Statistics of the Energy Dissipation Rate and Local Enstrophy in Turbulent Channel Flow

TL;DR

This study uses high-resolution simulations to analyze the statistical behavior of energy dissipation and enstrophy in turbulent channel flows, revealing wall distance and Reynolds number effects on small-scale turbulence.

Contribution

It provides detailed higher-order statistics of dissipation and enstrophy across different wall regions and Reynolds numbers, including conditional analysis based on vortical structures.

Findings

Dissipation and enstrophy moments depend on wall distance.

Reynolds number effects are observed at the logarithmic layer edge.

Small-scale fluctuations become constant at higher Reynolds numbers beyond a certain wall distance.

Abstract

Using high-resolution direct numerical simulations, the height and Reynolds number dependence of higher-order statistics of the energy dissipation rate and local enstrophy are examined in incompressible, fully-developed turbulent channel flow. The statistics are studied over a range of wall distances, spanning the viscous sublayer to the channel flow centerline, for friction Reynolds numbers $Re_\tau = 180$ and $Re_\tau = 381$. The high resolution of the simulations allows dissipation and enstrophy moments up to fourth order to be calculated. These moments show a dependence on wall distance, and Reynolds number effects are observed at the edge of the logarithmic layer. Conditional analyses based on locations of intense rotation are also carried out in order to determine the contribution of vortical structures to the dissipation and enstrophy moments. Our analysis shows that, for the simulation at the larger Reynolds number, small-scale fluctuations of both dissipation and enstrophy become relatively constant for $z^+ \gtrsim 100$.