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Turbulence Heat and Mass Transfer 5. Proceedings of the International Symposium on Turbulence Heat and Mass Transfer
September, 25-29, 2006, Dubrovnik, Croatia

DOI: 10.1615/ICHMT.2006.TurbulHeatMassTransf


ISBN Print: 978-1-56700-229-4

ISSN: 2377-2816

Coherent Fine Scale Eddies in Turbulence Transition of Spatially-Developing Mixing Layer

pages 133-136
DOI: 10.1615/ICHMT.2006.TurbulHeatMassTransf.160
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RÉSUMÉ

To investigate the relationship between characteristics of coherent fine scale eddies (CFSEs) and turbulence transition, a direct numerical simulation (DNS) of spatially-developing turbulent mixing layer with Rew,0 = 700 was conducted. The large-scale coherent structures; Kelvin-Helmholtz roller and rib vortex, do not disappear in the transition process and in the fully-developed state, however they are composed of lots of CFSEs. The most expected diameter of the CFSEs is about 8η and does not change in the process of the turbulence transition, while the most expected maximum azimuthal velocity of CFSEs decreases from 2.0uk to 1.2uk. The strain rate acting on the center of CFSEs tends to become weak during the transition, whereas the most expected eigenvalues ratio is maintained to be α : β : γ = −5 : 1 : 4. In addition, the phase averaged energy dissipation rate on the major axis of CFSE becomes low during the turbulence transition.

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