Representation of the Reynolds stress tensor through quadrant analysis for a near-neutral atmospheric surface layer flow.

Autor: Chowdhuri, Subharthi, Deb Burman, Pramit Kumar
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Zdroj: Environmental Fluid Mechanics; Feb2020, Vol. 20 Issue 1, p51-75, 25p
Abstrakt: To disseminate the role of the eddy motions on the anisotropic states of the Reynolds stress tensor ( B ), we devise a novel methodology based on the quadrant analysis, where the distributions of the invariants of B are studied on a u ′ – w ′ quadrant plane, with u ′ and w ′ being the turbulent fluctuations in the streamwise and vertical velocities. We apply this methodology to a near-neutral atmospheric surface layer (ASL) flow, derived from a field experiment dataset having multi-level turbulence measurements. The results show that in a near-neutral ASL flow, the anisotropic states of B are determined by the distribution of the streamwise and cross-stream velocity variances ( σ u 2 and σ v 2 ) on the u ′ – w ′ quadrant plane. By studying the contour maps of the invariants of B on the u ′ – w ′ quadrant plane, we discover three distinct zones with elliptical boundaries in the u ′ – w ′ plane, across which the anisotropic states of the eddy motions evolve. We find that the eddy motions which occur Inside the inner elliptical zone display rod-like anisotropy being determined by σ v 2 , Within the annular zone between the inner and outer ellipses display pancake-like anisotropy being determined by both σ u 2 and σ v 2 , Outside the outer elliptical zone display rod-like anisotropy being determined by σ u 2 . We also notice that the distinction between these three zones in the u ′ – w ′ plane is prominent at the lowest measurement level, but becomes progressively indistinguishable as the measurement height increases. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index