Mechanical Engineering - Research Publications

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Author: Chong, Min × Author: Hutchins, Nicholas × Author: Marusic, Ivan × Start date: 2007 ×

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    Some predictions of the attached eddy model for a high Reynolds number boundary layer
    Nickels, T. B. ; Marusic, I. ; Hafez, S. ; Hutchins, N. ; Chong, M. S. (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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    A comparison of turbulent pipe, channel and boundary layer flows
    Monty, JP ; Hutchins, N ; Ng, HCH ; Marusic, I ; Chong, MS (CAMBRIDGE UNIV PRESS, 2009-08-10)
    The extent or existence of similarities between fully developed turbulent pipes and channels, and in zero-pressure-gradient turbulent boundary layers has come into question in recent years. This is in contrast to the traditionally accepted view that, upon appropriate normalization, all three flows can be regarded as the same in the near-wall region. In this paper, the authors aim to provide clarification of this issue through streamwise velocity measurements in these three flows with carefully matched Reynolds number and measurement resolution. Results show that mean statistics in the near-wall region collapse well. However, the premultiplied energy spectra of streamwise velocity fluctuations show marked structural differences that cannot be explained by scaling arguments. It is concluded that, while similarities exist at these Reynolds numbers, one should exercise caution when drawing comparisons between the three shear flows, even near the wall.