Abstract
The results from DNS of turbulent channels, together with the solutions of a linear model, are used to investigate the effects of the wall in the dynamics of the logarithmic and outer regions. The effect of wall-roughness, modeled here by wall-disturbances, is shown to be small in the active scales of the flow. In particular, the statistical properties of the wall-attached ejections contributing to the Reynolds stresses are independent of the nature of the wall. The linear model shows that these ejections are short-lived events, consistently with the (x, t) spectrum of the DNS. Therefore, they cannot be responsible for the formation of the long streaks of the outer region. Tentatively, we propose a new model where the structures of the logarithmic region are essentially passive, subordinated to the structures of the outer region, reversing the flow of causality usually assumed in wall-bounded turbulence.
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Acknowledgments
This work was supported in part by the Spanish CICYT, under grant TRA2006-08226. OF was supported by a FPI scholarship of the Spanish MEC. The computational resources provided by CIEMAT, CEPBA and BSC are gratefully acknowledged.
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Flores, O., Jiménez, J. (2010). Log-Layer Dynamics in Smooth and Artificially-Rough Turbulent Channels. In: Nickels, T. (eds) IUTAM Symposium on The Physics of Wall-Bounded Turbulent Flows on Rough Walls. IUTAM Bookseries, vol 22. Springer, Dordrecht. https://doi.org/10.1007/978-90-481-9631-9_13
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DOI: https://doi.org/10.1007/978-90-481-9631-9_13
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