WIND DRAG WITHIN A SIMULATED FOREST CANOPY FIELD.
COLORADO STATE UNIV FORT COLLINS FLUID MECHANICS PROGRAM
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The report presents an experimental and analytic study of wind drag within simulated forest canopy fields. The drag coefficients, aerodynamic roughness and wind velocity profiles are studied for various types of forest canopies. Furthermore, a brushy canopy field was studied which simulated the leafy portion of a forest without the tree trunks present. The wind drag force on a single experimental tree was also studied. This information is useful to those who are concerned with diffusion within a canopy in an atmospheric boundary layer. In the course of the study a shear plate was developed which reliably measures a drag force from 0.1 gram to 2000 grams. The function of this plate was successfully validated by testing it in a turbulent flow over a smooth surface. The drag coefficient of a single model tree, which was the same as those used in the simulated forest canopy fields, was compared with prototype conifers. The work found that a plastic model tree has drag coefficients between those for spruce and Douglas fir trees. The variation of the tree drag coefficient among trees of the same type is concluded by a statistical study on a number of plastic trees which have the same amount of foliage but which are different in the arrangement of the tree branches and the tree leaves. Author
- Fluid Mechanics