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Entropic-skins geometry to describe wall turbulence intermittency

Abstract : In order to describe the phenomenon of intermittency in wall turbulence and, more particularly, the behaviour of moments p r δV and pr ε and intermittency exponents ζP with the order p and distance to the wall, we developed a new geometrical framework called “entropic-skins geometry” based on the notion of scale-entropy which is here applied to an experimental database of boundary layer flows. Each moment has its own spatial multi-scale support Ωp (“skin”). The model assumes the existence of a hierarchy of multi-scale sets Ωp ranged from the “bulk” to the “crest”. The crest noted characterizes the geometrical support where the most intermittent (the highest) fluctuations in energy dissipation occur; the bulk is the geometrical support for the whole range of fluctuations. The model assumes then the existence of a dynamical flux through the hierarchy of skins. The specific case where skins display a fractal structure is Investigated. Bulk fractal dimension Δ f and crest dimension Δ∞ are linked by a scale-entropy flux defining a reversibility efficiency ( )/( ) f γ d = Δ −Δ −Δ ∞ ∞ (d is the embedding dimension). The model, initially developed for homogeneous and isotropic turbulent flows, is applied here to wall bounded turbulence where intermittency exponents are measured by extended self-similarity. We obtained for intermittency exponents the analytical expression [ ] /3 ( (1 ) 3 2) / 3 (3 )(1 ) pp ζ γγ γ p = Δ − + − + −Δ − ∞ ∞ with γ ≈ 0.36 in agreement withexperimental results.
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Submitted on : Saturday, May 16, 2020 - 11:35:45 AM
Last modification on : Thursday, October 21, 2021 - 3:16:35 PM

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  • HAL Id : hal-02605901, version 1
  • IRSTEA : PUB00053585

Citation

D. Queiros Conde, Julien Carlier, L. Grosu, M. Stanislas. Entropic-skins geometry to describe wall turbulence intermittency. Entropy, MDPI, 2015, 17 (4), pp.2198-2217. ⟨hal-02605901⟩

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