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  Statistics, plumes and azimuthally travelling waves in ultimate Taylor-Couette turbulent vortices

Froitzheim, A., Ezeta, R., Huisman, S. G., Merbold, S., Sun, C., Lohse, D., et al. (2019). Statistics, plumes and azimuthally travelling waves in ultimate Taylor-Couette turbulent vortices. Journal of Fluid Mechanics, 876, 733-765. doi:10.1017/jfm.2019.552.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0004-94C3-8 Version Permalink: http://hdl.handle.net/21.11116/0000-0004-94C4-7
Genre: Journal Article

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Froitzheim, A., Author
Ezeta, R., Author
Huisman, S. G., Author
Merbold, S., Author
Sun, C., Author
Lohse, Detlef1, Author              
Egbers, C., Author
Affiliations:
1Max Planck Institute for Dynamics and Self-Organization, Max Planck Society, ou_2063285              

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Free keywords: Taylor-Couette flow; rotating turbulence; turbulent convection
 Abstract: In this paper, we experimentally study the influence of large-scale Taylor rolls on the small-scale statistics and the flow organization in fully turbulent Taylor-Couette flow for Reynolds numbers up to Re-S = 3 x 10(5) . The velocity field in the gap confined by coaxial and independently rotating cylinders at a radius ratio of eta=0.714 is measured using planar particle image velocimetry in horizontal planes at different cylinder heights. Flow regions with and without prominent Taylor vortices are compared. We show that the local angular momentum transport (expressed in terms of a Nusselt number) mainly takes place in the regions of the vortex in- and outflow, where the radial and azimuthal velocity components are highly correlated. The efficient momentum transfer is reflected in intermittent bursts, which becomes visible in the exponential tails of the probability density functions of the local Nusselt number. In addition, by calculating azimuthal energy co-spectra, small-scale plumes are revealed to be the underlying structure of these bursts. These flow features are very similar to the one observed in Rayleigh-Benard convection, which emphasizes the analogies of these systems. By performing a complex proper orthogonal decomposition, we remarkably detect azimuthally travelling waves superimposed on the turbulent Taylor vortices, not only in the classical but also in the ultimate regime. This very large-scale flow pattern, which is most pronounced at the axial location of the vortex centre, is similar to the well-known wavy Taylor vortex flow, which has comparable wave speeds, but much larger azimuthal wavenumbers.

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Language(s): eng - English
 Dates: 2019-08-062019-10-10
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Method: Peer
 Identifiers: DOI: 10.1017/jfm.2019.552
 Degree: -

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Title: Journal of Fluid Mechanics
Source Genre: Journal
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Pages: - Volume / Issue: 876 Sequence Number: - Start / End Page: 733 - 765 Identifier: -