Sub-Kolmogorov-scale fluctuations in fluid turbulence

Department of Mechanical Engineering, Technische Universität Ilmenau - D-98684 Ilmenau, Germany

Received: 4 July 2007
Accepted: 1 October 2007

Abstract

We relate the intermittent fluctuations of velocity gradients in turbulence to a whole range of local dissipation scales generalizing the picture of a single mean dissipation length. The statistical distribution of these local dissipation scales as a function of Reynolds number is determined in numerical simulations of forced homogeneous isotropic turbulence with a spectral resolution never applied before which exceeds the standard one by at least a factor of eight. The core of the scale distribution agrees well with a theoretical prediction. Increasing Reynolds number causes the generation of ever finer local dissipation scales. This is in line with a less steep decay of the large wave number energy spectra in the dissipation range. The energy spectrum for the highest accessible Taylor microscale Reynolds number = 107 does not show a bottleneck.