关于三维长街谷空气交换能力的讨论

Discussion on Air Exchange Level of Three-Dimensional Long Street Canyons

利用CFD(Computational Fluid Dynamics)技术模拟分析了来流风速、地面粗糙高度、建筑布局及缺口宽度对6种典型布局三维长街谷内外流场的影响,并引入整体换气次数nt和局部换气次数np的概念,评估了街谷的换气能力.研究结果表明:在自模区范围内nt与来流风速大小线性相关;粗糙高度对nt的影响是有限的;建筑布局能够明显改变街谷气流组织结构和换气能力,尤其是上风侧缺口的数量、宽度及缺口之间的相对位置.

Influence of ambient velocity magnitude, roughness height around street canyons, buildings layout and interspaces width on flow field in three dimensional long street canyons of six typical buildings layouts was simulated by CFD （computational fluid dynamics） technique. Total air exchange rate nt and partial air exchange rate np were introduced to evaluate air exchange level of three dimensional street canyons. Results showed that nt varied linearly with ambient wind velocity magnitude in self-simulation area. And nt was affected in a limited extent by the roughness height. Air flow structure and air exchange level were tremendously changed by buildings layout, especially interspaces numbers and width among upwind buildings as well as relative position of all interspaces.