Eur. Phys. J. B 45, 289-292 (2005)
https://doi.org/10.1140/epjb/e2005-00196-1

Global injected power statistics in a turbulent system: degrees of freedom and aspect ratio effect

¹ Laboratoire de Mécanique, Physique et Géosciences, Université du Havre, 25 Rue Philippe Lebon, 76058 Le Havre Cedex, France
² École Nationale Supérieure de Techniques Avancées, Unité de Mécanique, Chemin de la hunière, 91760 Palaiseau Cedex, France

Corresponding author: ^a cadot@ensta.fr

Received: 21 December 2004
Revised: 31 March 2005
Published online: 6 July 2005

Abstract

The properties of the global energy injection rate of a closed turbulent flow produced between two counter-rotating disks are studied. The statistics of this global quantity are measured when the aspect ratio (defined as the ratio of the disk diameter to the separating distance between both disks) is modified. It is shown that the non-Gaussian statistics obtained at a low aspect ratio becomes Gaussian for a large aspect ratio. This effect is accompanied with a large decrease of the fluctuation rate. These results indicate the total energy injection rate to obey the central limit theorem. It is also shown that the number of degrees of freedom of total injection rate may be related to the number of independent large scale structures present in the flow.