Power law or logarithmic law? — A data analysis for zero pressure gradient turbulent boundary layers with low Reδ2

Abstract

The paper presents an analysis of two-dimensional zero pressure gradient (ZPG) turbulent boundary layers (TBL) with regard to the application of power laws. Only TBL with low Reynolds number 300 < Reδ2 < 6200 are taken into account. It is found that a certain region of the mean velocity profile can be described with a power law of the formu +=C Pow{*}y +a. This power law region is not a priori identical with the overlap region. An algorithm for the determination of the wall skin friction using the power law is proposed. The method was applied with good result to ZPG TBL and to adverse pressure gradient (APG) TBL. To bridge the gap between the wall and the power law region an approach for the turbulent viscosity is suggested.