DNS of the very large anisotropic scales in a turbulent channel

TL;DR

This paper presents direct numerical simulations of turbulent channel flow at high Reynolds numbers to analyze the size and scaling of large anisotropic structures in the outer layer of wall turbulence.

Contribution

It provides new insights into the organization and scaling of large outer-layer structures in turbulent wall flows through detailed DNS data.

Findings

Large structures contain significant kinetic energy and Reynolds stresses.

Outer layer structures scale with Reynolds number.

Simulation results enhance understanding of turbulence organization.

Abstract

The large structures in the outer layer of turbulent wall flows are of great physical importance, because they contain a substantial fraction of the streamwise kinetic energy and of the Reynolds stresses. Nevertheless, the organization of the outer region of wall turbulence has historically received less attention than that of the inner region, and as a consequence, it is still the subject of many open experimental and theoretical questions. In order to address some of those questions, we have performed direct numerical simulations of the turbulent incompressible flow in plane channels at Reynolds numbers 185 - 550. This paper presents some of the results of this simulation, focusing on the statistical description of the size of the large structures of the streamwise velocity and on its scaling with Reynolds number.