Mechanical Engineering - Research Publications

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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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    On the validity of Taylor's hypothesis in wall turbulence
    Uddin, A. K. Mesbah ; Perry, A. E. ; MARUSIC, IVAN ( 1997)
    The validity of Taylor’s hypothesis of frozen turbulence has been the issue of much debate, especially when applied to flows with strong shear and high turbulence intensities. In the past, Taylor’s hypothesis was used by various researchers for the quantitative interpretation of the structure angle of the eddies on the basis of double-velocity correlations (eg. Alving et al. [1]) or velocity-wall pressure or velocity-wall shear stress correlations (e.g. Brown & Thomas [2] , Rajagopalan & Antonia [6]. In light of the ambiguity associated with Taylor’s hypothesis, naturally, there are resultant uncertainties in terms of the measured structure angle. Subsequently there is a need to investigate how do these uncertainties effect the structure angle measurements and as well as to examine the validity of Taylor’s hypothesis when applied to two-point double-velocity correlation measurements in an anisotropic shear flow.