Modeling of Velocity Distributions Inside and Above Tall Crops

Abstract

Velocity distributions inside and above a model crop were investigated. The model crop consisted of flexible plastic strips fastened to the floor of a low speed wind tunnel. The experimental results indicated that at some distance xo downstream from the edge of the roughness cover the velocity profiles were similar inside and also above the cover. The length x0 is discussed. The experimental results for the velocity distribution inside the plant cover were compared with field data obtained from different sources. A presentation of the velocity profiles inside the canopy in non-dimensional form collapsed an field and laboratory data for a given crop type on one curve. The laboratory flow above the crop cover was analysed using a power law form and using the logarithmic velocity distribution law. On the basis of the experimental results it is recommended that a two-tower arrangement of wind velocity measuring devices be used both for the evaluation of the surface shear stress and for checking the establishment of similarity profiles in the field.