Third- and fourth-order mixed moments of turbulent velocity and temperature fluctuations in the atmospheric surface layer |
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| Authors: | R A Antonia A J Chambers E F Bradley |
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| Institution: | (1) Department of Mechanical Engineering, University of Newcastle, 2308 Newcastle, N.S.W., Australia;(2) Division of Environmental Mechanics, CSIRO, 2600 Canberra, A.C.T., Australia |
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| Abstract: | Fourth-order mixed moments of velocity and temperature fluctuations, measured within the atmospheric surface layer, are compared with results obtained by assuming the quasi-Gaussian approximation. Standard deviations of the products uw, u and w(u and w are the longitudinal and vertical velocity fluctuations; is the temperature fluctuation) are in good agreement with those obtained using the quasi-Gaussian assumption. Good agreement is also obtained between measured and Gaussian estimates of fourth-order moments including all three fluctuations u, w, Schwarz inequalities, commonly used in the clipping approximation in turbulence modelling, are found to provide bounds for third-order moments of w, that are too conservative. More reasonable, tighter, bounds for these moments are given by inequalities obtained by Lumley. |
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