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Scale interactions in turbulent rotating planar Couette flow: insight through the Reynolds stress transport
Tokyo Univ Sci, Dept Mech Engn, Yamazaki 2641, Noda, Chiba 2788510, Japan..
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics.ORCID iD: 0000-0002-1146-3241
2019 (English)In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 879, p. 255-295, article id PII S0022112019006682Article in journal (Refereed) Published
Abstract [en]

In turbulent planar Couette flow under anticyclonic spanwise system rotation, large-scale roll-cell structures arise due to a Coriolis-force-induced instability. The structures are superimposed on smaller-scale turbulence, and with increasing angular velocity (Omega(z)) such roll cells dominate the flow field and small-scale turbulence is instead suppressed in a certain rotation number range 0 < Ro less than or similar to 0.1 (Ro = 2 Omega(z)h/U-w, where h is the channel half-width, U-w the wall velocity). At low rotation numbers around Ro approximate to 0.02 both large-scale roll cells and smaller-scale turbulence coexist. In the present study, we investigate interaction between these structures through a scale-by-scale analysis of the Reynolds stress transport. We show that at low rotation numbers Ro approximate to 0.01 the turbulence productions by the mean flow gradient and the Coriolis force occur at different scales and thereby the turbulent energy distribution over a wide range of scales is maintained. On the other hand at higher rotation numbers Ro greater than or similar to 0.05, a zero-absolute-vorticity state is established and production of small scales from the mean shear disappears although large-scale turbulence production is maintained through the Coriolis force. At high enough Reynolds numbers, where scale separation between the near-wall structures and the roll cells is relatively distinct, transition between these different Ro regimes is found to occur rather abruptly around Ro approximate to 0.02, resulting in a non-monotonic behaviour of the wall shear stress as a function of Ro. It is also shown that at such an intermediate rotation number the roll cells interact with smaller scales by moving near-wall structures towards the core region of the channel, by which the Reynolds stress is transported from relatively small scales near the wall towards larger scales in the channel centre. Such Reynolds stress transport by scale interaction becomes increasingly significant as the Reynolds number increases, and results in a reversed mean velocity gradient at the channel centre at high enough Reynolds numbers.

Place, publisher, year, edition, pages
CAMBRIDGE UNIV PRESS , 2019. Vol. 879, p. 255-295, article id PII S0022112019006682
Keywords [en]
rotating turbulence, turbulent boundary layers
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-261930DOI: 10.1017/jfm.2019.668ISI: 000487791200001OAI: oai:DiVA.org:kth-261930DiVA, id: diva2:1361308
Note

QC 20191015

Available from: 2019-10-15 Created: 2019-10-15 Last updated: 2019-10-15Bibliographically approved

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Alfredsson, P. Henrik

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