Abstract The influence of thermal stability on the ventilation of a cubic building array is examined via large-eddy simulation. For unstable stratification (with bulk Richardson numbers in the range − 0.5 ≲ Rb 0 ), ventilation timescales decrease as the ground-level heating increases; in particular, the mean tracer age and pollutant retention timescale scale linearly with the mean circulation timescale. For stable stratification ( 0 Rb ≲ 0.3 ), however, the ventilation timescales increase with stronger ground-level cooling even though the mean streamwise wind speed and turbulence kinetic energy remain approximately constant. The ventilation pathway changes for stable stratification because pollutants preferentially escape through the lateral openings rather than the roof level. It is argued that conventional time-averaged turbulence statistics (e.g. Reynolds stresses) provide an incomplete picture of the ventilation mechanism under stable stratification.

中文翻译：

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热稳定性对 3D 建筑阵列通风的影响

摘要 通过大涡模拟研究了热稳定性对立方建筑阵列通风的影响。对于不稳定分层（体积理查森数在 - 0.5 ≲ Rb 0 范围内），通风时间尺度随着地面加热的增加而减少；特别是，平均示踪剂年龄和污染物保留时间尺度与平均循环时间尺度成线性关系。然而，对于稳定分层 ( 0 Rb ≲ 0.3 )，尽管平均流向风速和湍流动能保持近似恒定，但通风时间尺度随着地面冷却的增强而增加。由于污染物优先通过侧向开口而不是屋顶水平逸出，因此通风路径会改变以实现稳定分层。有人认为，传统的时间平均湍流统计（例如 G。雷诺应力）提供了稳定分层下通风机制的不完整图片。