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Third- and fourth-order mixed moments of turbulent velocity and temperature fluctuations in the atmospheric surface layer

Research paper by R. A. Antonia, A. J. Chambers, E. F. Bradley

Indexed on: 01 Apr '82Published on: 01 Apr '82Published in: Boundary-Layer Meteorology



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, uθ and wθ(u and w are the longitudinal and vertical velocity fluctuations; θ 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, θ Schwarz inequalities, commonly used in the clipping approximation in turbulence modelling, are found to provide bounds for third-order moments of w, θ that are too conservative. More reasonable, tighter, bounds for these moments are given by inequalities obtained by Lumley.