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

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, Re-theta, 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 voracity, 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 TINT 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. 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license