Anisotropic Turbulence Models for Acoustic Propagation Through the Neutral Atmospheric Surface Layer
Final rept. May-Aug 97
ARMY RESEARCH LAB ADELPHI MD
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Several anisotropic models for the three-dimensional spectra of velocity fluctuations in shear dominated, atmospheric surface layer turbulence are presented and discussed. These models include a generalized Gaussian model, two forms of generalized von Karman models the Kristensen, Lenschow, Kirkegaard, and Courtney model and the Mann model. The distinction between a top-down and bottom up approach to the design of a model is discussed, and how the bottom up approach generally leads to more satisfactory models is shown. The effects of turbulent an isotropy on acoustic propagation are explored by calculating mutual coherence functions MCFs describing the coherence of a propagating acoustic wave for the different models. An isotropy effects have been found that they can be quite significant, even when the separation between the acoustic sensors is small.