Volume 87, Number 4, August 2009
Article Number 44007
Number of page(s) 6
Section Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics
Published online 15 September 2009
EPL, 87 (2009) 44007
DOI: 10.1209/0295-5075/87/44007

Drag fluctuations of a disk in a turbulent jet: Effect of turbulent scales averaging

B. Thiria1, O. Cadot1 and J.-F. Beaudoin2

1   Unité de Mécanique, École supérieure de Techniques avancées - Chemin de la Hunière, 91761 Palaiseau Cedex, France, EU
2   Department of Research and Innovation, PSA Peugeot-Citroen - 2 route de Gisy, 78943 Vélizy-Villacoublay, France, EU

received 13 March 2009; accepted in final form 13 August 2009; published August 2009
published online 15 September 2009

The drag fluctuations of a disk placed on the axis of a turbulent incompressible jet are studied at Re=70000. Statistics and spectra have been obtained for different disk sizes. A significant spatial averaging effect is observed in the symmetrization of probability distribution function and in the low-pass filtering of spectra. These effects are associated with a redistribution of the high-frequencies energy to the low frequencies. It is shown that this redistribution is done in such a way that the rms value of the drag fluctuations increases linearly with the disk surface. These results concerning the drag fluctuations are compared and found to be consistent with fluctuations of a global kinetic energy extracted from the turbulent field in front of the disk.

47.27.wg - Turbulent jets.
47.27.Gs - Isotropic turbulence; homogeneous turbulence.

© EPLA 2009