都市風場對氣候品質影響甚鉅,都市中建物漸朝高層化發展,加上人口集中且交通需求量大增,導致都市空氣污染日趨嚴重,其中所形成之街谷型態對都市環境更是帶來許多負面影響。然而,國內都市開發強度管制及建築量體規模控制等相關管制措施,對於都市微氣候之影響仍缺乏討論及規範。 本研究透過計算流體力學(Computational Fluid Dynamics ,CFD)模擬都市風場中氣流變化及污染物質(NO2)分佈狀況。其中以建蔽率及開發強度差異等變因,探討街道峽谷及街道佈局型態之差異對於盛行風場中污染物質堆積分佈現象之影響。結果得知,當街谷地面平均產生交通污染物時,建蔽率及開發強度的差異皆會影響街谷中風速及濃度值變化、污染物堆積位置與高度;街谷中背風處位置污染濃度值高於其迎風處位置。街谷中平均污染濃度值並未因建蔽率或開發強度降低而得到較佳的驅散效果。 都市開發管制方面,單由考量建蔽率或開發強度之改變,對於污染物驅散效果並不顯著;透過其街道佈局型態引入盛行風,以尋求良好的通風策略而增進風廊通風效能、降低污染物質對當地的影響,進而改善都市氣候品質,以期達到生態都市之目標。
Urban wind field has a dramatic effect on the climate. Lately, urban air pollution has become far worse as more high-rises dot the city skyline. Not to mention the population concentration induced increased traffic flow and the negative effects brought on by the street canyon model. However, the effects of urban development and building massing regulations on urban micro-climate are still getting little attention. This study uses Computational Fluid Dynamics (CFD) simulations to describe flow fields and pollutant distribution (NO2). Also, the study focuses on the coverage ratio and development intensity as well as their correlation with different street canyon and urban fabric to understand the accumulation and distribution of pollutants in a wind field. In addition, the study has found that when a street canyon is exposed to traffic pollutants, the coverage ratio and development intensity would change the wind velocity, concentration, pollution accumulation as well as stack height. Moreover, pollution concentration is higher on the leeward side than on the windward side of the street. On top of that, decreased coverage ratio and development intensity cannot improve the average pollution concentration level. The coverage ratio and development intensity have insignificant effect on the dispersion of pollution concentration. On account of that, to improve the urban climate, thus creating an eco-city, needs us to draw solutions such as aligning streets with the prevailing wind, seeking for a better ventilation strategy, and lower the local effect of pollutants.