Effects of components of the leaf area distribution on drag relations for Cryptomeria japonica and Chamaecyparis obtusa

Abstract

The objectives of this study were to clarify the effects of components of the leaf area distribution on the drag coefficient of crowns and streamlining (e.g., leaf area index; LAI, outline of the crown shape, and clumpiness) and to contribute to the accumulation of data on drag relations by quantifying data for Chamaecyparis obtusa and Cryptomeria japonica. We conducted drag experiments while simultaneously capturing dynamic crown images for 28 Ch. obtusa crowns and 13 Cr. japonica crowns to analyze the relationships between the leaf area distribution components and drag coefficient or streamlining. The static drag coefficient increased with the LAI for Ch. obtusa and with decreasing clumpiness for Cr. japonica. The reduction rate of the static drag coefficient decreased with increasing clumpiness for Ch. obtusa and with a combination of increasing LAI and decreasing clumpiness for Cr. japonica. The reduction rate of the static drag coefficient had a clear relationship with the decreasing rate of the dynamic crown projected area of obstacles (foliage elements, branches, and stems) calculated from captured video images under windy conditions for Cr. japonica, while Ch. obtusa did not show clear relationship between them. The drag coefficients assuming non-porous crown; C max estimated by simple model combining LAI and clumpiness were approximately 1.0 in Ch. obtusa and 0.5 in Cr. japonica and were equivalent to the dynamic drag coefficients from video image under windy condition. The combination of LAI and clumpiness provided simple estimation for drag relations and enable to link crown structure to wind damage easier.

A wind tunnel study of the aerodynamic characteristics of a scaled, aeroelastic, model tree

“…At the same time, the mean base overturning moment coefficients decrease for larger wind speeds, which is discussed further in Section 3.2. This result is also found in wind tunnel tests of broad-leaved species (Cao, et al, 2012;Vollsinger, et al, 2005) and field measurements of broadleaved species (Kitagawa, et al, 2015;Koizumi, et al, 2010).…”

“…There are two main methods to study aerodynamic characteristics of trees. One is field measurements, which have mainly focused on the aerodynamic force coefficients (Grant and Nickling, 1998;Kane and Smiley, 2006;Kitagawa et al, 2015;Koizumi et al, 2010Koizumi et al, , 2016Borisevich and Vikhrenko, 2018;Gonzales et al, 2018) and overall capacity (Gillies et al, 2000;Kane et al, 2008). Estimated aerodynamic forces acting on tree crowns obtained from field measurements are of value; however, are rarely conducted because of the obvious challenge.…”

Aerodynamic properties of green gram sown in different environments in Indo- Gangetic Plains of West Bengal

“…For the LAI value 1.5, the "C d " value was 0.015. This increment of "C d " with LAI was due to clumping character of the green gram canopy (Kitagawa et al, 2015).…”

“…In case of natural turbulent boundary layer, where the temperature gradient is small and having uniform density, the wind profile follows a log law (Dong et al, 2001). The leaf area index, leaf area distribution affect the drag coefficient of different crops (Kitagawa et al, 2015). Masseroni et al (2015) observed a close correlation between the height of the rice crop with "d" and "Z 0 ".…”

A method for measuring the forces acting on a tree trunk using strain gauges

“…However, the wind speed profiles used are virtual and averaged, such as the logarithmic model [ 7 ], which does not express temporal changes of the wind profile. Determination of the drag coefficient is difficult and impractical for use in a forest stand; the drag coefficient of a tree changes with wind speed, crown morphology, and tree species in wind tunnel experiments [ 8 – 12 ] and large variation within individuals are observed in natural winds [ 9 ].…”