TY - JOUR AB - An examination is undertaken of the validity and limitations of the quasi-steady hypothesis of near-wall turbulence. This hypothesis is based on the supposition that the statistics of the turbulent fluctuations are universal if scaled by the local, instantaneous, wall shear when its variations are determined from footprints of large-scale, energetic, structures that reside in the outer part of the logarithmic layer. The examination is performed with the aid of direct numerical simulation data for a single Reynolds number, which are processed in a manner that brings out the variability of locally scaled statistics when conditioned on the local value of the wall friction. The key question is to what extent this variability is insignificant, thus reflecting universality. It is shown that the validity of the quasi-steady hypothesis is confined, at best, to a thin layer above the viscous sublayer. Beyond this layer, substantial variations in the conditioned shear-induced production rate of large-scale turbulence cause substantial departures from the hypothesis. Even within the wall-proximate layer, moderate departures are provoked by large-scale distortions in the conditioned strain rate that result in variations in small-scale production of turbulence down to the viscous sublayer. AU - Agostini,L AU - Leschziner,M DO - 10.1017/jfm.2019.395 EP - 12 PY - 2019/// SN - 0022-1120 SP - 1 TI - On the departure of near-wall turbulence from the quasi-steady state T2 - Journal of Fluid Mechanics UR - http://dx.doi.org/10.1017/jfm.2019.395 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000468628100001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202 UR - https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/on-the-departure-of-nearwall-turbulence-from-the-quasisteady-state/03EF8D8FCB1B5022D9CE0425FFBF6329 UR - http://hdl.handle.net/10044/1/93147 VL - 871 ER -