Abstract
The purpose of this study is to investigate flow around of a living tree as the basic research of the windbreak forest. A conifer which name is "goldcrest", a kind of garden plant, was used as test piece in the wind tunnel experiment. Drag of a living tree was directory measured by the 6-axis force torque sensor. Drag coefficient of a living tree was less than that of two-dimensional circular cylinder and rectangular plate in the range of mean flow velocity of 5〜15m/s. Because a living tree has two aerodynamics characteristic, the flexibility and the permeability. Branches and leaves of a living tree have a permeability to pass through a wind to reduce the drag. Moreover, the flexibility is that the bole of a living tree bends itself so as to decrease the projected frontal area in the wind. This also plays an important role in drag reduction. Effect of bending of the bole and the permeability of branches and leaves in tree's crown was estimated using visualization technique. The wake profile behind a living tree was also measured by means of the wind tunnel experiment. The reverse flow was found at further downstream region behind a living tree. Because flow passes through the tree crown consisted of branches and leaves, flow velocity was decreased calmly. In being decreased, it makes to retard the development of shear layer vortices.
