基于“风感”的紧凑型城市开放空间风环境实测和CFD模拟比对研究

城市开放空间的风场不仅影响微环境的"风感"舒适度还影响宏观尺度的城市气候。从景感生态学的角度出发,首先阐述"风感"的定义,总结了街道峡谷空间风场的基本规律和特点。运用Kestrel NK4500手持气象站对城市开放空间的风环境进行实测,采用CFD(Computational Fluid Dynamics)模拟软件Fluent 14.0对不含绿地的同一空间进行风环境模拟,通过两者的数据比对来研究紧凑型城市开放空间内绿地对行人高度风场的实际干扰程度。结果发现,紧凑型城市开放空间的"风感"受建筑和绿地空间布局的共同影响。当建筑高于绿地时,风场受建筑的控制;当林带高于建筑时,林带对风环境的影响程度受其疏密度影响。疏密度较高的常绿林带对风向和风速影响很大,而疏密度较低的林带会影响风速,对风向影响不大。影响风速的主要因素是空间围合所形成的空气域,相比实体、多孔介质,空气域对风的阻力要小的多。如铺装、草坪上方的通风廊道是影响行人高度层通风、导风的关键因素。紧凑型空间内的绿地在行人高度应保持通畅以保证通风,并通过建立平面和竖向上的通风、导风廊道体系,促进空气循环。

A comparative study of wind environment measurement and CFD simulation in a compact urban open space based on wind sense

Wind fields in urban open space not only affect the "wind sense" comfort of the micro-environment, but also the urban climate at the macro-scale. From the perspective of Landsenses Ecology, this paper first expounds the definition of "wind sense" and summarizes the basic principles and characteristics of street canyon wind fields. Kestrel NK4500 hand-held weather stations are used to measure the wind environment of urban open space. The CFD (Computational Fluid Dynamics) simulation software, Fluent 14.0, is used to simulate the wind environment in the same space without the green space. The measurement and CFD simulation results are compared to study the actual interference of green space on wind fields at pedestrian height in compact urban open space. It has been found that the "wind sense" of compact urban open space is influenced by the spatial layout of both buildings and green space. When the buildings are higher than the green space, the wind field is dominated by the buildings; when the tree belts are higher than the buildings, the degree of influence on the wind environment is affected by of the tree belts'' density. An evergreen forest belt with high density has a profound influence on wind direction and wind speed, whereas a forest belt with low density affects wind speed, but has little effect on wind direction. The main factor affecting wind speed is the air domain formed by space enclosure. Compared with solid and porous media, the air domain has considerably lower resistance to the wind. Particularly, ventilation corridors above paving and lawns are the key factors affecting ventilation at pedestrian height level. The compact green space at pedestrian height should be kept open to ensure ground ventilation, and air circulation should be promoted by systematically establishing horizontal and vertical ventilation corridors.