derived here.
Best ‘visibility’ of coherent structures is achieved by employing visualisation techniques and proper
orthogonal decomposition in combination with the introduction of artificial perturbations (forcing of
the wake). The existence of both helical and longitudinal structures in the shear layer and of hairpin-like
structures in the developing wake is demonstrated. In addition, elongated tubes of streamwise vorticity
are observed to emanate from the region of recirculating flow
1638-1650
von Terzi, D.A.
d9369e9f-b41d-403d-a898-84968542a33b
Sandberg, R.D.
41d03f60-5d12-4f2d-a40a-8ff89ef01cfa
Fasel, H.F.
45db4ae8-5501-4afd-9d6f-b35ac55e7629
September 2009
von Terzi, D.A.
d9369e9f-b41d-403d-a898-84968542a33b
Sandberg, R.D.
41d03f60-5d12-4f2d-a40a-8ff89ef01cfa
Fasel, H.F.
45db4ae8-5501-4afd-9d6f-b35ac55e7629
von Terzi, D.A., Sandberg, R.D. and Fasel, H.F.
(2009)
Identification of large coherent structures in supersonic axisymmetric wakes.
Computers & Fluids, 38 (8), .
(doi:10.1016/j.compfluid.2009.01.007).
Abstract
Direct numerical simulation data of supersonic axisymmetric wakes are analysed for the existence of
large coherent structures. Wakes at Ma ¼ 2:46 are considered with results being presented for cases at
Reynolds numbers ReD ¼ 30; 000 and 100,000. Criteria for identification of coherent structures in freeshear
flows found in the literature are compiled and discussed, and the role of compressibility is
addressed. In particular, the ability and reliability of visualisation techniques intended for incompressible
shear-flows to educe meaningful structures in supersonic wakes is scrutinised. It is shown that some of
these methods retain their usefulness for identification of vortical structures as long as the swirling rate is
larger than the local compression and expansion rates in the flow field. As a measure for the validity of
this condition in a given flow the ‘vortex compressibility parameter’ is proposed which is derived here.
Best ‘visibility’ of coherent structures is achieved by employing visualisation techniques and proper
orthogonal decomposition in combination with the introduction of artificial perturbations (forcing of
the wake). The existence of both helical and longitudinal structures in the shear layer and of hairpin-like
structures in the developing wake is demonstrated. In addition, elongated tubes of streamwise vorticity
are observed to emanate from the region of recirculating flow
Text
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- Accepted Manuscript
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Published date: September 2009
Identifiers
Local EPrints ID: 71898
URI: http://eprints.soton.ac.uk/id/eprint/71898
ISSN: 0045-7930
PURE UUID: 3ee17f0b-186a-401a-b150-808573e937be
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Date deposited: 12 Jan 2010
Last modified: 13 Mar 2024 20:50
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Author:
D.A. von Terzi
Author:
R.D. Sandberg
Author:
H.F. Fasel
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