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作者

来源

LANDSCAPE AND URBAN PLANNING,Vol.168,P.84-93

语言

英文

关键字

Semi-empirical urban canopy model; Drag force; Urban trees; Landscape planning; Urban wind environment; PEDESTRIAN-LEVEL; OBSTACLE ARRAYS; ROUGH SURFACES; DRAG PARTITION; FLOW; AREAS; VEGETATION; BUILDINGS; CANOPY; TUNNEL

作者单位

[Yuan, Chao] Natl Univ Singapore, Dept Architecture, Sch Design & Environm, Singapore, Singapore. [Norford, Leslie] MIT, Dept Architecture, 77 Massachusetts Ave, Cambridge, MA 02139 USA. [Ng, Edward] Chinese Univ Hong Kong, Sch Architecture, Hong Kong, Hong Kong, Peoples R China. [Ng, Edward] Chinese Univ Hong Kong, Inst Environm Energy & Sustainabil, Hong Kong, Hong Kong, Peoples R China. [Ng, Edward] Chinese Univ Hong Kong, Inst Future Cities, Hong Kong, Hong Kong, Peoples R China. Yuan, C (reprint author), Natl Univ Singapore, Dept Architecture, Sch Design & Environm, Singapore, Singapore. E-Mail: akiyuan@nus.edu.sg; lnorford@mit.edu; edwardng@cuhk.edu.hk

摘要

High-density urban areas are often associated with limited outdoor natural ventilation. Given the growing call for more vegetation in cities, it is important to study the wind resistant of urban trees in order to address outdoor natural ventilation problem in the landscape planning. Currently, Computational Fluid Dynamics (CFD) simulation and wind tunnel experiment can only model the simplified street canyon with roadside trees, at the expense of intensive technical support and high computational cost. Thus, they are mostly for the research purpose, only, and the impact of research outputs on the landscape planning remains low. In this study, we developed a practical semi-empirical model to provide scientific understandings for the landscape planning practice. The new model was developed based on the balance between momentum flux and the drag force of both buildings and trees on air flow. Friction velocity (u(*)) was modeled and validated by existing CFD and wind tunnel data, and effective frontal area density (lambda(ftree)) was estimated by the measured leaf area index. Effects of urban context density and trees (i.e. plant canopy density and typology) on wind environment were clarified. This research correlated the urban density and tree geometry indices with wind speed, thereby enabling planners to calculate trees' effects on airflow using their in-house data. With such new practical tool and understandings, the knowledge-based landscape planning can be conducted to introduce more trees into urban areas, while avoiding negative effects of trees on the outdoor wind environment at cities at the same time.