The turbulent Kármán vortex

J. G. Chen, Y. Zhou, R. A. Antonia, T. M. Zhou

Research output: Contribution to journalArticle

Abstract

This work focuses on the temperature (passive scalar) and velocity characteristics within a turbulent Kármán vortex using a phase-averaging technique. The vortices are generated by a circular cylinder, and the three components of the fluctuating velocity and vorticity vectors, ui and ωi (i=1; 2; 3), are simultaneously measured, along with the fluctuating temperature θ and the temperature gradient vector, at nominally the same spatial point in the plane of mean shear at x=d =10, where x is the streamwise distance from the cylinder axis and d is the cylinder diameter. We believe this is the first time the properties of fluctuating velocity, temperature, vorticity and temperature gradient vectors have been explored simultaneously within the Kármán vortex in detail. The Reynolds number based on d and the free-stream velocity is 2:5 × 10 3 . The phase-averaged distributions of θ and ui follow closely the Gaussian distribution for r/d ≥ 0:2 (r is the distance from the vortex centre), but not for r/d > 0:2. The collapse of the distributions of the mean-square streamwise derivative of the velocity fluctuations within the Kármán vortex implies that the velocity field within the vortex tends to be more locally isotropic than the flow field outside the vortex. A possible physical explanation is that the large and small scales of velocity and temperature fields are statistically independent of each other near the Kármán vortex centre, but interact vigorously outside the vortex, especially in the saddle region, due to the action of coherent strain rate.

Original languageEnglish
Pages (from-to)92-112
Number of pages21
JournalJournal of Fluid Mechanics
Volume871
DOIs
Publication statusPublished - 25 Jul 2019

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