V Grenard et al J. Stat. Mech. (2008) L09003 doi:10.1088/1742-5468/2008/09/L09003
V Grenard, N B Garnier and A Naert
Show affiliationsWe report on measurements of the transverse fluctuations of a string in a turbulent air jet flow. Harmonic modes are excited by the fluctuating drag force, at different wavenumbers. This simple mechanical probe makes it possible to measure excitations of the flow at specific scales, averaged over space and time: it is a scale-resolved, global measurement. We also measure the dissipation associated with the string motion, and we consider the ratio of the fluctuations to the dissipation (FDR). In an exploratory approach, we investigate the concept of effective temperature defined through the FDR. We compare our observations with other definitions of temperature in turbulence. From the theory of Kolmogorov (1941), we derive the exponent −11/3 expected for the spectrum of the fluctuations. This simple model and our experimental results are in good agreement, over the range of wavenumbers and Reynolds number accessible (74 000≤Re≤170 000).
E-print Number: 0704.0325
Cited: by |
Refers: to
47.80.Fg Pressure and temperature measurements
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
76Fxx Turbulence (See also 58F13, 58F27, 60Gxx, 60Jxx)
82Cxx Time-dependent statistical mechanics (dynamic and nonequilibrium)
Issue 09 (September 2008)
Received 19 June 2008, accepted for publication 29 August 2008
Published 29 September 2008
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