Turbulence dynamics near a turbulent/non-turbulent interface

• Tipo: Artigo em Revista Científica Internacional
• Data: 2012

Autores

Teixeira, MAC (Autor) Outra; da Silva, CB (Autor) Outra

Revista

Título: Journal of Fluid Mechanics

Vol. 695

Páginas: 257-287

ISSN: 0022-1120

Editora: Cambridge University Press

Indexação

ISI Web of Knowledge - 19 Citações

Scopus - 23 Citações

Outras Informações

ID Authenticus: P-002-C09

DOI: 10.1017/jfm.2012.17

Abstract (EN): The characteristics of the boundary layer separating a turbulence region from an irrotational (or non-turbulent) flow region are investigated using rapid distortion theory (RDT). The turbulence region is approximated as homogeneous and isotropic far away from the bounding turbulent/non-turbulent (T/NT) interface, which is assumed to remain approximately flat. Inviscid effects resulting from the continuity of the normal velocity and pressure at the interface, in addition to viscous effects resulting from the continuity of the tangential velocity and shear stress, are taken into account by considering a sudden insertion of the T/NT interface, in the absence of mean shear. Profiles of the velocity variances, turbulent kinetic energy (TKE), viscous dissipation rate (epsilon), turbulence length scales, and pressure statistics are derived, showing an excellent agreement with results from direct numerical simulations (DNS). Interestingly, the normalized inviscid flow statistics at the T/NT interface do not depend on the form of the assumed TKE spectrum. Outside the turbulent region, where the flow is irrotational (except inside a thin viscous boundary layer), epsilon decays as z(-6), where z is the distance from the T/NT interface. The mean pressure distribution is calculated using RDT, and exhibits a decrease towards the turbulence region due to the associated velocity fluctuations, consistent with the generation of a mean entrainment velocity. The vorticity variance and epsilon display large maxima at the T/NT interface due to the inviscid discontinuities of the tangential velocity variances existing there, and these maxima are quantitatively related to the thickness delta of the viscous boundary layer (VBL). For an equilibrium VBL, the RDT analysis suggests that delta similar to eta (where eta is the Kolmogorov microscale), which is consistent with the scaling law identified in a very recent DNS study for shear-free T/NT interfaces.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 31