Please use this identifier to cite or link to this item: http://bura.brunel.ac.uk/handle/2438/16980
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dc.contributor.authorAppelquist, E-
dc.contributor.authorSchlatter, P-
dc.contributor.authorAlfredsson, PH-
dc.contributor.authorLingwood, RJ-
dc.date.accessioned2018-10-15T10:25:46Z-
dc.date.available2016-09-25-
dc.date.available2018-10-15T10:25:46Z-
dc.date.issued2016-
dc.identifier.citationJournal of Fluid Mechanics, 2016, 803 pp. 332 - 355en_US
dc.identifier.issn0022-1120-
dc.identifier.urihttp://bura.brunel.ac.uk/handle/2438/16980-
dc.description.abstractDirect numerical simulations based on the incompressible nonlinear Navier–Stokes equations of the flow over the surface of a rotating disk have been conducted. An impulsive disturbance was introduced and its development as it travelled radially outwards and ultimately transitioned to turbulence has been analysed. Of particular interest was whether the nonlinear stability is related to the linear stability properties. Specifically three disk-edge conditions were considered; (i) a sponge region forcing the flow back to laminar flow, (ii) a disk edge, where the disk was assumed to be infinitely thin, and (iii) a physically-realistic disk edge of finite thickness. This work expands on the linear simulations presented by Appelquist et al. (J. Fluid. Mech., vol. 765, 2015, pp. 612-631), where, for case (i), this configuration was shown to be globally linearly unstable when the sponge region effectively models the influence of the turbulence on the flow field. In contrast, case (ii) was mentioned there to be linearly globally stable, and here, where nonlinearity is included, it is shown that both case (ii) and (iii) are nonlinearly globally unstable. The simulations show that the flow can be globally linearly stable if the linear wavepacket has a positive front velocity. However, in the same flow field, a nonlinear global instability can emerge, which is shown to depend on the outer turbulent region generating a linear inward-travelling mode that sustains a transition-front within the domain. The results show that the front position does not approach the critical Reynolds number for the local absolute instability, R = 507. Instead, the front approaches R = 583 and both the temporal frequency and spatial growth rate correspond to a global mode originating at this position.en_US
dc.description.sponsorshipSwedish Research Councilen_US
dc.format.extent332 - 355-
dc.language.isoenen_US
dc.publisherCambridge University Pressen_US
dc.subjectBoundary layer stabilityen_US
dc.subjectRotating flowsen_US
dc.subjectAbsolute/convective instabilityen_US
dc.titleOn the global nonlinear instability of the rotating-disk flow over a finite domainen_US
dc.typeArticleen_US
dc.identifier.doihttp://dx.doi.org/10.1017/jfm.2016.506-
dc.relation.isPartOfJournal of Fluid Mechanics-
pubs.publication-statusPublished-
pubs.volume803-
Appears in Collections:Dept of Mechanical and Aerospace Engineering Research Papers

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