Full Program »

Vorticity Statistics and the Time Scales of Turbulent Strain

PDF
0.2MB

Time scales of turbulent strain activity, denoted as the strain persistence times of first and second order, are obtained from time-dependent expectation values and correlation functions of lagrangian rate-of-strain eigenvalues taken in particularly defined statistical ensembles. Our approach is based on a gaussian closure approximation for single-point vorticity statistics, devised to yield a simple and computationally efficient method for the evaluation of the strain persistence times. We find that softly divergent prefactors correct the usual “1/s” time-scale estimate of standard turbulence phenomenology, a fact that turns out to be of fundamental importance in the emergence of turbulent intermittency. The theoretical framework is supported by a straightforward analysis of direct numerical simulation data.

Author(s):

Luca Moriconi    
Instituto de Física - Universidade Federal do Rio de Janeiro
Brazil

Rodrigo Pereira    
Divisão de Metrologia em Dinâmica de Fluidos - Instituto Nacional de Metrologia, Normalização e Qualidade Industrial
Brazil