A Mathematical Model for Air Flow in a Vegetative Canopy

Abstract

The objectives of this study are to investigate the turbulent transfer of momentum within a vegetative canopy and also to develop a mathematical model which expresses the aerodynamic roughness effects of the surface boundary in terms of the height, density, and drag characteristics of a vegetative canopy. To date three mathematical models have been formulated. The present model reflects both the theoretical and empirical aspects of the two previous models and other available canopy observations. Computed mixing length solutions showed that the mixing length, ?, was nearly constant throughout most of the canopy's vertical extent and also that ? increased linearly with height above the canopy. The computed canopy wind profile solutions verified that the mixing length is nearly constant with height within a mature corn plant canopy and that the simulated canopy wind profiles agreed quite well with the observed canopy wind data of a cornfield. An independent cheek on the model was performed using wind tunnel data for an artificial canopy; once again the simulated canopy wind profiles were in good agreement with the observed data. Example profiles of the mixing length and the canopy wind profiles are presented along with simple scatter diagrams to summarize the analysis of the model data.