| 摘要: | 近年來氣候變化劇烈引起人類對環境的關注，影響都市氣候之因素眾多，包含密集的建築物、都市中綠地、空氣汙染物等，其中植栽除了美化環境與提供生物棲地外，亦為改善都市異常為氣候之重要手法，植栽具擋風或導風之作用，對都市氣候之調節具一定的效果。此外都市中密集的建築物為影響都市風場重要因素。建築物的結構，對氣流而言是一種障礙物，當風流經建築物時，風速與流向會受建築物阻擋之影響而有所變化，影響對行人風場環境之安全與舒適。因此本研究依據不同喬木條件(樹冠孔隙率、樹冠與喬木高度比、樹型、配置)以及五種喬木與單棟建築物距離為研究對象，探討對風環境之影響。研究將運用實際測量與計算流體力學（Computational Fluid Dynamics，CFD）進行，相關數據以無因次法解析，研究結果將提供未來環境規劃設計植栽配置依據。研究結果顯示，風場因建築物阻擋作用形成的渦漩及逆向流對建築物與喬木之間的區域變化影響複雜，其中擋風成效以散形樹冠最佳，而樹冠孔隙率越小之植栽，有利逆向流穿透，增加風速削減作用，故擋風效果佳。此外喬木樹冠層高度與植栽高度比例為2/3，具最佳擋風效果。
In recent years, severe climate changes have drawn our much attention to environment. There’re many factors that can affect urban climate, including dense buildings, urban green area, air pollutant, etc. Among which, except for beautifying environment and providing habitat for organisms, plantation can also be an important approach to improve abnormal urban climate; in addition, it possesses a windbreak or wind guiding effect with a certain effectiveness of regulating urban climate. Moreover, those dense buildings are a key factor to impact the wind field for urban area. The building structure is an obstacle to airflow, when wind flows through buildings, its velocity and direction will be changed due to buildings’ obstruction, which would cause certain impact on the safety and comfort of wind-filed environment for the pedestrians. As a result, this study based on different tree conditions (canopy porosity, ratio of tree-crown and tree height, tree forms and layout) and the distances between five different trees and their corresponding single building as the research object to investigate their effect on wind environment. This study applied the actual measurement and Computational Fluid Dynamics (CFD) to carry out the research, and adopted the dimensionless method to analyze related data; in addition, the research results will be provided as a reference for the tree layout design of environmental planning in the future. They also showed the changes of the vortex and reverse flow that caused by buildings’ breaking of wind field in the zone between buildings and tree area is very complicated; among which, the umbrella-shaped crown has the best windbreak effect, and smaller canopy porosity will be beneficial for the reverse flowing penetration and increased the reduction of wind velocity thus it has the best windbreak effect. Furthermore, the height ratio of crown canopy and tree is 2/3 that has the best windbreak effect. |
