About some aspects of the wake flow of a small cypress tree, in a free stream with a power law mean velocity distribution

Abstract

Wind tunnel tests have been conducted on a small slender cypress tree (cupressus macrocarpa), exposed to flows with a power law mean velocity distribution, with an exponent corresponding to a rough urban boundary layer. The purpose of this study was to contribute to the understanding of the nature and evolution of the turbulent motions in the near-wake region of a real tree, by analyzing overall turbulence statistics and instantaneous flow velocities. The paper analyzes qualitatively the downstream evolution of the spatial distributions of functions of the turbulent variables in the wake region. The present experiments describe the features of a relatively small wake region near the canopy 0.5 < x /H < 1.36, with significant variations in the distributions of mean velocities, autocorrelation, power density spectra and turbulence intensity. Aspects of transport processes from the mixing layer regions into the lower wake levels are analyzed. Turbulence characteristics of a relatively “quiet” downstream decreasing internal wake region, located well below the secondary maximum points of the mean velocity distributions, are described.