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REYNOLDS AND NORMAL STRESSES OF TURBULENT BOUNDARY LAYERS AND CHANNEL/PIPE FLOWS AT MODERATE KARMAN NUMBERS

Matthias H. Buschmann
Institut für Luft- und Kältetechnik gGmbH, Bertolt-Brecht-Allee 20, 01309 Dresden, Germany

Mohamed Gad-el-Hak
Virginia Commonwealth University, Mechanical Engineering Richmond, VA 23284-3015, USA

Аннотация

It has been known for a few decades that pure inner scaling does not collapse the characteristic parameters of streamwise stress such as peak value and peak position. Herein we show that this is also true for the Reynolds shear stress and the two other normal stresses. Even more, an analysis of the wall values of streamwise skewness and flatness indicates Karman number dependencies of these parameters. Employing the alternative mixed scaling, which is based on uτ2−αueα instead on uτ2, these dependencies are removed. Based on the general finding that both inner and outer scales are relevant throughout the entire wall layer, a model for the fluctuations is proposed. From this model all stresses and higher-order moments can be built up.