Journal of Fluid Mechanics



The structure of intense vorticity in isotropic turbulence


Javier  Jiménez a1p1, Alan A.  Wray a2, Philip G.  Saffman a3 and Robert S.  Rogallo a2
a1 Centre for Turbulence Research, Stanford University, Stanford, CA 94305, USA
a2 NASA Ames Research Centre, Moffett Field, CA 94035, USA
a3 Applied Mathematics, California Institute of Technology, Pasadena, CA 91125, USA

Article author query
jiménez j   [Google Scholar] 
wray aa   [Google Scholar] 
saffman pg   [Google Scholar] 
rogallo rs   [Google Scholar] 
 

Abstract

The structure of the intense-vorticity regions is studied in numerically simulated homogeneous, isotropic, equilibrium turbulent flow fields at four different Reynolds numbers, in the range Reλ = 35–170. In accordance with previous investigators this vorticity is found to be organized in coherent, cylindrical or ribbon-like, vortices (‘worms’). A statistical study suggests that they are simply especially intense features of the background, O(ω′), vorticity. Their radii scale with the Kolmogorov microscale and their lengths with the integral scale of the flow. An interesting observation is that the Reynolds number γ/ν, based on the circulation of the intense vortices, increases monotonically with Reλ, raising the question of the stability of the structures in the limit of Reλ [rightward arrow] [infty infinity]. Conversely, the average rate of stretching of these vortices increases only slowly with their peak vorticity, suggesting that self-stretching is not important in their evolution. One- and two-dimensional statistics of vorticity and strain are presented; they are non-Gaussian and the behaviour of their tails depends strongly on the Reynolds number. There is no evidence of convergence to a limiting distribution in this range of Reλ, even though the energy spectra and the energy dissipation rate show good asymptotic properties in the higher-Reynolds-number cases. Evidence is presented to show that worms are natural features of the flow and that they do not depend on the particular forcing scheme.

(Published Online April 26 2006)
(Received November 17 1992)


Correspondence:
p1 Permanent address: School of Aeronautics, Pl. Cardenal Cisneros 3, 28040 Madrid, Spain.


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