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Media type:
E-Article
Title:
The role of coherent vortices near the turbulent/non-turbulent interface in a planar jet
Contributor:
da Silva, Carlos Bettencourt;
dos Reis, Ricardo José Nunes
Published:
The Royal Society, 2011
Published in:
Philosophical Transactions: Mathematical, Physical and Engineering Sciences, 369 (2011) 1937, Seite 738-753
Language:
English
ISSN:
1364-503X
Origination:
Footnote:
Description:
The role of coherent vortices near the turbulent /non-turbulent (T/NT) interface in a turbulent plane jet is analysed by a direct numerical simulation (DNS). The coherent vortices near the jet edge consist of large-scale vortical structures (LSVSs) maintained by the mean shear and intense vorticity structures (IVSs) created by the background fluctuating turbulence field. The radius of the LSVS is equal to the Taylor micro-scale R lsvs ≈λ, while the radius of the IVS is of the order of the Kolmogorov micro-scale R ivs ~η. The LSVSs are responsible for the observed vorticity jump at the T/NT interface, being of the order of the Taylor micro-scale. The coherent vortices in the proximity of the T/NT interface are preferentially aligned with the tangent to the T/NT interface and are responsible for the viscous dissipation of kinetic energy near the T/NT interface and to the characteristic shape of the enstrophy viscous diffusion observed at that location.