Nonlinear dynamics of forced baroclinic critical layers II
dc.contributor.author | Wang, C | |
dc.contributor.author | Balmforth, NJ | |
dc.date.accessioned | 2021-04-23T14:22:59Z | |
dc.date.issued | 2021-04-30 | |
dc.description.abstract | Baroclinic critical levels arise as singularities in the inviscid linear theory of waves propagating through a stratified, horizontally directed and sheared flow. For a steady wave forcing, disturbances grow secularly over the criticial layers surrounding these levels, generating a jet-like defect in the mean flow. We use a matched asymptotic expansion to furnish a reduced model of the nonlinear dynamics of such defects. By solving the linear initial-value problem for small perturbations to the defect, we establish that secondary instabilities appear at later times. Because the defect is time-dependent, conventional normal-mode analysis is quantitatively inaccurate, but does successfully predict the occurrence of the secondary instability. The instability has a singular character in that disturbances with the shortest horizontal wavelength grow most vigorously at late times, unless dissipation is included. The instability can be suppressed by weak viscosity; by itself, thermal dissipation delays, but does not arrest instability. Numerical computations with the dissipative reduced model demonstrate that the secondary instability saturates as the defect rolls up into a coherent vortical structure. This structure excites a new wave propagating at a different phase speed, thereby forcing a new set of baroclinic critical levels. The implications for self-replication are discussed. | en_GB |
dc.identifier.citation | Vol. 917, article A48 | en_GB |
dc.identifier.doi | 10.1017/jfm.2021.297 | |
dc.identifier.uri | http://hdl.handle.net/10871/125457 | |
dc.language.iso | en | en_GB |
dc.publisher | Cambridge University Press | en_GB |
dc.rights | © The Author(s), 2021. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. | |
dc.title | Nonlinear dynamics of forced baroclinic critical layers II | en_GB |
dc.type | Article | en_GB |
dc.date.available | 2021-04-23T14:22:59Z | |
dc.identifier.issn | 0022-1120 | |
dc.description | This is the final version. Available on open access from Cambridge University Press via the DOI in this record | en_GB |
dc.identifier.eissn | 1469-7645 | |
dc.identifier.journal | Journal of Fluid Mechanics | en_GB |
dc.rights.uri | https://creativecommons.org/licenses/by/4.0/ | en_GB |
dcterms.dateAccepted | 2021-03-27 | |
rioxxterms.version | VoR | en_GB |
rioxxterms.licenseref.startdate | 2021-03-27 | |
rioxxterms.type | Journal Article/Review | en_GB |
refterms.dateFCD | 2021-04-23T14:11:33Z | |
refterms.versionFCD | AM | |
refterms.dateFOA | 2021-06-10T13:02:29Z | |
refterms.panel | B | en_GB |
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Except where otherwise noted, this item's licence is described as © The Author(s), 2021. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.