In-field Determination Of Drag Through Grass
For A Forest-fire Simulation Model
Author(s)
P. M. Kenney, T. G. Keith, T. T. Ng & R. R. Linn
Abstract
Forest-fire simulation modelers need fluid-drag data for ground vegetation;
however, very little such data is to be found. Further, the gathering of such data
using experimental facilities such as large flumes is time, labor, and equipment
intensive. This paper presents an initial investigation of a plant-drag
measurement procedure which can be carried directly to native plant
communities. Instead of using large flumes and potted plants with load cells
attached, this work will verify that a portable wind tunnel can be used to
determine the difference in total pressure across a stand of vegetation. The total
pressure difference can then be equated to the drag through that stand and a drag
coefficient determined as a function of the Reynolds number. Vegetal parameters
considered in determining a drag coefficient are percentage cover, fractal
dimension, and lacunarity. Vorticity and flow through the plant canopy causing
plant oscillation are not considered because of the limited height of the tunnel
used and because of honeycomb flow straighteners used in the apparatus which
destroy vorticity and alter the velocity profile.
Keywords: plant drag, in-situ data collection, fractals, lacunarity, total pressure,
wind tunnel.
1 Introduction
The need for drag coefficient data for grasses, forbs, etc. (and the lament of the
lack thereof) exists in the studies of water flow in plant-filled, open channels and
cultivated flood plains awash with spring flooding [1], of wind lodging
(overturning) in crops [2, 3], of soil erosion windbreaks, and of inter- and
Keywords
plant drag, in-situ data collection, fractals, lacunarity, total pressure,
wind tunnel.
Related Book
Other papers in this volume
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