2023 Volume 85 Issue 2 Pages 101-114
The increased loads acting on a tree due to wet snow accretion and strong winds cause snow damage to trees, such as stem and branch breakage and uprooting. A structural analysis is employed to predict the initiation of snow damage due to snow accretion, thereby taking into account the loads caused by snow and wind. However, few studies have measured wind loads on trees, and the effect of snow accretion on the drag coefficient is unknown. In this study, wind tunnel testing was conducted to clarify the effect of snow accretion on the drag coefficient of Japanese cedar, which is a major forestry species in Japan. A model of cedar branches and leaves, made from actual material, was placed in a wind tunnel, and snow accretion was artificially generated by supplying wet snow into the wind tunnel while blowing air. The changes in the drag coefficient for different experimental conditions, such as wind speed and the amount of accreted snow, were measured. The results showed that snow accretion had three types of effects: (1) increasing the projection area due to the snow itself, (2) reducing drag force, and (3) inhibiting the decrease in projection area caused by the curvature of the branches and leaves due to wind action. These effects changed the drag coefficient.
