Large-scale length that determines the mean rate of energy dissipation in turbulence

TL;DR

This paper investigates the scaling of energy dissipation in turbulence, proposing that the correlation length of local energy, L(u2), rather than the traditional large-scale length, better determines the mean energy dissipation rate and is independent of flow configuration.

Contribution

The study introduces L(u2) as a key length scale that potentially universalizes the energy dissipation scaling across different turbulent flows.

Findings

L(u2) correlates with energy transfer rates in turbulence.

C(u2) appears independent of flow configuration when scaled by L(u2).

L(u2) may represent the size of energy-containing eddies universally.

Abstract

The mean rate of energy dissipation in turbulence is traditionally assumed to scale with parameters of the energy-containing large scales, i.e., the root-mean-square fluctuation of the longitudinal velocity u and its correlation length L(u). However, the resultant scaling coefficient C(u) is known to depend on the large-scale configuration of the flow. We define the correlation length L(u2) of the local energy u2, study the scaling coefficient C(u2) with experimental data of several flows, and find a possibility that C(u2) does not depend on the flow configuration. Not L(u) but rather L(u2) could scale with the typical size of the energy-containing eddies, so that L(u2) determines the mean rate at which the energy is transferred from those eddies to the smaller eddies and is eventually dissipated into heat. The independence from the flow configuration is also found for the two-point correlations and so on if L(u2) is used to normalize the scale.