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Vorticity organization in the outer layer of turbulent channels with disturbed walls

  • OSCAR FLORES (a1), JAVIER JIMÉNEZ (a1) (a2) and JUAN C. DEL ÁLAMO (a3)

The vortex clusters in the turbulent outer region of rough- and smooth-walled channels, and their associated velocity structures, are compared using data from numerical experiments at friction Reynolds numbers Reτ ≤ 674. The results indicate that the roughness of the wall does not affect their properties, particularly the existence of wall-detached and wall-attached populations, and the self-similar size distribution of the latter. The average flow field conditioned to the attached clusters reveals similar conical structures of low streamwise velocity for the rough- and smooth-walled cases, which eventually grow into the global modes previously identified from spectral analysis. We conclude that the vortex clusters of the turbulent outer region either originate away from the wall, or quickly forget their origin, in agreement with Townsend's similarity hypothesis.

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O. M. Bakken , P. A. Krogstad , A. Ashfarian & H. I. Andersson 2005 Reynolds number effects in the outer layer of the turbulent flow in a channel with rough walls. Phys. Fluids 17, 065101.

K. A. Flack , M. P. Schultz & T. A. Shapiro 2005 Experimental support for Townsend's Reynolds number similarity hypothesis on rough walls. Phys. Fluids 17, 035102.

J. Jiménez 2004 Turbulent flows over rough walls. Annu. Rev. Fluid Mech. 36, 173196.

M. Metzger , B. J. McKeon & H. Holmes 2007 The near-neutral atmospheric surface layer: turbulence and non-stationarity. Phil. Trans. R. Soc. Lond. A 365, 859876.

S. K. Robinson 1991 aCoherent motions in the turbulent boundary layer. Annu. Rev. Fluid Mech. 23, 601639.

M. Tanahashi , S.-J. Kang , T. Miyamoto , S. Shiokawa & T. Miyauchi 2004 Scaling of fine scale eddies in turbulent channel flows up to Reτ = 800. Intl J. Heat Fluid Flow 25, 331340.

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Journal of Fluid Mechanics
  • ISSN: 0022-1120
  • EISSN: 1469-7645
  • URL: /core/journals/journal-of-fluid-mechanics
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