Volume 127, Number 6, September 2019
|Number of page(s)||5|
|Section||Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics|
|Published online||14 October 2019|
The non-equilibrium part of the inertial range in decaying homogeneous turbulence
1 Université Grenoble Alpes, CNRS, Grenoble- INP, LEGI - F-38000, Grenoble, France
2 Department of Aeronautics, Imperial College London - London, UK
(a) Univ. Lille, CNRS, ONERA, Arts et Métiers ParisTech, Centrale Lille, FRE 2017 - LMFL - Laboratoire de Mécanique des fluides de Lille - Kampé de Feriet, F-59000 Lille, France; email@example.com
Received: 18 July 2019
Accepted: 29 September 2019
We use two related non-stationarity functions as measures of the degree of scale-by-scale non-equilibrium in homogeneous isotropic turbulence. The values of these functions indicate significant non-equilibrium at the upper end of the inertial range. Wind tunnel data confirm Lundgren's prediction that the two-point separation r where the second- and third-order structure functions are closest to their Kolmogorov scalings is proportional to the Taylor length-scale λ, and that both structure functions increasingly distance themselves from their Kolmogorov equilibrium form as r increases away from λ throughout the inertial range. With the upper end of the inertial range in non-equilibrium irrespective of Reynolds number, it is not possible to justify the Taylor-Kolmogorov turbulence dissipation scaling on the basis of Kolmogorov equilibrium.
PACS: 47.27.Ak – Fundamentals / 47.27.Gs – Isotropic turbulence; homogeneous turbulence / 47.27.Jv – High-Reynolds-number turbulence
© EPLA, 2019
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