Herbert, E., Daviaud, F., Dubrulle, B., Nazarenko, Sergey and Naso, A. (2012) Dual non-Kolmogorov cascades in a von Kármán flow. EPL (Europhysics Letters), Volume 100 (Number 4). Article number 44003. doi:10.1209/0295-5075/100/44003 ISSN 0295-5075.

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Abstract

The experimental spatial power spectrum of the velocity fluctuations in a von Kármán flow is measured, in a wide range of Reynolds numbers, 102 < Re < 106, for the first time without using the Taylor hypothesis. At high enough Reynolds numbers, the spectra display a clear dual (direct and inverse) cascade. For any Re, the scaling of the direct cascade is steeper than the classical Kolmogorov −5/3 exponent of homogeneous and isotropic 3D turbulence. We then discuss the possibility of dual local and non-local cascades in a 3D turbulent Beltrami (a property satisfied by the von Kármán flow at large scale) flow, with inverse energy cascade and direct helicity cascade, by analogy with 2D turbulence. The corresponding energy spectra are computed in both local and non-local cases, and compared with our experimental results. The inverse cascade scaling is found to be in agreement with the non-local scenario. The direct cascade scaling is close to the non-local scenario for Re 4.104, and switches towards the local scenario at Re > 105.

Item Type:	Journal Article
Divisions:	Faculty of Science, Engineering and Medicine > Science > Mathematics
Journal or Publication Title:	EPL (Europhysics Letters)
Publisher:	Institute of Physics Publishing Ltd.
ISSN:	0295-5075
Official Date:	2012
Dates:	Date Event 2012 Published
Volume:	Volume 100
Number:	Number 4
Page Range:	Article number 44003
DOI:	10.1209/0295-5075/100/44003
Status:	Peer Reviewed
Publication Status:	Published

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