Vis enkel innførsel

dc.contributor.authorEllingsen, Simen Andreas Ådnøy
dc.contributor.authorAkselsen, Andreas Holm
dc.contributor.authorChan, Leon
dc.date.accessioned2021-09-17T08:38:16Z
dc.date.available2021-09-17T08:38:16Z
dc.date.created2021-09-10T12:44:21Z
dc.date.issued2021
dc.identifier.citationJournal of Fluid Mechanics. 2021, 926 .en_US
dc.identifier.issn0022-1120
dc.identifier.urihttps://hdl.handle.net/11250/2778838
dc.description.abstractWe present direct numerical simulation of a mechanism for creating longitudinal vortices in pipe flow, compared with a model theory. By furnishing the pipe wall with a pattern of crossing waves, secondary flow in the form of streamwise vortex pairs is created. The mechanism, ‘CL1’, is kinematic and known from oceanography as a driver of Langmuir circulation. CL1 is strongest when the ‘wall wave’ vectors make an acute angle with the axis, φ=10∘–20∘, changes sign near 45∘ and is weak and of opposite sign beyond this angle. A competing, dynamic mechanism driving secondary flow in the opposite sense is also observed, created by the azimuthally varying friction. Whereas at smaller angles ‘CL1’ prevails, the dynamic effect dominates when φ≳45∘, reversing the flow. Curiously, the circulation strength is a faster-than-linearly increasing function of Reynolds number for small φ. We explore an analogy with Prandtl's secondary motion of the second kind in turbulence. A transport equation for average streamwise vorticity is derived, and we analyse it for three different crossing angles, φ=18.6∘,45∘ and 60∘. Mean-vorticity production is organised in a ring-like structure with the two rings contributing to rotating flow in opposite senses. For the larger φ, the inner ring decides the main swirling motion, whereas for φ=18.6∘, outer-ring production dominates. For the larger angles, the outer ring is mainly driven by advection of vorticity and the inner by deformation (stretching) whereas, for φ=18.6∘, both contribute approximately equally to production in the outer ring.en_US
dc.language.isoengen_US
dc.publisherOxford University Pressen_US
dc.titleDesigning vortices in pipe flow with topography-driven Langmuir circulationen_US
dc.typePeer revieweden_US
dc.typeJournal articleen_US
dc.description.versionacceptedVersionen_US
dc.source.pagenumber24en_US
dc.source.volume926en_US
dc.source.journalJournal of Fluid Mechanicsen_US
dc.identifier.doihttps://doi.org/10.1017/jfm.2021.696
dc.identifier.cristin1933247
dc.description.localcodeLocked until 6.3.2022 due to copyright restrictions. This is a pre-copyedited, author-produced version of an article accepted for publication following peer review.en_US
cristin.ispublishedtrue
cristin.fulltextoriginal
cristin.fulltextpostprint
cristin.qualitycode2


Tilhørende fil(er)

Thumbnail

Denne innførselen finnes i følgende samling(er)

Vis enkel innførsel