抄録
The roles of vegetation for environments are well known; a) absorption of CO2 and supply of O2 during the process of photosynthesis, b) production of carbohydrate, as producer in the pyramid of eco-system, c) climate mitigation by the latent heat release and reflection of solar energy radiation (umbrella effect) and d) psychological effects of green for the human. The interaction between air- or water-flow and vegetation promotes the exchanges of momentum, gases and heat between them. In order to understand these processes, the investigation of the turbulence characteristics, large-scale coherent structures are indispensable. The interaction of air- or water-flow and plant canopies resembles partly to the mixing shear layer and partly to the wall boundary layer flows.By the LES numerical simulation, the followings are confirmed : the reliability of the scheme and program by comparing the results for near-wall flow with the standard data, the formation of spanwise oriented long eddies by the inflectional-point instability mechanism in the initial stage of flow, evolving, in the low LAD (Leaf-Area Density) case, into the "roller and ribs" system proposed by Hussain or the double/multiple structure by Hino, and for the case of high LAD into the undulating streamwise streaks which resembles the near wall turbulent structure
