Fluctuation-dissipation relation on a Melde string in a turbulent flow, considerations on a "dynamical temperature"

Abstract

We 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 wave-numbers. 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 to the string motion, and we consider the ratio of the fluctuations over dissipation (FDR). In an exploratory approach, we investigate the concept of {\it 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 wave-numbers, and Reynolds number accessible ($74000\le Re\le 170000$).

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References in corpus (2)

• Analytical Solution of the Off-Equilibrium Dynamics of a Long Range Spin-Glass Model
• Energy flow, partial equilibration and effective temperatures in systems with slow dynamics

Cited by in corpus (8)

• The effective temperature
• Dependence of the fluctuation-dissipation temperature on the choice of observable
• Low thermal fluctuations in a system heated out of equilibrium
• Susceptibility divergence, phase transition and multistability of a highly turbulent closed flow
• Influence of flux balance on the generalized chemical potential in mass transport models
• Extended Nyquist formula for a resistance subject to a heat flow
• Entropy-based characterizations of the observable-dependence of the fluctuation-dissipation temperature
• Effective temperatures for single particle system under dichotomous noise