Abstract
The comparison of transitional intermittency distributions in boundary layers on smooth and rough surface is presented. The conditional analysis of the instantaneous wall friction is applied on time records made in transitional boundary layers originating on smooth surface or surface covered by sand paper. Special procedures of measurement and evaluation are applied that allowed evaluations of turbulent and nonturbulent zone averages.
Highlights
The problem of joint action of wall roughness (WR) and free stream turbulence (FST) on the boundary layer development is very broad
Results related to smooth wall layers are marked with grey marks, results related to rough wall layers are plotted with empty marks
The formula is valid at the configuration smooth surface and low FST level γ(ζ) ϭ 1 Ϫ exp[Ϫα(ζ ϩ β)2]
Summary
The problem of joint action of wall roughness (WR) and free stream turbulence (FST) on the boundary layer development is very broad. The Ludwieg and Tillmann empirical curve [4] The accuracy of this procedure is generally weak, namely in rough wall boundary layers, because of the measurement scatter, of a sparse net of measurement, of a slow change of Cf in the streamwise direction, etc. The location of the laminar-turbulent transition region can be estimated from the distributions of characteristics derived from the mean flow measurements, especially if their course is known in laminar and turbulent states. This is the case of the flat plate boundary layer. The location of transitional region was carefully estimated by the diversion of the skin friction coefficient distribution from the Blasius solution [3] and by the attachment of the distribution to
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