Drag coefficient and plant form response to wind speed in three plant species:: Burning Bush (Euonymus alatus), Colorado Blue Spruce (Picea pungens glauca.), and Fountain Grass (Pennisetum setaceum) -: art. no. 4760

[1] Whole-plant drag coefficients (C-d) for three plant species: Burning Bush (Euonymus alatus), Colorado Blue Spruce (Picea pungens glauca.), and Fountain Grass (Pennisetum setaceum) in five different porosity configurations were developed from force versus wind speed data collected with a force balance in a recirculating wind tunnel. The average C-d for the Burning Bush, Colorado Spruce, and Fountain Grass in their untrimmed forms were 0.42 (+/-0.03), 0.39 (+/-0.04), and 0.34 (+/-0.06), respectively. Drag curves (C-d versus flow Reynolds number (R-e) function) for the Burning Bush and Colorado Spruce were found to exhibit, for the lower porosity configurations, a rise to a maximum around flow Reynolds numbers (R-e = rhou(h)h/nu)of 2 x 10(5). Fountain Grass C-d was shown to be dependent upon R-e to values >5 x 10(5). The Burning Bush and Colorado Spruce plants reduced their drag, upon reaching their maxima, by decreasing their frontal area and increasing their porosity. Maximum C-d for these plants occurred at optical porosities of similar to0.20. The Fountain Grass reduced drag at high R-e by decreasing frontal area and porosity. The mechanism of drag reduction in Fountain Grass was continual reconfiguration to a more aerodynamic form as evidenced by continual reduction of C-d with R-e.