建築配置形式對戶外空間環境風場之影響

The Effects of Different Urban Street Layouts on Wind Patterns

都市化的現象導致都市快速的發展促使人口不斷向都市聚集，對自然環境造成嚴重的衝擊 與變遷，隨著氣候變遷所面臨的環境問題也愈漸複雜，顯示出都市的發展與氣候的變遷亦息息 相關。而密集的建築配置形式對都市環境風場亦產生影響，包括戶外環境品質及周圍建築物之 室內環境品質，因此都市內環境與生活品質等課題已逐漸成為都市發展的重點。是故，本研究 延續「不同街道尺度對環境風場之影響」之研究，除探討連棟建築型態之街谷流況與通風效能 外，進而探討三種建築配置形式（包括連棟建築、獨棟並排、中庭空間）對戶外空間風環境之影 響。於「不同街道尺度對環境風場之影響」之研究中，已進行計算流體力學（CFD）與現地量測 之數據比對，證實CFD所求得之結果與實測所得之數據相近，以CFD於相關研究具有一定的可 信度，雖兩者之間仍有差異，但是仍屬可接受之合理範圍，此方法仍可於規劃設計階段運用以 增加準確度。因此，本研究延續此數值模擬設定，進行三種建築配置形式之戶外空間物理環境 模擬，分析項目包括平均風速比（U/Ur）與街谷流況。研究結果可知，不論何種街道配置形式， 均呈現出隨街道尺度（H/W）越小，平均風速比（U/Ur）變化越小。以連棟建築而言，於街谷1，隨 著風速越大，街谷內之平均風速比（U/Ur）變化差異越大，隨著街道尺度（H/W）越大（街道寬度越 窄），其街谷內的平均風速比（U/Ur）越不易受基準風速之變化而有所影響；以獨棟併排建築形 式而言，大多呈現出街谷內之平均風速比（U/Ur）不易受基準風速之影響而有所變化，街道尺度 （H/W）越小，街谷內之平均風速比（U/Ur）變化較大，且因所接觸的建築面較窄，導致街谷內風 速變化較為均等，且較不易受基準風速之變化而有所影響；以封閉式中庭而言，平均風速比 （U/Ur）之變化趨勢會因中庭尺度（H/W）越大，變化幅度越小，且中庭內部之環境風場較為穩定， 顯示出受外部環境風場之影響較小。

Urbanization can negatively impact the natural environment, and dense urban layouts influence the urban wind patterns. These influences include the quality of outdoor and indoor environment quality. Hence, the urban environment and living quality are becoming significant issues in the domain of urban design. This study focuses on external flow patterns and ventilation performance in urban wind environments created by different building types (e.g., terrace, detached, courtyard building) and urban street layouts. In our previous investigation, the CFD (computational fluid dynamics) setups were verified by field data. Thus, this study procedure can be applied during the design stage with reasonable accuracy. This study therefore applies CFD simulation for parameter analysis. Three street layouts were analyzed and analyses were based on average wind-speed ratio (u/Ur) and external flow patterns. Change in the average wind-speed ratio is small when the street aspect ratio is small for all urban street layouts. In the first street canyon (upwind), variation in the average ratio depends on the reference wind speed. When the street aspect ratio increases (narrow streets), the correlation between the average wind-speed ratio and reference wind speed is weak. For the layout of detached, the correlation between the average wind-speed ratio and reference wind speed is also weak. Only wide streets in the layout of detached buildings markedly increase the average wind-speed ratio in the canyon. Due to the small area on the windward side of building, wind speed variation in the canyon is small and is only minimally influenced by the reference wind speed. For buildings with courtyards, variation in the average wind-speed ratio decreases as the street aspect ratio increases. The CFD calculation demonstrates that the wind environment in courtyards is generally stable, and only minimally influenced by the external wind environment.