Abstract In this paper non-neutral approaching flows were employed in a meteorological wind tunnel on a regular urban-like array of rectangular buildings. As far as stable stratification is concerned, results on the flow above and inside the canopy show a clear reduction of the Reynolds stresses and an increment of the Monin-Obukhov length up to 80%. The roughness length and displacement height were also affected, with a reduction up to 27% for the former and an increment up to 5% for the latter. A clear reduction of the turbulence within the canopy was observed. In the convective stratification cases, the friction velocity appears increased by both the effect of roughness and unstable stratification. The increased roughness causes a reduction in the surface stratification, reflected in an increase of the Monin-Obukhov length, which is double over the array compared to the approaching flow. The effect on the aerodynamic roughness length and displacement height are specular to the SBL case, an increase up to 55% of the former and a reduction of the same amount for the latter.

中文翻译：

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城市阵列中稳定的对流边界层流动

摘要 在本文中，非中性接近流被用于气象风洞中的矩形建筑物的规则城市状阵列。就稳定分层而言，冠层上方和内部的流动结果显示雷诺应力明显降低，Monin-Obukhov 长度增加了 80%。粗糙度长度和位移高度也受到影响，前者减少了 27%，后者增加了 5%。观察到天篷内的湍流明显减少。在对流分层情况下，摩擦速度似乎因粗糙度和不稳定分层的影响而增加。粗糙度的增加导致表面分层的减少，反映在 Monin-Obukhov 长度的增加上，与接近的流相比，这是阵列的两倍。对空气动力学粗糙度长度和位移高度的影响在 SBL 情况下是镜面反射的，前者增加了 55%，后者减少了相同的数量。