Energetics of instability modes in the cylinder wake

Z. Y. Ng, T. Vo, G. J. Sheard

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This study investigates the perturbation kinetic energy budget of the instability modes in the circular cylinder wake using the out-of-plane averaged perturbation kinetic energy (PKE) equation. This equation relates to the instability growth rates predicted through linear stability analysis techniques and provides a means to understand the sources through which the linear modes grow on the two-dimensional base flow. In this study, the linear modes A and B are studied at their corresponding transition Reynolds number. The most dominant rate of production terms contributing to the mode A and B instability growth are those derived from cross-flow gradients of the base flow velocity, although the terms for mode B occur at higher rates than those for mode A. The locus of the regions with high production rates within the flow field (concerning the sum of the two dominant production terms) shows that the perturbations for mode A develop most rapidly in the elliptical core of the forming vortex, while those for mode B are amplified most in the interface between the two forming vortices, reaching a maximum when the vortex sheds from the cylinder. The mode A unstable flow then describes weak secondary regions of production within the elliptical vortex cores further downstream, and is a feature absent in mode B.

Original languageEnglish
Title of host publicationProceedings of the 21st Australasian Fluid Mechanics Conference
EditorsTimothy C.W. Lau, Richard M. Kelso
Place of PublicationPerth WA Australia
PublisherAustralasian Fluid Mechanics Society
Number of pages4
ISBN (Print)9780646597843
Publication statusPublished - 2018
EventAustralasian Fluid Mechanics Conference 2018 - Adelaide Convention Centre, Adelaide, Australia
Duration: 10 Dec 201813 Dec 2018
Conference number: 21st
http://www.afms.org.au/proceedings/21.html (Proceedings)


ConferenceAustralasian Fluid Mechanics Conference 2018
Abbreviated titleAFMC 2018
Internet address

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