Aeromechanical behavior of selected Douglas-fir

Wind-induced tree sways

“…Measurements have been made using a tower-mounted Gill propeller anemometer (Holbo et al 1980) or a tower-mounted Gill anemometer bivane (Mayer 1979(Mayer , 1985Amtmann 1986). As characteristics of tree sways, Holbo et al (1980) measured the stem deflection of Douglas fir using a pair of stranded stainless steel lines.…”

“…Measurements have been made using a tower-mounted Gill propeller anemometer (Holbo et al 1980) or a tower-mounted Gill anemometer bivane (Mayer 1979(Mayer , 1985Amtmann 1986). As characteristics of tree sways, Holbo et al (1980) measured the stem deflection of Douglas fir using a pair of stranded stainless steel lines. Mayer (1979Mayer ( , 1985 and Amtmann (1986) measured stem accelerations mainly of spruce as characteristics of tree sways from which tree deflections could be derived by the Duhamel integral (Amtmann 1986).…”

“…The experimental methods, such as properties of the measuring systems and the sampling rate (mostly 10 Hz), are described in detail by Holbo et al (1980), Mayer (1985, and Amtmann (1986). The physical basis for analysing data has always been the spectral method.…”

“…Therefore, the spectral method is more useful (Holbo et al 1980;Mayer 1985;Amtmann 1986), where the power spectrum of tree response results from a frequency analysis of the wind speed with respect to windload (Fig. 5).…”

“…The physical relationship, however, between wind forces as a whole, including the dynamic forces of strong winds and storms, and the responses of trees has hardly been investigated in outside experiments, even though it has great importance for forests with regard to storm damage (Woelfle 1936;Geiger 1950). There have been few relevant experimental works, but these include investigations on the Douglas fir (Holbo et al 1980), spruce (Mayer 1985), and spruce as well as pine (Amtmann 1986).…”