Invariant solutions of minimal large-scale structures in turbulent channel flow for Reτ up to 1000 - Archive ouverte HAL
Article Dans Une Revue Journal of Fluid Mechanics Année : 2016

Invariant solutions of minimal large-scale structures in turbulent channel flow for Reτ up to 1000

Résumé

Understanding the origin of large-scale structures in high-Reynolds-number wall turbulence has been a central issue over a number of years. Recently, Rawat et al. (J. Fluid Mech., vol. 782, 2015, pp. 515–540) have computed invariant solutions for the large-scale structures in turbulent Couette flow at Reτ 128 using an overdamped large-eddy simulation with the Smagorinsky model to account for the effect of the surrounding small-scale motions. Here, we extend this approach to Reynolds numbers an order of magnitude higher in turbulent channel flow, towards the regime where the large-scale structures in the form of very-large-scale motions (long streaky motions) and large-scale motions (short vortical structures) emerge energetically. We demonstrate that a set of invariant solutions can be computed from simulations of the self-sustaining large-scale structures in the minimal unit (domain of size Lx = 3.0h streamwise and Lz = 1.5h spanwise) with midplane reflection symmetry at least up to Reτ = 1000. By approximating the surrounding small scales with an artificially elevated Smagorinsky constant, a set of equilibrium states are found, labelled upper- and lower-branch according to their associated drag. It is shown that the upper-branch equilibrium state is a reasonable proxy for the spatial structure and the turbulent statistics of the self-sustaining large-scale structures.
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Dates et versions

hal-01392442 , version 1 (04-11-2016)

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Yongyun Hwang, Ashley P. Willis, Carlo Cossu. Invariant solutions of minimal large-scale structures in turbulent channel flow for Reτ up to 1000. Journal of Fluid Mechanics, 2016, vol. 802, pp. R1-1-R1-13. ⟨10.1017/jfm.2016.470⟩. ⟨hal-01392442⟩
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