Abstract
Abstract
Highlights
Near-wall turbulence is sustained by the so-called self-sustaining process (SSP); that is, streamwise vortices induce low- and high-speed streaks by the advection of the 911 A27-1Y
This gives us a clear view to understand what happens in the real space, when we quantitatively investigate the vortex stretching (§ 3.2) and energy transfer (§ 3.3) among structures in different scales
To reveal the hierarchy of coherent structures of turbulent channel flow and to understand its sustaining mechanism, we have analysed the database of the fully developed turbulence at Reτ = 4179 provided by Lozano-Durán & Jiménez (2014)
Summary
Near-wall turbulence is sustained by the so-called self-sustaining process (SSP); that is, streamwise vortices induce low- and high-speed streaks by the advection of the 911 A27-1Y. Near-wall turbulence is sustained by the so-called self-sustaining process (SSP); that is, streamwise vortices induce low- and high-speed streaks by the advection of the 911 A27-1. The yellow objects in figure 1 are the positive isosurfaces of the second invariant Q of the velocity gradient tensor in turbulent channel flow at the friction Reynolds number Reτ = uτ h/ν = 4179 (see § 2.1 for the details of the database). The quantities related to the velocity are appropriate for extracting the largest-scale structures, whereas those related to its gradients are appropriate for extracting the smallest-scale structures. This is the reason why the velocity has been often used for investigating large-scale motions (LSM). Since one can extract the large-scale structures by visualizing LSM and/or VLSM with the velocity (or the filtered velocity), many authors (e.g. Adrian 2007; Hutchins & Marusic 2007; Monty et al 2007; Dennis & Nickels 2011a,b; Baltzer, Adrian & Wu 2013; Lee et al 2014; Lee, Sung & Zaki 2017; Kevin, Monty & Hutchins 2019b) examined large-scale streaky velocity structures and their relation to large-scale vortices
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