Flow around a Living Tree(<Special Issue>Jets, Wakes and Separated Flows)

Flow around a living tree was investigated as basic research of a windbreak forest. A type of conifer, which is named "goldcrest," was used as the test piece in a wind tunnel experiment. The drag coefficient of the living tree was measured in the range of a mean flow velocity of 5〜15m/s. The drag coefficient of the living tree was less than that of a two-dimensional circular cylinder. Because flow passes through the tree's crown which has the permeability of branches and leaves, the drag coefficient was decreased as the flow velocity was increased. Moreover, the flexibility is that the bole of a living tree also plays an important role in drag reduction, bending itself so as to decrease the projected area. In the wake behind the living tree, reverse flow was found at further downstream region than the case of a circular cylinder.