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Numerical simulation of the spatiotemporal development of linear disturbances in Stokes layers: Absolute instability and the effects of high-frequency harmonics

Xander Ramage, Christopher Davies, Christian Thomas, Michael Togneri Orcid Logo

Physical Review Fluids, Volume: 5, Issue: 10

Swansea University Authors: Xander Ramage, Michael Togneri Orcid Logo

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DOI (Published version): 10.1103/physrevfluids.5.103901

Abstract

For a family of oscillatory Stokes layers, the spatiotemporal evolution of impulsively excited disturbances is investigated, using direct numerical simulations of the linearized Navier-Stokes equations. The semi-infinite planar Stokes layer is modified to incorporate a low-amplitude, high-frequency...

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Published in: Physical Review Fluids
ISSN: 2469-990X
Published: American Physical Society (APS) 2020
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URI: https://cronfa.swan.ac.uk/Record/cronfa55533
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spelling 2020-12-04T17:53:13.4260601 v2 55533 2020-10-28 Numerical simulation of the spatiotemporal development of linear disturbances in Stokes layers: Absolute instability and the effects of high-frequency harmonics 5fc043d595817fc00de1d606af37206e Xander Ramage Xander Ramage true false 7032d5a521c181cea18dbb759e1ffdeb 0000-0002-6820-1680 Michael Togneri Michael Togneri true false 2020-10-28 EEN For a family of oscillatory Stokes layers, the spatiotemporal evolution of impulsively excited disturbances is investigated, using direct numerical simulations of the linearized Navier-Stokes equations. The semi-infinite planar Stokes layer is modified to incorporate a low-amplitude, high-frequency harmonic, which provides a simplified model of the external noise found in physical experiments. For the unmodified Stokes layer, impulsively excited disturbances are known to form family-tree-like structures, composed of multiple wave packets. The long-term behavior that is encompassed within these structures is studied, together with the effects upon them of the alterations to the base flow. In the absence of any base-flow modification, the disturbances are discovered to exhibit a subharmonic pattern of temporal growth, with a periodicity that is twice that of the basic state. It is also shown that when linear instability first arises, it takes an absolute rather than a convective form. Inclusion of a high-frequency harmonic into the basic state is found to have a strong and destabilizing impact upon the impulse response. The development of the family-tree-like disturbance structure can be disrupted, changing the character of the absolute instability and promoting its appearance at much reduced Reynolds numbers. Journal Article Physical Review Fluids 5 10 American Physical Society (APS) 2469-990X 2 10 2020 2020-10-02 10.1103/physrevfluids.5.103901 http://orca.cf.ac.uk/135864/ COLLEGE NANME Engineering COLLEGE CODE EEN Swansea University 2020-12-04T17:53:13.4260601 2020-10-28T09:17:57.1114291 Faculty of Science and Engineering School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Mechanical Engineering Xander Ramage 1 Christopher Davies 2 Christian Thomas 3 Michael Togneri 0000-0002-6820-1680 4
title Numerical simulation of the spatiotemporal development of linear disturbances in Stokes layers: Absolute instability and the effects of high-frequency harmonics
spellingShingle Numerical simulation of the spatiotemporal development of linear disturbances in Stokes layers: Absolute instability and the effects of high-frequency harmonics
Xander Ramage
Michael Togneri
title_short Numerical simulation of the spatiotemporal development of linear disturbances in Stokes layers: Absolute instability and the effects of high-frequency harmonics
title_full Numerical simulation of the spatiotemporal development of linear disturbances in Stokes layers: Absolute instability and the effects of high-frequency harmonics
title_fullStr Numerical simulation of the spatiotemporal development of linear disturbances in Stokes layers: Absolute instability and the effects of high-frequency harmonics
title_full_unstemmed Numerical simulation of the spatiotemporal development of linear disturbances in Stokes layers: Absolute instability and the effects of high-frequency harmonics
title_sort Numerical simulation of the spatiotemporal development of linear disturbances in Stokes layers: Absolute instability and the effects of high-frequency harmonics
author_id_str_mv 5fc043d595817fc00de1d606af37206e
7032d5a521c181cea18dbb759e1ffdeb
author_id_fullname_str_mv 5fc043d595817fc00de1d606af37206e_***_Xander Ramage
7032d5a521c181cea18dbb759e1ffdeb_***_Michael Togneri
author Xander Ramage
Michael Togneri
author2 Xander Ramage
Christopher Davies
Christian Thomas
Michael Togneri
format Journal article
container_title Physical Review Fluids
container_volume 5
container_issue 10
publishDate 2020
institution Swansea University
issn 2469-990X
doi_str_mv 10.1103/physrevfluids.5.103901
publisher American Physical Society (APS)
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Mechanical Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Mechanical Engineering
url http://orca.cf.ac.uk/135864/
document_store_str 0
active_str 0
description For a family of oscillatory Stokes layers, the spatiotemporal evolution of impulsively excited disturbances is investigated, using direct numerical simulations of the linearized Navier-Stokes equations. The semi-infinite planar Stokes layer is modified to incorporate a low-amplitude, high-frequency harmonic, which provides a simplified model of the external noise found in physical experiments. For the unmodified Stokes layer, impulsively excited disturbances are known to form family-tree-like structures, composed of multiple wave packets. The long-term behavior that is encompassed within these structures is studied, together with the effects upon them of the alterations to the base flow. In the absence of any base-flow modification, the disturbances are discovered to exhibit a subharmonic pattern of temporal growth, with a periodicity that is twice that of the basic state. It is also shown that when linear instability first arises, it takes an absolute rather than a convective form. Inclusion of a high-frequency harmonic into the basic state is found to have a strong and destabilizing impact upon the impulse response. The development of the family-tree-like disturbance structure can be disrupted, changing the character of the absolute instability and promoting its appearance at much reduced Reynolds numbers.
published_date 2020-10-02T04:09:49Z
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score 11.03559

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