Analysis of conditional statistics obtained near the turbulent/non-turbulent interface of turbulent boundary layers

• Published in: Journal of fluids and structures 2015-02, Vol.53, p.50-57
• Main Authors: Ishihara, Takashi, Ogasawara, Hiroki, Hunt, Julian C.R.
• Format: Article
• Language: English
• Subjects: Blocking mechanism; Computational fluid dynamics; Conditional statistics; Fluctuation; Fluid flow; New technology; Statistics; Turbulence; Turbulent boundary layer; Turbulent flow; Turbulent/non-turbulent interface
• ISSN: 0889-9746; 1095-8622
• DOI: 10.1016/j.jfluidstructs.2014.10.008

Direct numerical simulations of turbulent boundary layers (TBL) along a flat plate are used to study the properties of turbulent/non-turbulent (T/NT) interface of the TBL. The values of the momentum-thickness-based Reynolds numbers, Reθ, used for this study, are 500–2200. Analysis of the conditional statistics near the interface of the TBL shows that there are a small peak in the spanwise vorticity, and an associated small jump in streamwise velocity. It is shown that the interfacial layer has an inertia-viscous double structure which consists of a turbulent sublayer with a thickness of the order of the Taylor micro-scale and its outer boundary with a thickness of the order of the Kolmogorov length scale. The velocity jump near the T/NT interface of the TBL is of the order of the rms value of velocity fluctuations near the interface. Conditional cross correlations of the streamwise or the wall-normal velocity fluctuations change sharply across the interface, which are consistent with the blocking mechanism of the interface.