Estimation Of The Lagrangian Structure Function Constant C0 From Surface-Layer Wind Data |
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| Authors: | D Anfossi G Degrazia E Ferrero SE Gryning MG Morselli S Trini Castelli |
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| Institution: | (1) CNR-Istituto di Cosmogeofisica, Torino, Italy;(2) Universidade Federal de Santa Maria (RS), Brasil;(3) Dip. Scienze Tecn. Avanz., Universita' Piemonte Orientale, Alessandria, Italy;(4) RISO National Laboratory, Roskilde, Denmark;(5) ENEL/SRI Area Ambiente, Milano, Italy |
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| Abstract: | Eulerian turbulence observations, madein the surface layer under unstable conditions (z/L > 0),by a sonic anemometer were used to estimatethe Lagrangian structure function constant O. Twomethods were considered. The first one makes use of arelationship, widely used in the Lagrangian stochasticdispersion models, relating O to the turbulent kineticenergy dissipation rate  , wind velocity variance andLagrangian decorrelation time. The second one employsa novel equation, connecting O to the constant of thesecond-order Eulerian structure function. Beforeestimating O, the measurements were processed in orderto discard non-stationary cases at least to a firstapproximation and cases in which local isotropy couldnot be assumed. The dissipation was estimated eitherfrom the best fit of the energy spectrum in theinertial subrange or from the best fit of the third-orderlongitudinal Eulerian structure function. Thefirst method was preferred and applied to the subsequentpart of the analysis. Both methods predict thepartitioning of O in different spatial components as aconsequence of the directional dependence of theEulerian correlation functions due to the isotropy.The O values computed by both methods are presented anddiscussed. In conclusion, both methods providerealistic estimates of O that compare well withprevious estimations reported in the literature, evenif a preference is to be attributed to the second method. |
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| Keywords: | Lagrangian and Eulerian statistics Structure functions Autocorrelation functions Energy spectra Surface layer |
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