Transitional intermittency in a rough wall boundary layer

Abstract

The transitional intermittency factor distributions were evaluated from the wall friction records acquired in the rough wall boundary layer under free stream turbulence. Important characteristics of by‐pass transition were derived from the factor distributions. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Preliminary results of the conditional analysis of wall friction during laminar‐turbulent transition of a rough wall boundary layer

“…The contribution is a follow-up to the experimental studies of boundary layer (BL) by-pass transition performed earlier in the IT AS CR in Prague. A part of results on transitional intermittency in zero pressure gradient boundary layers on the smooth flat plate and the plate covered by sand paper -grits 60 both under turbulent free stream were reported last year [1,2]. The aim of this study is find some differences in the transition process caused by the surface roughness.…”

“…Thus the duration and the occurrence rate of laminar or turbulent events can give a qualitative notion on the wall roughness effect on spot production and rough estimate on spot or calmed regions "dimension". The description of the experimental set up and methods was given in [1] and more closely in [5] so it is not necessary repeat them. Let us remind only that the wall friction time recording was done in transitional region of the zero pressure gradient boundary layers developing on the smooth plate or on the plate's surface covered with sand paper (grits 60).…”