Mechanical Engineering - Research Publications
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ItemSome predictions of the attached eddy model for a high Reynolds number boundary layer(Royal Society Publishing, 2007-01)Many flows of practical interest occur at high Reynolds number, at which the flow inmost of the boundary layer is turbulent, showing apparently random fluctuations invelocity across a wide range of scales. The range of scales over which these fluctuationsoccur increases with the Reynolds number and hence high Reynolds number flows aredifficult to compute or predict. In this paper, we discuss the structure of these flows anddescribe a physical model, based on the attached eddy hypothesis, which makespredictions for the statistical properties of these flows and their variation with Reynoldsnumber. The predictions are shown to compare well with the results from recentexperiments in a new purpose-built high Reynolds number facility. The model is alsoshown to provide a clear physical explanation for the trends in the data. The limits ofapplicability of the model are also discussed.
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ItemEvidence of the k1-1 law in a high-Reynolds-number turbulent boundary layer(The American Physical Society, 2005)Dimensional analysis and overlap arguments lead to a prediction of a region in the streamwise velocityspectrum of wall-bounded turbulent flows in which the dependence on the streamwise wave number, k1, isgiven by k 1-1 . Some recent experiments have questioned the existence of this region. In this Letter,experimental spectra are presented which support the existence of the k 1-1 law in a high-Reynolds-numberboundary layer. This Letter presents the experimental results and discusses the theoretical and experimentalissues involved in examining the existence of the k 1-1 law and the reasons why it has proved so elusive.