Arrays of buildings with pitched roofs are common in urban and suburban areas of European cities. Large-eddy simulations are performed to predict the boundary-layer flows over flat and pitched-roof cuboids to gain a greater understanding of the impact of pitched roofs on urban boundary layers. The simulation methodology is validated for an array of flat roof cuboids. Further simulations show that changes in the type of grid conformity have a negligible effect on the mean flow field and turbulent stresses, while having a visible, but small, effect on the dispersive stresses for a given packing density. Comparisons are made for flat and \(45^\circ \) pitched roof cuboid arrays at packing densities of 16.7% and 33.3%. The interactions between pitched-roof buildings and their effect on the urban boundary layer are considerably different to those of flat-roof buildings. The pitched roofs at a packing density of 33.3% leads to significant changes in the mean flow field, the Reynolds stresses, and the aerodynamic drag. Further work investigates the effects of changes in turbulence level and atmospheric thermal stratification in the approaching flow. Importantly, in comparison to a flat-roof array, the pitched-roof one at a packing density of 33.3% evidently increase the friction velocity and greatly reduces the effects of stable stratification conditions and changes in inflow turbulence level.

在欧洲城市的市区和郊区，成排的斜屋顶建筑很常见。执行大涡模拟以预测平面和斜屋顶长方体上的边界层流动，以更好地了解斜屋顶对城市边界层的影响。该模拟方法已针对一系列平屋顶长方体进行了验证。进一步的模拟表明，网格一致性类型的变化对平均流场和湍流应力的影响可以忽略不计，同时对给定填充密度的分散应力有明显但很小的影响。对 flat 和\(45^\circ \)进行比较斜屋顶长方体阵列，堆积密度分别为 16.7% 和 33.3%。斜屋顶建筑之间的相互作用及其对城市边界层的影响与平屋顶建筑有很大不同。堆积密度为 33.3% 的斜屋顶导致平均流场、雷诺应力和空气动力阻力发生显着变化。进一步的工作研究了湍流水平变化和大气热分层在接近流中的影响。重要的是，与平屋顶阵列相比，堆积密度为 33.3% 的斜屋顶阵列明显增加了摩擦速度，并大大降低了稳定分层条件和流入湍流水平变化的影响。